Poté, co jsem ze seznamu abstraktů vyřadil ptáky (kteří mají díky více než desítce tisíc žijících zástupců nefér výhodu), se ukázal trend, který je patrný už od začátku letošního roku: naprostá převaha sauropodomorfů všech tvarů a fylogenetických pozic. Jelikož dnešní sbírka zahrnuje rekordní počet 31 abstraktů, bylo nemožné napsat o všech; vybral jsem pouze ty, které mi připadají nejzajímavější.
Cabreira et al. (2011) popisují z členu Alemoa souvrství Santa Maria (Brazílie) částečnou kostru nového sauropodomorfa, zahrnující velkou část lebky a elementy páteře i končetin a datovanou do doby před 230 až 228 miliony let, tedy do pozdního karnu. Přestože řada elementů nebyla vyproštěna z bloku jílovce, v němž byla fosilie vyzdvihnuta, autoři v něm dokázali identifikovat jedinečnou kombinaci znaků (o autapomorfiích nicméně nepadla ani zmínka), která podle jejich názoru ospravedlňuje vztyčení nového taxonu. Ten dostal jména Pampadromaeus barberenai: prenomen je složen ze slov "pampa" (jihoamerická step) a latinizované verze řeckého slova δρομεύς, znamenající "běžec". Přívlastek barberenai byl pak nové fosilii udělen na počest brazilského paleontologa Mária Barbereny. Patří mezi ně: hlavice zabírající přes dvě třetiny délky stehenní kosti; předčelistní kost s krátkým subnariálním ("podnozderním") výběžkem, vydutý spodní okraj kontaktu mezi předčelistní kostí a horní čelistí (maxillou); první zuby na předčelistní i zubní kosti zůstávající na okraji čelistí, místo toho, aby byly posunuty dovnitř směrem od tváří; zubní korunky posazené nejvíce vepředu postrádající zoubkování, a to ve spodní i horní čelisti; kopinatý tvar a hrubé zoubkování většiny zubů; křížové obratle s hlubokými žebry; stehenní kost s dobře vyvinutým chocholíkovým šelfem (trochanteric shelf); holenní kost výrazně delší než stehenní. Mezi další zajímavé anatomické znaky nového sauropodomorfa patří zvláštní skloubení horní čelisti s předčelistní kostí, které vytváří v profilu horní čelisti jakýsi zářez, podobný tzv. subnariální mezeře některých teropodů a dobře viditelný na fotografii níže. Zde však tuto mezeru zaplňují zuby, zatímco teropodi v ní mají dobře patrnou mezeru (diastemu). Stejně jako u panfágie a na rozdíl od odvozenějších sauropodomorfů předčelní kost (prefrontál) postrádá plošku, přikrývající zvenku kost slznou. Zvláštností je 15 zakrnělých zoubků na kosti křídlové, vytvářející část kostěného patra; kromě pampadromea zde mají zuby už jen Eoraptor a letos popsaný Eodromaeus (Martinez et al. 2011).
Na celé práci mě poněkud irituje opakované užívání termínu "stem-sauropodomorph". Začal s tím Langer (2003), který takto označil saturnálii, protože ji odkryl mimo klad tvořený sauropody a všemi dosud známými "prosauropody". Už tehdy existovalo silné podezření, že "prosauropodi" jsou ve skutečnosti parafyletickou sérií taxonů čím dál tím vzdálenějších od odvozených, monofyletických sauropodů, a pozdější fylogenetické analýzy (hlavně od Adama Yatese) jej jenom potvrdily. Saturnalia je sauropodům prostě ještě o něco vzdálenější, ale vyřazovat ji kvůli tomu ze sauropodomorfů, skupiny, pro kterou už tehdy existovala praktická branch-based definice (podle níž tam patří všechno, co má blíž k diplodokovi než k vrabci), nedává smysl: pak bychom museli vymýšlet nová a nová jména pokaždé, když objevíme něco ještě bazálnějšího. I kdybychom ale přijali Langerovu definici sauropodomorfů (odpovídající zřejmě něčemu Yatesově Plateosauria, tj. Plateosaurus, Diplodocus, jejich poslední společný předek a všichni potomci tohoto předka), pořád by tato skupina nemohla mít žádnou stem-group, jelikož ty jsou definovány úplně jinak, a na kompletně vymřelé skupiny je nelze aplikovat.
Oceňuji naopak zajímavý přístup, kteří autoři zvolili k nalezení pampadromeovy pozice na dinosauřím fylogenetickém stromě: místo toho, aby jej dosadili do jedné již existující matrice (kterou by snad v pár znacích doplnili či poopravili), šoupli jej hned do čtyř analýz, které se touto oblastí stromu zabývaly. Použity byly matrice z Martineze et al. 2011 (popis eodromea, poprvé odhalila sauropodomorfního eoraptora), Ezcurry 2010 (popis chromogisaura, poprvé odkryl "guaibasauridy", slabě podložený monofyl na bázi sauropodomorfů, zahrnující mj. i dosud teropodního guaibasaura), Martineze a Alcobera 2009 (popis panfágie) a Nesbitta et al. 2010 (popis asilisaura). Výsledky jsou vidět níže. Zatímco data z Ezcurry (2010) a Martineze s Alcoberem (2009) vedla k tomu, že se základna sauropodomorfů změnila v polytomii, Nesbitt et al. (2010) a Martinez et al. (2011) poskytli navzájem konfliktní topologie, v němž má Pampadromaeus buď blíž (Martinez), nebo naopak dál (Nesbitt) než Saturnalia. Skoro zajímavější je tak pozorovat, co zahrnutí nového taxonu udělá s dosavadními topologiemi. Cabreira a spol. také zmiňují, že to málo, na čem se analýzy shodnou (tedy že Pampadromaeus je opravdu hodně bazální sauropodomorf), nemá příliš vysokou statistickou podporu a opírá se o znaky, které jsou buď vysoce homoplastické, nebo u většiny zahrnutých taxonů nemohou být zjištěny. Analýzy také odkrývají četné pampadromeovy autapomorfie (nakonec na ně tedy přece došlo), ale vždy jde o znaky vykazující jistou míru homoplazie; opravdu unikátní pro pampadromea není žádný. Situaci komplikuje zmatečná směska sauropodomorfních apomorfií, homoplazií vůči teropodům a dinosauřích či dinosauromorfních pleziomorfií, jimiž se Pampadromaeus vyznačuje. Nejinak jsou na tom ovšem herrerasauři, Eoraptor a Guaibasaurus, kteří v testovaných matricích střídavě přeskakovali mezi sauropodomorfy, teropody a bazálními (non-eusaurischianními, kde Eusaurischia = Sauropodomorpha + Theropoda) plazopánvými. Podle Cabreiry jde možná o jednu z nejobtížněji zrekonstruovatelných oblastí dinosauřího stromu života vůbec, vzhledem k tomu, že informativní znaky se zde vyvíjely velice rychle a bazální zástupci všech tří skupin si byli navzájem velice podobní (středně velcí, dvounozí všežravci).
Apaldetti et al. (2011) rovněž popisují bazálního sauropodomorfa, byť tentokrát přece jen o něco odvozenějšího. Leyeseaurus marayensis byl popsán na základě kostry s označením PVSJ 706, zahrnující nekompletní lebku, části krční a ocasní páteře, elementy ramenního i pánevního pletence, levou kost pažní a distální kosti levé nohy. Fosilie pocházejí ze souvrství Quebrada del Barro, nacházejícím se v severozápadní Argentině (provincie San Juan). Jeho stáří je poměrně problematické; odhadnuto bylo na stupeň nor (svrchní trias), ale podklady pro toto datování nejsou nijak pevné a fylogenetická pozice leyesaura by spíš podporovala stáří spodnojurské. Diagnóza nového taxonu obsahuje jak autapomorfie, tak i jedinečnou kombinaci znaků. První kategorie zahrnuje: ostrý úhel svíraný vzestupným výběžkem horní čelisti (maxilly) a zubní řadou, o velikosti asi 50° (u všech ostatních bazálních sauropodomorfů 60° až 90°); protáhlé krční obratle, přičemž u obratlového centra šestého z nich dosahuje poměr délky ku výšce více než 5 (u ostatních bazálních sauropodomorfů 3 až 4); a konečně proximální kloubící povrch III. nártní kosti ohnutý až na mediální (= vnitřní, orientovanou směrem k podélné ose těla) stranu kosti, kde vytváří jakýsi šelf. Pod ním je dále patrná hluboká, protáhlá jamka. Všechny tyto jedinečné znaky autoři navíc podrobně diskutují v sekci Discussion, kde dále rozebírají jejich odlišnosti od podobných útvarů na kostrách jiných sauropodomorfů a kde zmiňují i několik dalších kandidátů na leyesaurovy autapomorfie.
Popis leyesaurovy morfologie je daleko podrobnější než v případě pampadromea; autoři jej srovnávají jak s nejbazálnějšími sauropodomorfy typy panfágie, tak i s pokročilejšími zástupci "prosauropodního" gradu, jako jsou plateosauridi, massospondylidi nebo Melanorosaurus. Z leyesaurových anatomických znaků by snad šlo vypíchnout lehce heterodontní (různozubý) chrup, tvořený listovitě tvarovanými zuby výrazně zúženými mezi kořenem a korunkou. Ty na předčelistní kosti jsou nejdelší, mají asymetrické přední a zadní okraje a postrádají zoubkování. Zuby v horní čelisti jsou také zvláštní výrazným vyboulením na labiální (k tvářím orientované) straně, vyvinutým podstatně silněji než u jiných bazálních sauropodomorfů, jako jsou Anchisaurus, Massospondylus nebo Plateosaurus. Stejně tak leyesaura od těchto zvířat odlišuje kýl na spodní straně přední části krčních obratlů 3 až 6 a na celé spodní straně obratle 7, který jej naopak přibližuje yunnanosaurovi a tekodontosaurovi.
Ke zjištění leyesaurovy fylogenetické pozice byla použita matrice z Yatese et al. (2010), doplněná i o ty nejnovější objevy na poli bazálních sauropodomorfů: adeopapposaura, seitaada, chromogisaura, ignavusaura a sarahsaura. Výsledná matrice, sestávající z 54 taxonů a 361 morfologických znaků (z nichž 36 bylo vícestavových a seřazených) byla analyzována metodou nejvyšší parsimonie, která odkryla 18 optimálních stromů. Leyesaurus na nich konzistentně zaujímal pozici sesterského taxonu vůči adeopapposaurovi v rámci kladu Massospondylidae, odvozené skupiny již poměrně blízké sauropodům. Klad (Leyesaurus + Adeopapposaurus) podpořilo celkem 5 jednoznačných synapomorfií ze všech částí kostry, testy podpory ale nevyšly nijak zvlášť dobře: hodnota bootstrapu je pouhých 49% a k rozpadu kladu by stačil pouhý jeden krok navíc. Ani skupina zahrnující leyesaura, adeopapposaura a massospondyla na tom není o moc lépe. Za zmínku stojí, že massospondylidi jsou v tomto fylogenetickém rozboru rozsáhlejší, než tomu bylo u Yatese (2007), ale nezahrnují seitaada, kterého v rámci massospondylidů vykryli Sertich & Loewen (2010). Ten má nyní blíže k sauropodům (viz kladogram níže). Vrátit ho na jeho původní pozici by ovšem vyžadovalo pouhé 4 kroky navíc, což oproti nejúspornějším stromům s 1301 kroky nepředstavuje statisticky signifikantní rozdíl. Změnila se i pozice sarahsaura a ignavusaura: ti spolu nyní formují přesvědčivý klad podpořený 9 synapomorfiemi, jehož rozbití by stálo 7 až 9 kroků v závislosti na tom, kde bychom chtěli, aby Sarahsaurus a Ignavusaurus skončili. (Pro přehled: Rowe et al. [2010] odkryli sarahsaura v závislosti na použité matrici buď jako velice bazálního, non-plateosauřího sauropodomorfa, nebo jako bazálního zástupce monofyletických prosauropodů.)
Svůj článek autoři uzavírají s tím, že nové objevy, jaké představuje Glacialisaurus, Adeopapposaurus nebo třeba právě Leyesaurus, v kombinaci s koloradisaurovým přeřazením do massospondylidů činí tento klad sauropodomorfů jedním z nejrozmanitějších, který na jižní polokouli v té době existoval; na jižní polokouli se ovšem jeho výskyt neomezoval. Další nové objevy, jako Seitaad, Ignavusaurus či Sarahsaurus zase ukazují, že mezi massopody (klad vznikající posledním společným předkem massospondylidů a sauropodů) patřila i zvířata, která nemůžeme zařadit do žádného z dosud rozeznávaných "kladů vyššího řádu", jako jsou massospondylidi, riojasauridi a anchisauři.
To Royo-Torres et al. (2011) popisují nový exemplář tastavinsaura, titanosauriforma, kterého popsali Canudo et al. (2008), o čemž jsem napsal na starou verzi blogu. Nová kostra, od tohoto taxonu teprve druhá, pochází ze souvrství Forcall (španělská provincie Turuel), datovaného do raného aptu, tj. do doby před zhruba 120 miliony let. Sauropod, z nějž se dochovalo několik žeber, část pánevního pletence, kost vřetenní a kompletní zadní končetina, žil v nízce položeném, přímořském prostředí. Objev vedl nejen k revizi původní tastavinsaurovy diagnózy, ale také k odhalení cedarosaura a venenosaura coby jeho nejbližších příbuzných. Výsledný klad nese již od roku 2009 jméno Laurasiformes (Royo-Torres 2009), které naznačuje jeho místo původu – vznikl zde zřejmě někdy ve svrchní juře jako součást širší titanosauriformní vývojové radiace.
Mannion et al. (2011) revidují dinheirosaura, svrchnojurského portugalského sauropoda z kladu Diplodocoidea. Krom potvrzení jeho validity na základě 3 jedinečných odvozených znaků prezentují i důkladnou fylogenetickou analýzu, v níž Dinheirosaurus vyšel jako sesterská skupina severoamerického giganta supersaura. Tato pozice je nicméně poměrně labilní a pouhé 4 kroky navíc by stačili k odsunutí dinheirosaura mezi bazální diplodokoidy, což by vysvětlilo přítomnost primitivních znaků typu nerozdvojených neurálních trnů na předkřížových obratlech. Nejbazálnějším zástupcem rebbachisauridů – skupiny bazálních diplodokoidů, mezi něž patří třeba i bizarní Nigersaurus s tlamou podobnou vysavači – se stal Amazonsaurus. Argentinský Zapalasaurus unikl z rovněž jihoamerického kladu Limaysaurinae, což poněkud komplikuje rebbachisauridí biogeografii. Jeden exemplář dříve přiřazený k dinheirosaurovi podle Manniona a spol. vykazuje silnou podobnost s jiným diplodokidem, apatosaurem, a naznačuje tak, že v portugalské svrchní juře žilo více diplodokoidů vedle sebe. Pokud by hypotéza o dinheirosaurově příbuzenství se supersaurem byla správná, šlo by o další podporu pro existenci svrchnojurského pevninského spojení mezi Evropou a Severní Amerikou, které zřejmě využily i další skupiny sauropodů: existují určité slabé indicie o evropských rebbachisauridech, které ovšem vyžadují další výzkum.
Santucci a de Arruda-Campos revidují jinou, podstatně užší skupinu: klad Aeolosaurini, odvozené titanosaury blízce příbuzné saltasauridům, jejichž vnitřní diverzita v posledních letech rapidně vzrostla: o popisu panamerikansaura (Calvo & Porfiri 2010) jsem napsal i na blogu, stejně jako o letošní revizi éolosaura (Candeiro 2011). Nyní přichází popis dalšího, v pořadí už třetího podtaxonu éolosaura, pojmenovaného jako A. maximus. Kromě éolosaurových synapomorfií disponuje i dvěma unikátními znaky, totiž dobře vyvinutým hrbolem pod kloubící plochou hemálních oblouků ("chevronů") obratlů z přední a střední části ocasu a postranním vyboulením distální části kloubícího výběžku hemálních oblouků zprostřed zadního úseku ocasní páteře. Nová diagnóza kladu Aeolosaurus nepodporuje zahrnutí gondwanatitana, které navrhovali Santucci & Bertini (2001); oddělení obou taxonů prosazoval také Candeiro (2011). Fylogenetická analýza odkryla A. maximus jako sesterský taxon k dosavadním éolosaurům (A. colhuehuapensis a A. rionegrinus). Nejbližším příbuzným výsledné skupiny je pak Gondwanatitan a mezi éolosaurininy patří ještě Rinconsaurus, Maxakalisaurus a Panamericansaurus. Santucci a de Arruda-Campos také stanovují stáří svrchních vrstev souvrství Adamantina a spodních vrstev souvrství Marília, odkud pocházejí brazilské pozůstatky éolosaurininů, a to na kampán až maastricht.
Poslední z abstraktů, o němž se rozepíšu podrobněji, se týká sauropodních migrací a stojí za něm Fricke et al. (2011). Ve severoamerickém souvrství Morrison, pocházejícím ze svrchní jury, žili sauropodi v nížinách a záplavových plošinách podél řek, které byly každoročně zasaženy obdobím sucha. Tehdy mohli obří býložravci pocítit výrazný nedostatek potravy i vody, což činí jejich hojný výskyt v morrisonské pánvi obtížně pochopitelným. Na základě analogií s dnešními velkými býložravými savci byly jako možné řešení navrženy sezónní migrace za vodou i potravou, přímé doklady ale chyběly. Fricke et al. (2011) to nyní napravují. Srovnávají hladiny kyslíkových izotopů v zubní sklovině kamarasaura s uhličitany zformovanými v různých prostředích a zaznamenávají střídavé vzestupy a poklesy, dokládající sezónní přesun do výše položených oblastí. Podle autorů tyto důkazy přispějí k porozumění úlohy, kterou každoroční migrace hrála v ekologii a evoluci sauropodů.
Jako bonus bych z dnešního seznamu vypíchl studie zabývající se velice specifickou oblastí dinosauří anatomie, např. práci Boyda a spol. o mezizubních destičkách ptakopánvých nebo Otera a spol. o hemálních obloucích sauropodů. Popsána je i celá řada nových taxonů: z těch výše nezmíněných jsou to Thescelosaurus assiniboiensis, Saurolophus morrisi, Ratchasimasaurus suranareae a Yueosaurus tiantaiensis; nemluvě o tom, že jsem záměrně vynechal popis huaxiosaura, 18,7 metrů dlouhého (!) ornitopoda, jehož popis je tak strašný, že působí trochu jako paleontologická verze Sokalovy aféry: recyklovaný abstrakt má téměř každé vědecké jméno špatně napsané a uvnitř se skrývá rekonstrukce, která jako kdyby vylezla z 19. století.
Apaldetti C, Martinez RN, Alcober OA, Pol D 2011 A new basal sauropodomorph (Dinosauria: Saurischia) from Quebrada del Barro Formation (Marayes-El Carrizal Basin), Northwestern Argentina. PLoS ONE 6(11): e26964
Cabreira et al. (2011) popisují z členu Alemoa souvrství Santa Maria (Brazílie) částečnou kostru nového sauropodomorfa, zahrnující velkou část lebky a elementy páteře i končetin a datovanou do doby před 230 až 228 miliony let, tedy do pozdního karnu. Přestože řada elementů nebyla vyproštěna z bloku jílovce, v němž byla fosilie vyzdvihnuta, autoři v něm dokázali identifikovat jedinečnou kombinaci znaků (o autapomorfiích nicméně nepadla ani zmínka), která podle jejich názoru ospravedlňuje vztyčení nového taxonu. Ten dostal jména Pampadromaeus barberenai: prenomen je složen ze slov "pampa" (jihoamerická step) a latinizované verze řeckého slova δρομεύς, znamenající "běžec". Přívlastek barberenai byl pak nové fosilii udělen na počest brazilského paleontologa Mária Barbereny. Patří mezi ně: hlavice zabírající přes dvě třetiny délky stehenní kosti; předčelistní kost s krátkým subnariálním ("podnozderním") výběžkem, vydutý spodní okraj kontaktu mezi předčelistní kostí a horní čelistí (maxillou); první zuby na předčelistní i zubní kosti zůstávající na okraji čelistí, místo toho, aby byly posunuty dovnitř směrem od tváří; zubní korunky posazené nejvíce vepředu postrádající zoubkování, a to ve spodní i horní čelisti; kopinatý tvar a hrubé zoubkování většiny zubů; křížové obratle s hlubokými žebry; stehenní kost s dobře vyvinutým chocholíkovým šelfem (trochanteric shelf); holenní kost výrazně delší než stehenní. Mezi další zajímavé anatomické znaky nového sauropodomorfa patří zvláštní skloubení horní čelisti s předčelistní kostí, které vytváří v profilu horní čelisti jakýsi zářez, podobný tzv. subnariální mezeře některých teropodů a dobře viditelný na fotografii níže. Zde však tuto mezeru zaplňují zuby, zatímco teropodi v ní mají dobře patrnou mezeru (diastemu). Stejně jako u panfágie a na rozdíl od odvozenějších sauropodomorfů předčelní kost (prefrontál) postrádá plošku, přikrývající zvenku kost slznou. Zvláštností je 15 zakrnělých zoubků na kosti křídlové, vytvářející část kostěného patra; kromě pampadromea zde mají zuby už jen Eoraptor a letos popsaný Eodromaeus (Martinez et al. 2011).
ULBRA-PVT016, holotyp pampadromea. Dostupné lebeční elementy jsou podle potřeby zrcadlově otočeny, aby byl pohled zboku co nejkompletnější. a) pravá předčelistní kost a maxilla, b) pravá čelní kost při pohledu zespoda, c) pravá kost jařmová, d) pravá kost předčelní, e) pravá kost zaočnicová s levou kostí šupinovou, f) levá temenní kost při pohledu zespoda, g) levá kost křídlová při pohledu zespoda, h) levá kost zubní, i) zadní část pravé spodní čelisti při pohledu z vnitřní strany. Zkratky: (a) kost úhlová, (aof) předočnicová jamka, (ar) artikular, (d) kost zubní, (emf) vnější mandibulární okno, (en) vnější nozdry, (f) kost čelní, (l) kost slzná, (m) maxilla, (n) kost nosní, (nf) nosní jamka, (p) kost temenní, (pa) preartikular, (pf) kost předčelní, (pm) kost předčelistní, (pmd) promaxillární prohlubeň, (po) kost zaočnicová, (q) kost čtvercová, (sa) kost nadúhlová, (sq) kost šupinová. (Zdroj: Cabreira et al. 2011: Figure 2)
Na celé práci mě poněkud irituje opakované užívání termínu "stem-sauropodomorph". Začal s tím Langer (2003), který takto označil saturnálii, protože ji odkryl mimo klad tvořený sauropody a všemi dosud známými "prosauropody". Už tehdy existovalo silné podezření, že "prosauropodi" jsou ve skutečnosti parafyletickou sérií taxonů čím dál tím vzdálenějších od odvozených, monofyletických sauropodů, a pozdější fylogenetické analýzy (hlavně od Adama Yatese) jej jenom potvrdily. Saturnalia je sauropodům prostě ještě o něco vzdálenější, ale vyřazovat ji kvůli tomu ze sauropodomorfů, skupiny, pro kterou už tehdy existovala praktická branch-based definice (podle níž tam patří všechno, co má blíž k diplodokovi než k vrabci), nedává smysl: pak bychom museli vymýšlet nová a nová jména pokaždé, když objevíme něco ještě bazálnějšího. I kdybychom ale přijali Langerovu definici sauropodomorfů (odpovídající zřejmě něčemu Yatesově Plateosauria, tj. Plateosaurus, Diplodocus, jejich poslední společný předek a všichni potomci tohoto předka), pořád by tato skupina nemohla mít žádnou stem-group, jelikož ty jsou definovány úplně jinak, a na kompletně vymřelé skupiny je nelze aplikovat.
Oceňuji naopak zajímavý přístup, kteří autoři zvolili k nalezení pampadromeovy pozice na dinosauřím fylogenetickém stromě: místo toho, aby jej dosadili do jedné již existující matrice (kterou by snad v pár znacích doplnili či poopravili), šoupli jej hned do čtyř analýz, které se touto oblastí stromu zabývaly. Použity byly matrice z Martineze et al. 2011 (popis eodromea, poprvé odhalila sauropodomorfního eoraptora), Ezcurry 2010 (popis chromogisaura, poprvé odkryl "guaibasauridy", slabě podložený monofyl na bázi sauropodomorfů, zahrnující mj. i dosud teropodního guaibasaura), Martineze a Alcobera 2009 (popis panfágie) a Nesbitta et al. 2010 (popis asilisaura). Výsledky jsou vidět níže. Zatímco data z Ezcurry (2010) a Martineze s Alcoberem (2009) vedla k tomu, že se základna sauropodomorfů změnila v polytomii, Nesbitt et al. (2010) a Martinez et al. (2011) poskytli navzájem konfliktní topologie, v němž má Pampadromaeus buď blíž (Martinez), nebo naopak dál (Nesbitt) než Saturnalia. Skoro zajímavější je tak pozorovat, co zahrnutí nového taxonu udělá s dosavadními topologiemi. Cabreira a spol. také zmiňují, že to málo, na čem se analýzy shodnou (tedy že Pampadromaeus je opravdu hodně bazální sauropodomorf), nemá příliš vysokou statistickou podporu a opírá se o znaky, které jsou buď vysoce homoplastické, nebo u většiny zahrnutých taxonů nemohou být zjištěny. Analýzy také odkrývají četné pampadromeovy autapomorfie (nakonec na ně tedy přece došlo), ale vždy jde o znaky vykazující jistou míru homoplazie; opravdu unikátní pro pampadromea není žádný. Situaci komplikuje zmatečná směska sauropodomorfních apomorfií, homoplazií vůči teropodům a dinosauřích či dinosauromorfních pleziomorfií, jimiž se Pampadromaeus vyznačuje. Nejinak jsou na tom ovšem herrerasauři, Eoraptor a Guaibasaurus, kteří v testovaných matricích střídavě přeskakovali mezi sauropodomorfy, teropody a bazálními (non-eusaurischianními, kde Eusaurischia = Sauropodomorpha + Theropoda) plazopánvými. Podle Cabreiry jde možná o jednu z nejobtížněji zrekonstruovatelných oblastí dinosauřího stromu života vůbec, vzhledem k tomu, že informativní znaky se zde vyvíjely velice rychle a bazální zástupci všech tří skupin si byli navzájem velice podobní (středně velcí, dvounozí všežravci).
Fylogenetická pozice pampadromea podle čtyř různých datových matric specializovaných na bazální plazopánvé dinosaury. Všimněme si, že v Ezcurrovi (2010) způsobil roztržení dřívějších monofyletických guaibasauridů, jejichž podpora stejně nikdy nebyla zvláště silná. Tečkované čáry a podtržené písmo značí non-eusaurischianní plazopánvé (stojící jak mimo teropody, tak mimo sauropodomorfy), šedé linky a písmo označuje sauropodomorfy; černé linky s písmem zase teropody. Autoři aplikovali jméno Sauropodomorpha v dosti obskurním, omezeném významu, tím se ale nenechme zmást: patří tam vše, co je vyznačeno šedě. (Zdroj: Cabreira et al. 2011: Figure 3)
Apaldetti et al. (2011) rovněž popisují bazálního sauropodomorfa, byť tentokrát přece jen o něco odvozenějšího. Leyeseaurus marayensis byl popsán na základě kostry s označením PVSJ 706, zahrnující nekompletní lebku, části krční a ocasní páteře, elementy ramenního i pánevního pletence, levou kost pažní a distální kosti levé nohy. Fosilie pocházejí ze souvrství Quebrada del Barro, nacházejícím se v severozápadní Argentině (provincie San Juan). Jeho stáří je poměrně problematické; odhadnuto bylo na stupeň nor (svrchní trias), ale podklady pro toto datování nejsou nijak pevné a fylogenetická pozice leyesaura by spíš podporovala stáří spodnojurské. Diagnóza nového taxonu obsahuje jak autapomorfie, tak i jedinečnou kombinaci znaků. První kategorie zahrnuje: ostrý úhel svíraný vzestupným výběžkem horní čelisti (maxilly) a zubní řadou, o velikosti asi 50° (u všech ostatních bazálních sauropodomorfů 60° až 90°); protáhlé krční obratle, přičemž u obratlového centra šestého z nich dosahuje poměr délky ku výšce více než 5 (u ostatních bazálních sauropodomorfů 3 až 4); a konečně proximální kloubící povrch III. nártní kosti ohnutý až na mediální (= vnitřní, orientovanou směrem k podélné ose těla) stranu kosti, kde vytváří jakýsi šelf. Pod ním je dále patrná hluboká, protáhlá jamka. Všechny tyto jedinečné znaky autoři navíc podrobně diskutují v sekci Discussion, kde dále rozebírají jejich odlišnosti od podobných útvarů na kostrách jiných sauropodomorfů a kde zmiňují i několik dalších kandidátů na leyesaurovy autapomorfie.
Popis leyesaurovy morfologie je daleko podrobnější než v případě pampadromea; autoři jej srovnávají jak s nejbazálnějšími sauropodomorfy typy panfágie, tak i s pokročilejšími zástupci "prosauropodního" gradu, jako jsou plateosauridi, massospondylidi nebo Melanorosaurus. Z leyesaurových anatomických znaků by snad šlo vypíchnout lehce heterodontní (různozubý) chrup, tvořený listovitě tvarovanými zuby výrazně zúženými mezi kořenem a korunkou. Ty na předčelistní kosti jsou nejdelší, mají asymetrické přední a zadní okraje a postrádají zoubkování. Zuby v horní čelisti jsou také zvláštní výrazným vyboulením na labiální (k tvářím orientované) straně, vyvinutým podstatně silněji než u jiných bazálních sauropodomorfů, jako jsou Anchisaurus, Massospondylus nebo Plateosaurus. Stejně tak leyesaura od těchto zvířat odlišuje kýl na spodní straně přední části krčních obratlů 3 až 6 a na celé spodní straně obratle 7, který jej naopak přibližuje yunnanosaurovi a tekodontosaurovi.
Ke zjištění leyesaurovy fylogenetické pozice byla použita matrice z Yatese et al. (2010), doplněná i o ty nejnovější objevy na poli bazálních sauropodomorfů: adeopapposaura, seitaada, chromogisaura, ignavusaura a sarahsaura. Výsledná matrice, sestávající z 54 taxonů a 361 morfologických znaků (z nichž 36 bylo vícestavových a seřazených) byla analyzována metodou nejvyšší parsimonie, která odkryla 18 optimálních stromů. Leyesaurus na nich konzistentně zaujímal pozici sesterského taxonu vůči adeopapposaurovi v rámci kladu Massospondylidae, odvozené skupiny již poměrně blízké sauropodům. Klad (Leyesaurus + Adeopapposaurus) podpořilo celkem 5 jednoznačných synapomorfií ze všech částí kostry, testy podpory ale nevyšly nijak zvlášť dobře: hodnota bootstrapu je pouhých 49% a k rozpadu kladu by stačil pouhý jeden krok navíc. Ani skupina zahrnující leyesaura, adeopapposaura a massospondyla na tom není o moc lépe. Za zmínku stojí, že massospondylidi jsou v tomto fylogenetickém rozboru rozsáhlejší, než tomu bylo u Yatese (2007), ale nezahrnují seitaada, kterého v rámci massospondylidů vykryli Sertich & Loewen (2010). Ten má nyní blíže k sauropodům (viz kladogram níže). Vrátit ho na jeho původní pozici by ovšem vyžadovalo pouhé 4 kroky navíc, což oproti nejúspornějším stromům s 1301 kroky nepředstavuje statisticky signifikantní rozdíl. Změnila se i pozice sarahsaura a ignavusaura: ti spolu nyní formují přesvědčivý klad podpořený 9 synapomorfiemi, jehož rozbití by stálo 7 až 9 kroků v závislosti na tom, kde bychom chtěli, aby Sarahsaurus a Ignavusaurus skončili. (Pro přehled: Rowe et al. [2010] odkryli sarahsaura v závislosti na použité matrici buď jako velice bazálního, non-plateosauřího sauropodomorfa, nebo jako bazálního zástupce monofyletických prosauropodů.)
Svůj článek autoři uzavírají s tím, že nové objevy, jaké představuje Glacialisaurus, Adeopapposaurus nebo třeba právě Leyesaurus, v kombinaci s koloradisaurovým přeřazením do massospondylidů činí tento klad sauropodomorfů jedním z nejrozmanitějších, který na jižní polokouli v té době existoval; na jižní polokouli se ovšem jeho výskyt neomezoval. Další nové objevy, jako Seitaad, Ignavusaurus či Sarahsaurus zase ukazují, že mezi massopody (klad vznikající posledním společným předkem massospondylidů a sauropodů) patřila i zvířata, která nemůžeme zařadit do žádného z dosud rozeznávaných "kladů vyššího řádu", jako jsou massospondylidi, riojasauridi a anchisauři.
Fotografie (A) a interpretační kresba (B) lebky leyesaurova holotyp PVSJ 706. Tmavě šedá reprezentuje matrix, světle šedá jamky na povrchu kostí. Zkratky: (a) kost úhlová, (aoF) předočnicové okno, (aoFo) předočnicová jamka, (Apmx) vzestupný výběžek maxilly, (d) kost zubní, (f) kost čelní, (itF) spodní spánkové okno, (j) kost jařmová, (l) kost slzná, (laoFo) okraj předočnicového okna vytvářený kostí slznou, (mF) mandibulární okno, (mx) maxilla, (n) kost nosní, (O) očnice, (p) kost temenní, (pf) kost předčelní, (pm) předčelistní kost, (po) kost zaočnicová, (rug) vyvýšené zdrsnění povrchu kosti, (q) kost čtvercová, (qj) kost čtverco-jařmová, (Rmx) hřeben na vzestupném výběžku maxilly, (sa) kost nadúhlová, (sf) subnariální otvůrek. Měřítko odpovídá 1 cm. (Zdroj: Apaldetti et al. 2011: Figure 3)
Striktní konsenzus 18 nejúspornějších stromů vzešlých z analýzy updateované matrice Yatese et al. (2010) metodou nejvyšší parsimonie. Bremerovy (rozkladové) indexy vyšší než 1 jsou uvedeny nad větvemi, hodnoty bootstrapu větší než 50% pod nimi. Z toho, jak málo těchto čísílek vidíme, je patrné, jak pevná tato topologie asi je – totiž vůbec. (Zdroj: Apaldetti et al. 2011: Figure 13)
To Royo-Torres et al. (2011) popisují nový exemplář tastavinsaura, titanosauriforma, kterého popsali Canudo et al. (2008), o čemž jsem napsal na starou verzi blogu. Nová kostra, od tohoto taxonu teprve druhá, pochází ze souvrství Forcall (španělská provincie Turuel), datovaného do raného aptu, tj. do doby před zhruba 120 miliony let. Sauropod, z nějž se dochovalo několik žeber, část pánevního pletence, kost vřetenní a kompletní zadní končetina, žil v nízce položeném, přímořském prostředí. Objev vedl nejen k revizi původní tastavinsaurovy diagnózy, ale také k odhalení cedarosaura a venenosaura coby jeho nejbližších příbuzných. Výsledný klad nese již od roku 2009 jméno Laurasiformes (Royo-Torres 2009), které naznačuje jeho místo původu – vznikl zde zřejmě někdy ve svrchní juře jako součást širší titanosauriformní vývojové radiace.
Mannion et al. (2011) revidují dinheirosaura, svrchnojurského portugalského sauropoda z kladu Diplodocoidea. Krom potvrzení jeho validity na základě 3 jedinečných odvozených znaků prezentují i důkladnou fylogenetickou analýzu, v níž Dinheirosaurus vyšel jako sesterská skupina severoamerického giganta supersaura. Tato pozice je nicméně poměrně labilní a pouhé 4 kroky navíc by stačili k odsunutí dinheirosaura mezi bazální diplodokoidy, což by vysvětlilo přítomnost primitivních znaků typu nerozdvojených neurálních trnů na předkřížových obratlech. Nejbazálnějším zástupcem rebbachisauridů – skupiny bazálních diplodokoidů, mezi něž patří třeba i bizarní Nigersaurus s tlamou podobnou vysavači – se stal Amazonsaurus. Argentinský Zapalasaurus unikl z rovněž jihoamerického kladu Limaysaurinae, což poněkud komplikuje rebbachisauridí biogeografii. Jeden exemplář dříve přiřazený k dinheirosaurovi podle Manniona a spol. vykazuje silnou podobnost s jiným diplodokidem, apatosaurem, a naznačuje tak, že v portugalské svrchní juře žilo více diplodokoidů vedle sebe. Pokud by hypotéza o dinheirosaurově příbuzenství se supersaurem byla správná, šlo by o další podporu pro existenci svrchnojurského pevninského spojení mezi Evropou a Severní Amerikou, které zřejmě využily i další skupiny sauropodů: existují určité slabé indicie o evropských rebbachisauridech, které ovšem vyžadují další výzkum.
Santucci a de Arruda-Campos revidují jinou, podstatně užší skupinu: klad Aeolosaurini, odvozené titanosaury blízce příbuzné saltasauridům, jejichž vnitřní diverzita v posledních letech rapidně vzrostla: o popisu panamerikansaura (Calvo & Porfiri 2010) jsem napsal i na blogu, stejně jako o letošní revizi éolosaura (Candeiro 2011). Nyní přichází popis dalšího, v pořadí už třetího podtaxonu éolosaura, pojmenovaného jako A. maximus. Kromě éolosaurových synapomorfií disponuje i dvěma unikátními znaky, totiž dobře vyvinutým hrbolem pod kloubící plochou hemálních oblouků ("chevronů") obratlů z přední a střední části ocasu a postranním vyboulením distální části kloubícího výběžku hemálních oblouků zprostřed zadního úseku ocasní páteře. Nová diagnóza kladu Aeolosaurus nepodporuje zahrnutí gondwanatitana, které navrhovali Santucci & Bertini (2001); oddělení obou taxonů prosazoval také Candeiro (2011). Fylogenetická analýza odkryla A. maximus jako sesterský taxon k dosavadním éolosaurům (A. colhuehuapensis a A. rionegrinus). Nejbližším příbuzným výsledné skupiny je pak Gondwanatitan a mezi éolosaurininy patří ještě Rinconsaurus, Maxakalisaurus a Panamericansaurus. Santucci a de Arruda-Campos také stanovují stáří svrchních vrstev souvrství Adamantina a spodních vrstev souvrství Marília, odkud pocházejí brazilské pozůstatky éolosaurininů, a to na kampán až maastricht.
Poslední z abstraktů, o němž se rozepíšu podrobněji, se týká sauropodních migrací a stojí za něm Fricke et al. (2011). Ve severoamerickém souvrství Morrison, pocházejícím ze svrchní jury, žili sauropodi v nížinách a záplavových plošinách podél řek, které byly každoročně zasaženy obdobím sucha. Tehdy mohli obří býložravci pocítit výrazný nedostatek potravy i vody, což činí jejich hojný výskyt v morrisonské pánvi obtížně pochopitelným. Na základě analogií s dnešními velkými býložravými savci byly jako možné řešení navrženy sezónní migrace za vodou i potravou, přímé doklady ale chyběly. Fricke et al. (2011) to nyní napravují. Srovnávají hladiny kyslíkových izotopů v zubní sklovině kamarasaura s uhličitany zformovanými v různých prostředích a zaznamenávají střídavé vzestupy a poklesy, dokládající sezónní přesun do výše položených oblastí. Podle autorů tyto důkazy přispějí k porozumění úlohy, kterou každoroční migrace hrála v ekologii a evoluci sauropodů.
Jako bonus bych z dnešního seznamu vypíchl studie zabývající se velice specifickou oblastí dinosauří anatomie, např. práci Boyda a spol. o mezizubních destičkách ptakopánvých nebo Otera a spol. o hemálních obloucích sauropodů. Popsána je i celá řada nových taxonů: z těch výše nezmíněných jsou to Thescelosaurus assiniboiensis, Saurolophus morrisi, Ratchasimasaurus suranareae a Yueosaurus tiantaiensis; nemluvě o tom, že jsem záměrně vynechal popis huaxiosaura, 18,7 metrů dlouhého (!) ornitopoda, jehož popis je tak strašný, že působí trochu jako paleontologická verze Sokalovy aféry: recyklovaný abstrakt má téměř každé vědecké jméno špatně napsané a uvnitř se skrývá rekonstrukce, která jako kdyby vylezla z 19. století.
Apaldetti C, Martinez RN, Alcober OA, Pol D 2011 A new basal sauropodomorph (Dinosauria: Saurischia) from Quebrada del Barro Formation (Marayes-El Carrizal Basin), Northwestern Argentina. PLoS ONE 6(11): e26964
Argentinean basal sauropodomorphs are known by several specimens from different basins; Ischigualasto, El Tranquilo, and Mogna. The Argentinean record is diverse and includes some of the most primitive known sauropodomorphs such as Panphagia and Chromogisaurus, as well as more derived forms, including several massospondylids. Until now, the Massospondylidae were the group of basal sauropodomorphs most widely spread around Pangea with a record in almost all continents, mostly from the southern hemisphere, including the only record from Antarctica.
We describe here a new basal sauropodomorph, Leyesaurus marayensis gen. et sp. nov., from the Quebrada del Barro Formation, an Upper Triassic-Lower Jurassic unit that crops out in northwestern Argentina. The new taxon is represented by a partial articulated skeleton that includes the skull, vertebral column, scapular and pelvic girdles, and hindlimb. Leyesaurus is diagnosed by a set of unique features, such as a sharply acute angle (50 degrees) formed by the ascending process of the maxilla and the alveolar margin, a straight ascending process of the maxilla with a longitudinal ridge on its lateral surface, noticeably bulging labial side of the maxillary teeth, greatly elongated cervical vertebrae, and proximal articular surface of metatarsal III that is shelf-like and medially deflected. Phylogenetic analysis recovers Leyesaurus as a basal sauropodomorph, sister taxon of Adeopapposaurus within the Massospondylidae. Moreover, the results suggest that massospondylids achieved a higher diversity than previously thought.
Our phylogenetic results differ with respect to previous analyses by rejecting the massospondylid affinities of some taxa from the northern hemisphere (e.g., Seitaad, Sarahsaurus). As a result, the new taxon Leyesaurus, coupled with other recent discoveries, suggests that the diversity of massospondylids in the southern hemisphere was higher than in other regions of Pangea. Finally, the close affinities of Leyesaurus with the Lower Jurassic Massospondylus suggest a younger age for the Quebrada del Barro Formation than previously postulated.
Averianov A, Sues H-D 2011 Skeletal remains of Tyrannosauroidea (Dinosauria: Theropoda) from the Bissekty Formation (Upper Cretaceous: Turonian) of Uzbekistan. Cretac Res doi:10.1016/j.cretres.2011.11.009
There exists a major gap in the fossil record of tyrannosauroid theropod dinosaurs spanning the early part of the Late Cretaceous. We report on skeletal remains referable to Tyrannosauroidea indet. from the Turonian Bissekty Formation at Dzharakuduk in the central Kyzylkum Desert of Uzbekistan. Phylogenetic analysis of the hypodigm places the Bissekty tyrannosauroid as a non-tyrannosaurid tyrannosauroid more basal than the Campanian tyrannosauroids Appalachiosaurus and Bistahieversor from North America.
Boyd CA, Cleland TP, Novas F 2011 Osteogenesis, homology, and function of the intercostal plates in ornithischian dinosaurs (Tetrapoda, Sauropsida). Zoomorphol 130: 305–15
Intercostal plates are bony structures positioned lateral to the anterior dorsal ribs in some ornithischian dinosaurs. Some propose these plates are homologous, or functionally analogous, with the uncinate processes of extant avian dinosaurs that assist in breathing, while others suggest they served a defensive function. To elucidate their osteogenesis, homology, and function, a histological survey of intercostal plates from three taxa (Hypsilophodon, Talenkauen, and Thescelosaurus) was undertaken. This study reveals that osteogenesis of intercostal plates closely resembles that of secondary centers of ossification in endochondral bone, typically present in the epiphyses of mammalian long bones. In contrast, ossification of avian uncinate processes begins at a primary ossification center via the development of a bony collar around a cartilaginous model. Based on these data, intercostal plates and avian uncinate processes are likely not evolutionary homologs. Dense packets of obliquely oriented Sharpey’s fibers within the parallel-fibered bone of somatically mature intercostal plates indicate these plates were positioned medial to at least a portion of the hypaxial musculature, which does not support their use as bony armor. Rather, we propose that intercostal plates performed some biomechanical function, either assisting in breathing in a way analogous to avian uncinate processes, or working together with the sternal ribs and sternal plates of these ornithischian taxa to provide increased rigidity to the anterior portion of the ribcage.
Brown CB, Boyd CA, Russell AP 2011 A new basal ornithopod dinosaur (Frenchman Formation, Saskatchewan, Canada), and implications for late Maastrichtian ornithischian diversity in North America. Zool J Linn Soc 163(4): 1157–98
A small, articulated basal ornithopod skeleton from the Frenchman Formation (late Maastrichtian) of Saskatchewan (RSM P 1225.1), previously referred to the taxon Thescelosaurus, differs from both recognized species of this taxon (Thescelosaurus neglectus and Thescelosaurus garbanii). The differences are taxonomically informative and we recognize this specimen as the holotype of a new species, Thescelosaurus assiniboiensis sp. nov., diagnosed by the presence of two autapomorphies, and displaying plesiomorphic traits more similar to those of Parksosaurus, than to those of the other Thescelosaurus species. The Frenchman Formation also harbours an intriguing faunal assemblage in which Thescelosaurus represents one of the most abundant dinosaur taxa, and preserves a relatively high proportion of small (putatively juvenile and subadult) specimens of many dinosaur taxa. Further work that increases the faunal sample from this formation, and that permits quantitative comparisons with contemporary formations, will determine whether or not these differences are well supported, and will determine their ultimate palaeobiological significance. Identification of a third species of Thescelosaurus from the late Maastrichtian of North America suggests that this taxon was more diverse than previously recognized, and shows an increase in diversity from the Campanian through the late Maastrichtian, contrasting the trends seen in most other ornithischian clades.
Brusatte SL, Sakamoto M, Montanari S, Harcourt Smith WEH 2011 The evolution of cranial form and function in theropod dinosaurs: insights from geometric morphometrics. J Evol Biol doi:10.1111/j.1420-9101.2011.02427.x
Theropod dinosaurs, an iconic clade of fossil species including Tyrannosaurus and Velociraptor, developed a great diversity of body size, skull form and feeding habits over their 160+ million year evolutionary history. Here, we utilize geometric morphometrics to study broad patterns in theropod skull shape variation and compare the distribution of taxa in cranial morphospace (form) to both phylogeny and quantitative metrics of biting behaviour (function). We find that theropod skulls primarily differ in relative anteroposterior length and snout depth and to a lesser extent in orbit size and depth of the cheek region, and oviraptorosaurs deviate most strongly from the "typical" and ancestral theropod morphologies. Noncarnivorous taxa generally fall out in distinct regions of morphospace and exhibit greater overall disparity than carnivorous taxa, whereas large-bodied carnivores independently converge on the same region of morphospace. The distribution of taxa in morphospace is strongly correlated with phylogeny but only weakly correlated with functional biting behaviour. These results imply that phylogeny, not biting function, was the major determinant of theropod skull shape.
Buffetaut E, Gibout B, Launois I, Delacroix C 2011 The sauropod dinosaur Cetiosaurus Owen in the Bathonian (Middle Jurassic) of the Ardennes (NE France): insular, but not dwarf. Carnets Géol Letter 2011/06 (CG2011_L06)
A chevron bone from a Lower Bathonian oolitic limestone in the Ardennes (NE France) is referred to the sauropod dinosaur Cetiosaurus Owen, previously known from the Middle Jurassic of England, on the basis of its rod-like distal end. This is the first well attested occurrence of Cetiosaurus in France. The presence of Cetiosaurus remains in the Bathonian of both Oxfordshire and the Ardennes is explainable by the fact that these regions were situated on the margin of the London-Brabant Massif land area, on which sauropod populations apparently lived. Contrary to the condition observed in other sauropods found in insular environments, there is no evidence of dwarfism in Cetiosaurus from the London-Brabant Massif, probably because this emergent area was connected to the much larger Fenno-Scandian Shield.
Cabreira SF, Schultz CL, Bittencourt JS, Soares MB, Fortier DC, Silva LR, Langer MC 2011 New stem-sauropodomorph (Dinosauria, Saurischia) from the Triassic of Brazil. Naturwiss doi:10.1007/s00114-011-0858-0
Post-Triassic theropod, sauropodomorph, and ornithischian dinosaurs are readily recognized based on the set of traits that typically characterize each of these groups. On the contrary, most of the early members of those lineages lack such specializations, but share a range of generalized traits also seen in more basal dinosauromorphs. Here, we report on a new Late Triassic dinosaur from the Santa Maria Formation of Rio Grande do Sul, southern Brazil. The specimen comprises the disarticulated partial skeleton of a single individual, including most of the skull bones. Based on four phylogenetic analyses, the new dinosaur fits consistently on the sauropodomorph stem, but lacks several typical features of sauropodomorphs, showing dinosaur plesiomorphies together with some neotheropod traits. This is not an exception among basal dinosaurs, the early radiation of which is characterized by a mosaic pattern of character acquisition, resulting in the uncertain phylogenetic placement of various early members of the group.
Campione NE, Evans DC 2011 Cranial growth and variation in edmontosaurs (Dinosauria: Hadrosauridae): implications for latest Cretaceous megaherbivore diversity in North America. PLoS ONE 6(9): e25186
The well-sampled Late Cretaceous fossil record of North America remains the only high-resolution dataset for evaluating patterns of dinosaur diversity leading up to the terminal Cretaceous extinction event. Hadrosaurine hadrosaurids (Dinosauria: Ornithopoda) closely related to Edmontosaurus are among the most common megaherbivores in latest Campanian and Maastrichtian deposits of western North America. However, interpretations of edmontosaur species richness and biostratigraphy have been in constant flux for almost three decades, although the clade is generally thought to have undergone a radiation in the late Maastrichtian. We address the issue of edmontosaur diversity for the first time using rigorous morphometric analyses of virtually all known complete edmontosaur skulls. Results suggest only two valid species, Edmontosaurus regalis from the late Campanian, and E. annectens from the late Maastrichtian, with previously named taxa, including the controversial Anatotitan copei, erected on hypothesized transitional morphologies associated with ontogenetic size increase and allometric growth. A revision of North American hadrosaurid taxa suggests a decrease in both hadrosaurid diversity and disparity from the early to late Maastrichtian, a pattern likely also present in ceratopsid dinosaurs. A decline in the disparity of dominant megaherbivores in the latest Maastrichtian interval supports the hypothesis that dinosaur diversity decreased immediately preceding the end Cretaceous extinction event.
Cerda I, Paulina Carabajal A, Salgado L, Coria R, Moly J 2011 The first record of sauropod dinosaurs from Antarctica. J Vert Paleont 31, SVP Program and Abstracts Book, 86
Sauropods were one of the most widely distributed group of dinosaurs for most of the Mesozoic Era, although this clade has not been previously recorded in Antarctica. Here we report the frst record of a sauropod dinosaur from Antarctica, represented by an incomplete caudal vertebra from the Late Cretaceous of the James Ross Island (Antarctic Peninsula). The vertebra was collected from marine sediments assigned to the Gamma Member of the Santa Marta Formation (Campanian), constituted mainly by fne-grained to mid-size grained sandstones. The specimen consists of a strongly procoelous middle caudal centrum lacking the neural arch. The centrum length (excluding the posterior ball) is 170 mm and its height is 105 mm. There is no pleurocoels, and a sagittal fracture has exposed the internal bone structure, which is not pneumatized. The morphology and size of the specimen allow it to be identifed as a caudal vertebra of a derived sauropod dinosaur. The anterior position of the neural arch indicates referral to Titanosauriformes. The procoely of the middle caudal vertebra has been proposed to have a diagnostic feature of lithostrotian titanosaurs. The biogeographical history of sauropods and the interrelationships amongst titanosaurs from southern landmasses remain obscure and controversial. The specimen is notable for representing the frst Antarctic sauropod record, but also the most southern record of the clade, adding new data in the process of resolving the affnities of South American titanosaurs and the understanding of Gondwanan paleobiogeography.
Curry Rogers K, D'Emic M, Rogers R, Vickaryous M, Cagan A 2011 Sauropod dinosaur osteoderms from the Late Cretaceous of Madagascar. Nature Comms 2: 564
Osteoderms are bones embedded within the dermis, and are common to select members of most major tetrapod lineages. The largest known animals that bear osteoderms are members of Titanosauria, a diverse clade of sauropod dinosaurs. Here we report on two titanosaur osteoderms recovered from the Upper Cretaceous Maevarano Formation of Madagascar. Each osteoderm was discovered in association with a partial skeleton representing a distinct ontogenetic stage of the titanosaur Rapetosaurus krausei. Combined, these specimens provide novel insights into the arrangement and function of titanosaur osteoderms. Taphonomic data confirm that Rapetosaurus developed only limited numbers of osteoderms in its integument. The adult-sized osteoderm is the most massive integumentary skeletal element yet discovered, with an estimated volume of 9.63 litres. Uniquely, this specimen possesses an internal cavity equivalent to more than half its total volume. Large, hollow osteoderms may have functioned as mineral stores in fecund, rapidly growing titanosaurs inhabiting stressed environments.
Fiorillo AR 2011 Microwear patterns on the teeth of northern high latitude hadrosaurs with comments on microwear patterns in hadrosaurs as a function of latitude and seasonal ecological constraints. Palaeont Electro 14.3.20A
Dental microwear studies have value in qualitatively addressing patterns of food use in both extinct and extant vertebrates. This study has examined dental microwear patterns on the teeth of Campanian/Maastrichtian hadrosaurs from northern Alaska to western Texas. The primary parameters examined were the incidence of pitting and the orientation of linear features on the occlusal surfaces of the teeth. The results of the examination have shown similar patterns of tooth wear independent of geographic location. Thus it may be that hadrosaurs all along western North America were consuming food items with similar hardness.
The dominant food consumed by hadrosaurs is considered to be conifers, although it is unlikely that conifers constituted the entire diet of the high latitude forms given the constraints imposed by a highly seasonal annual cycle. Further, given the similarity of food items consumed along such a large latitudinal gradient, combined with the deciduous nature of the food items in Alaska, it seems likely that northern hadrosaurs reduced their metabolic rates during the winter months, in a manner similar to many modern terrestrial Arctic vertebrates. This reduction in metabolic rate during the winter months may have been facilitated if these animals were inertial homeotherms (i.e., of a low surface: mass ratio) or ectotherms rather than full endotherms.
Fricke HC, Hencecroth J, Hoerner ME 2011 Lowland–upland migration of sauropod dinosaurs during the Late Jurassic epoch. Nature doi:10.1038/nature10570
Sauropod dinosaurs were the largest vertebrates ever to walk the Earth, and as mega-herbivores they were important parts of terrestrial ecosystems. In the Late Jurassic-aged Morrison depositional basin of western North America, these animals occupied lowland river-floodplain settings characterized by a seasonally dry climate. Massive herbivores with high nutritional and water needs could periodically experience nutritional and water stress under these conditions, and thus the common occurrence of sauropods in this basin has remained a paradox. Energetic arguments and mammalian analogues have been used to suggest that migration allowed sauropods access to food and water resources over a wide region or during times of drought or both, but there has been no direct support for these hypotheses. Here we compare oxygen isotope ratios (δ18O) of tooth-enamel carbonate from the sauropod Camarasaurus with those of ancient soil, lake and wetland (that is, ‘authigenic’) carbonates that formed in lowland settings. We demonstrate that certain populations of these animals did in fact undertake seasonal migrations of several hundred kilometres from lowland to upland environments. This ability to describe patterns of sauropod movement will help to elucidate the role that migration played in the ecology and evolution of gigantism of these and associated dinosaurs.
Galton PM, Molnar RE 2011 An unusually large theropod dinosaur tooth from the Kirkwood Formation (Lower Cretaceous) of South Africa. N Jahrb Geol Paläont Abh doi:10.1127/0077-7749/2011/0204
The basal part of the crown is described for a very large theropod dinosaur tooth that probably came from the Kirkwood Formation (Lower Cretaceous) of Eastern Cape Province, South Africa. It originated from an animal as large, or possibly larger, than Tyrannosaurus rex, and thus probably represents a new taxon for the Kirkwood fauna and the largest theropod from that fauna. Examination of the fossil record indicates that very large theropods, approximating the size of Tyrannosaurus rex, occurred from the Callovian through the Maastrichtian. Such very large forms apparently evolved sequentially in several theropod clades.
Godefroit P, Lauters P, Van Itterbeeck J, Bolotsky YL, Bolotsky IY 2011 Recent advances on study of hadrosaurid dinosaurs in Heilongjiang (Amur) River area between China and Russia. Global Geol 2011: 3
Four main dinosaur-bearing sites have been investigated in latest Cretaceous deposits from the Amur/Heilongjiang Region: Jiayin and Wulaga in China (Yuliangze Formation), Blagoveschensk and Kundur in Russia (Udurchukan Formation). More than 90% of the bones discovered in these localities belong to hollowcrested lambeosaurine hadrosaurids: Charonosaurus jiayinensis at Jiayin, Amurosaurus riabinini at Blagoveschensk, Olorotitan arharensis at Kundur,and Sahaliyania elunchunorum at Wulaga. Flat-headed hadrosaurine hadrosaurids are much less numerous, but appear well diversified as well: Kerberosaurus manakini at Blagoveschensk, Wulagasaurus dongi at Wulaga,and a new genus at Kundur. Theropods are represented by shed teeth and isolated bones; isolated scutes and teeth discovered at Kundur are tentatively attributed to nodosaurids. Palynological studies suggest that these sites are probably synchronous with the Lancian vertebrate localities of western North America, which represent the youngest dinosaur faunas in this area. However,the latest Cretaceous dinosaur assemblages are completely different in the Amur/Heilongjiang region (lambeosaurines abundant, ceratopsids absent) and in western North America (ceratopsids abundant, lambeosaurines extremely rare or absent). This probably reflects some kind of geographical barrier between both areas by Maastrichtian time rather than strong differences in palaeoecological conditions.
There exists a major gap in the fossil record of tyrannosauroid theropod dinosaurs spanning the early part of the Late Cretaceous. We report on skeletal remains referable to Tyrannosauroidea indet. from the Turonian Bissekty Formation at Dzharakuduk in the central Kyzylkum Desert of Uzbekistan. Phylogenetic analysis of the hypodigm places the Bissekty tyrannosauroid as a non-tyrannosaurid tyrannosauroid more basal than the Campanian tyrannosauroids Appalachiosaurus and Bistahieversor from North America.
Boyd CA, Cleland TP, Novas F 2011 Osteogenesis, homology, and function of the intercostal plates in ornithischian dinosaurs (Tetrapoda, Sauropsida). Zoomorphol 130: 305–15
Intercostal plates are bony structures positioned lateral to the anterior dorsal ribs in some ornithischian dinosaurs. Some propose these plates are homologous, or functionally analogous, with the uncinate processes of extant avian dinosaurs that assist in breathing, while others suggest they served a defensive function. To elucidate their osteogenesis, homology, and function, a histological survey of intercostal plates from three taxa (Hypsilophodon, Talenkauen, and Thescelosaurus) was undertaken. This study reveals that osteogenesis of intercostal plates closely resembles that of secondary centers of ossification in endochondral bone, typically present in the epiphyses of mammalian long bones. In contrast, ossification of avian uncinate processes begins at a primary ossification center via the development of a bony collar around a cartilaginous model. Based on these data, intercostal plates and avian uncinate processes are likely not evolutionary homologs. Dense packets of obliquely oriented Sharpey’s fibers within the parallel-fibered bone of somatically mature intercostal plates indicate these plates were positioned medial to at least a portion of the hypaxial musculature, which does not support their use as bony armor. Rather, we propose that intercostal plates performed some biomechanical function, either assisting in breathing in a way analogous to avian uncinate processes, or working together with the sternal ribs and sternal plates of these ornithischian taxa to provide increased rigidity to the anterior portion of the ribcage.
Brown CB, Boyd CA, Russell AP 2011 A new basal ornithopod dinosaur (Frenchman Formation, Saskatchewan, Canada), and implications for late Maastrichtian ornithischian diversity in North America. Zool J Linn Soc 163(4): 1157–98
A small, articulated basal ornithopod skeleton from the Frenchman Formation (late Maastrichtian) of Saskatchewan (RSM P 1225.1), previously referred to the taxon Thescelosaurus, differs from both recognized species of this taxon (Thescelosaurus neglectus and Thescelosaurus garbanii). The differences are taxonomically informative and we recognize this specimen as the holotype of a new species, Thescelosaurus assiniboiensis sp. nov., diagnosed by the presence of two autapomorphies, and displaying plesiomorphic traits more similar to those of Parksosaurus, than to those of the other Thescelosaurus species. The Frenchman Formation also harbours an intriguing faunal assemblage in which Thescelosaurus represents one of the most abundant dinosaur taxa, and preserves a relatively high proportion of small (putatively juvenile and subadult) specimens of many dinosaur taxa. Further work that increases the faunal sample from this formation, and that permits quantitative comparisons with contemporary formations, will determine whether or not these differences are well supported, and will determine their ultimate palaeobiological significance. Identification of a third species of Thescelosaurus from the late Maastrichtian of North America suggests that this taxon was more diverse than previously recognized, and shows an increase in diversity from the Campanian through the late Maastrichtian, contrasting the trends seen in most other ornithischian clades.
Brusatte SL, Sakamoto M, Montanari S, Harcourt Smith WEH 2011 The evolution of cranial form and function in theropod dinosaurs: insights from geometric morphometrics. J Evol Biol doi:10.1111/j.1420-9101.2011.02427.x
Theropod dinosaurs, an iconic clade of fossil species including Tyrannosaurus and Velociraptor, developed a great diversity of body size, skull form and feeding habits over their 160+ million year evolutionary history. Here, we utilize geometric morphometrics to study broad patterns in theropod skull shape variation and compare the distribution of taxa in cranial morphospace (form) to both phylogeny and quantitative metrics of biting behaviour (function). We find that theropod skulls primarily differ in relative anteroposterior length and snout depth and to a lesser extent in orbit size and depth of the cheek region, and oviraptorosaurs deviate most strongly from the "typical" and ancestral theropod morphologies. Noncarnivorous taxa generally fall out in distinct regions of morphospace and exhibit greater overall disparity than carnivorous taxa, whereas large-bodied carnivores independently converge on the same region of morphospace. The distribution of taxa in morphospace is strongly correlated with phylogeny but only weakly correlated with functional biting behaviour. These results imply that phylogeny, not biting function, was the major determinant of theropod skull shape.
Buffetaut E, Gibout B, Launois I, Delacroix C 2011 The sauropod dinosaur Cetiosaurus Owen in the Bathonian (Middle Jurassic) of the Ardennes (NE France): insular, but not dwarf. Carnets Géol Letter 2011/06 (CG2011_L06)
A chevron bone from a Lower Bathonian oolitic limestone in the Ardennes (NE France) is referred to the sauropod dinosaur Cetiosaurus Owen, previously known from the Middle Jurassic of England, on the basis of its rod-like distal end. This is the first well attested occurrence of Cetiosaurus in France. The presence of Cetiosaurus remains in the Bathonian of both Oxfordshire and the Ardennes is explainable by the fact that these regions were situated on the margin of the London-Brabant Massif land area, on which sauropod populations apparently lived. Contrary to the condition observed in other sauropods found in insular environments, there is no evidence of dwarfism in Cetiosaurus from the London-Brabant Massif, probably because this emergent area was connected to the much larger Fenno-Scandian Shield.
Cabreira SF, Schultz CL, Bittencourt JS, Soares MB, Fortier DC, Silva LR, Langer MC 2011 New stem-sauropodomorph (Dinosauria, Saurischia) from the Triassic of Brazil. Naturwiss doi:10.1007/s00114-011-0858-0
Post-Triassic theropod, sauropodomorph, and ornithischian dinosaurs are readily recognized based on the set of traits that typically characterize each of these groups. On the contrary, most of the early members of those lineages lack such specializations, but share a range of generalized traits also seen in more basal dinosauromorphs. Here, we report on a new Late Triassic dinosaur from the Santa Maria Formation of Rio Grande do Sul, southern Brazil. The specimen comprises the disarticulated partial skeleton of a single individual, including most of the skull bones. Based on four phylogenetic analyses, the new dinosaur fits consistently on the sauropodomorph stem, but lacks several typical features of sauropodomorphs, showing dinosaur plesiomorphies together with some neotheropod traits. This is not an exception among basal dinosaurs, the early radiation of which is characterized by a mosaic pattern of character acquisition, resulting in the uncertain phylogenetic placement of various early members of the group.
Campione NE, Evans DC 2011 Cranial growth and variation in edmontosaurs (Dinosauria: Hadrosauridae): implications for latest Cretaceous megaherbivore diversity in North America. PLoS ONE 6(9): e25186
The well-sampled Late Cretaceous fossil record of North America remains the only high-resolution dataset for evaluating patterns of dinosaur diversity leading up to the terminal Cretaceous extinction event. Hadrosaurine hadrosaurids (Dinosauria: Ornithopoda) closely related to Edmontosaurus are among the most common megaherbivores in latest Campanian and Maastrichtian deposits of western North America. However, interpretations of edmontosaur species richness and biostratigraphy have been in constant flux for almost three decades, although the clade is generally thought to have undergone a radiation in the late Maastrichtian. We address the issue of edmontosaur diversity for the first time using rigorous morphometric analyses of virtually all known complete edmontosaur skulls. Results suggest only two valid species, Edmontosaurus regalis from the late Campanian, and E. annectens from the late Maastrichtian, with previously named taxa, including the controversial Anatotitan copei, erected on hypothesized transitional morphologies associated with ontogenetic size increase and allometric growth. A revision of North American hadrosaurid taxa suggests a decrease in both hadrosaurid diversity and disparity from the early to late Maastrichtian, a pattern likely also present in ceratopsid dinosaurs. A decline in the disparity of dominant megaherbivores in the latest Maastrichtian interval supports the hypothesis that dinosaur diversity decreased immediately preceding the end Cretaceous extinction event.
Cerda I, Paulina Carabajal A, Salgado L, Coria R, Moly J 2011 The first record of sauropod dinosaurs from Antarctica. J Vert Paleont 31, SVP Program and Abstracts Book, 86
Sauropods were one of the most widely distributed group of dinosaurs for most of the Mesozoic Era, although this clade has not been previously recorded in Antarctica. Here we report the frst record of a sauropod dinosaur from Antarctica, represented by an incomplete caudal vertebra from the Late Cretaceous of the James Ross Island (Antarctic Peninsula). The vertebra was collected from marine sediments assigned to the Gamma Member of the Santa Marta Formation (Campanian), constituted mainly by fne-grained to mid-size grained sandstones. The specimen consists of a strongly procoelous middle caudal centrum lacking the neural arch. The centrum length (excluding the posterior ball) is 170 mm and its height is 105 mm. There is no pleurocoels, and a sagittal fracture has exposed the internal bone structure, which is not pneumatized. The morphology and size of the specimen allow it to be identifed as a caudal vertebra of a derived sauropod dinosaur. The anterior position of the neural arch indicates referral to Titanosauriformes. The procoely of the middle caudal vertebra has been proposed to have a diagnostic feature of lithostrotian titanosaurs. The biogeographical history of sauropods and the interrelationships amongst titanosaurs from southern landmasses remain obscure and controversial. The specimen is notable for representing the frst Antarctic sauropod record, but also the most southern record of the clade, adding new data in the process of resolving the affnities of South American titanosaurs and the understanding of Gondwanan paleobiogeography.
Curry Rogers K, D'Emic M, Rogers R, Vickaryous M, Cagan A 2011 Sauropod dinosaur osteoderms from the Late Cretaceous of Madagascar. Nature Comms 2: 564
Osteoderms are bones embedded within the dermis, and are common to select members of most major tetrapod lineages. The largest known animals that bear osteoderms are members of Titanosauria, a diverse clade of sauropod dinosaurs. Here we report on two titanosaur osteoderms recovered from the Upper Cretaceous Maevarano Formation of Madagascar. Each osteoderm was discovered in association with a partial skeleton representing a distinct ontogenetic stage of the titanosaur Rapetosaurus krausei. Combined, these specimens provide novel insights into the arrangement and function of titanosaur osteoderms. Taphonomic data confirm that Rapetosaurus developed only limited numbers of osteoderms in its integument. The adult-sized osteoderm is the most massive integumentary skeletal element yet discovered, with an estimated volume of 9.63 litres. Uniquely, this specimen possesses an internal cavity equivalent to more than half its total volume. Large, hollow osteoderms may have functioned as mineral stores in fecund, rapidly growing titanosaurs inhabiting stressed environments.
Fastovsky DE, Weishampel DB, Watabe M, Barsbold R, Tsogtbaatar K, Narmandakh P 2011 A nest of Protoceratops andrewsi (Dinosauria, Ornithischia). J Paleontol 85(6): 1035–41
A remarkable specimen of the small neoceratopsian dinosaur Protoceratops andrewsi (Late Cretaceous, Mongolia) reveals the first nest of this genus, complete with fifteen juveniles. The relatively large size of the individuals and their advanced state of development suggests the possibility that Protoceratops juveniles remained and grew in their nests during at least the early stages of postnatal development. The nest further implies that parental care and sociality are phylogenetically basal behaviors in Ceratopsia. Finally, it reaffirms the conclusion that Protoceratops lived (and died) in the sandy aeolian dune fields of the central Asian craton.
Fiorillo AR 2011 Microwear patterns on the teeth of northern high latitude hadrosaurs with comments on microwear patterns in hadrosaurs as a function of latitude and seasonal ecological constraints. Palaeont Electro 14.3.20A
Dental microwear studies have value in qualitatively addressing patterns of food use in both extinct and extant vertebrates. This study has examined dental microwear patterns on the teeth of Campanian/Maastrichtian hadrosaurs from northern Alaska to western Texas. The primary parameters examined were the incidence of pitting and the orientation of linear features on the occlusal surfaces of the teeth. The results of the examination have shown similar patterns of tooth wear independent of geographic location. Thus it may be that hadrosaurs all along western North America were consuming food items with similar hardness.
The dominant food consumed by hadrosaurs is considered to be conifers, although it is unlikely that conifers constituted the entire diet of the high latitude forms given the constraints imposed by a highly seasonal annual cycle. Further, given the similarity of food items consumed along such a large latitudinal gradient, combined with the deciduous nature of the food items in Alaska, it seems likely that northern hadrosaurs reduced their metabolic rates during the winter months, in a manner similar to many modern terrestrial Arctic vertebrates. This reduction in metabolic rate during the winter months may have been facilitated if these animals were inertial homeotherms (i.e., of a low surface: mass ratio) or ectotherms rather than full endotherms.
Fricke HC, Hencecroth J, Hoerner ME 2011 Lowland–upland migration of sauropod dinosaurs during the Late Jurassic epoch. Nature doi:10.1038/nature10570
Sauropod dinosaurs were the largest vertebrates ever to walk the Earth, and as mega-herbivores they were important parts of terrestrial ecosystems. In the Late Jurassic-aged Morrison depositional basin of western North America, these animals occupied lowland river-floodplain settings characterized by a seasonally dry climate. Massive herbivores with high nutritional and water needs could periodically experience nutritional and water stress under these conditions, and thus the common occurrence of sauropods in this basin has remained a paradox. Energetic arguments and mammalian analogues have been used to suggest that migration allowed sauropods access to food and water resources over a wide region or during times of drought or both, but there has been no direct support for these hypotheses. Here we compare oxygen isotope ratios (δ18O) of tooth-enamel carbonate from the sauropod Camarasaurus with those of ancient soil, lake and wetland (that is, ‘authigenic’) carbonates that formed in lowland settings. We demonstrate that certain populations of these animals did in fact undertake seasonal migrations of several hundred kilometres from lowland to upland environments. This ability to describe patterns of sauropod movement will help to elucidate the role that migration played in the ecology and evolution of gigantism of these and associated dinosaurs.
Galton PM, Molnar RE 2011 An unusually large theropod dinosaur tooth from the Kirkwood Formation (Lower Cretaceous) of South Africa. N Jahrb Geol Paläont Abh doi:10.1127/0077-7749/2011/0204
The basal part of the crown is described for a very large theropod dinosaur tooth that probably came from the Kirkwood Formation (Lower Cretaceous) of Eastern Cape Province, South Africa. It originated from an animal as large, or possibly larger, than Tyrannosaurus rex, and thus probably represents a new taxon for the Kirkwood fauna and the largest theropod from that fauna. Examination of the fossil record indicates that very large theropods, approximating the size of Tyrannosaurus rex, occurred from the Callovian through the Maastrichtian. Such very large forms apparently evolved sequentially in several theropod clades.
Godefroit P, Lauters P, Van Itterbeeck J, Bolotsky YL, Bolotsky IY 2011 Recent advances on study of hadrosaurid dinosaurs in Heilongjiang (Amur) River area between China and Russia. Global Geol 2011: 3
Four main dinosaur-bearing sites have been investigated in latest Cretaceous deposits from the Amur/Heilongjiang Region: Jiayin and Wulaga in China (Yuliangze Formation), Blagoveschensk and Kundur in Russia (Udurchukan Formation). More than 90% of the bones discovered in these localities belong to hollowcrested lambeosaurine hadrosaurids: Charonosaurus jiayinensis at Jiayin, Amurosaurus riabinini at Blagoveschensk, Olorotitan arharensis at Kundur,and Sahaliyania elunchunorum at Wulaga. Flat-headed hadrosaurine hadrosaurids are much less numerous, but appear well diversified as well: Kerberosaurus manakini at Blagoveschensk, Wulagasaurus dongi at Wulaga,and a new genus at Kundur. Theropods are represented by shed teeth and isolated bones; isolated scutes and teeth discovered at Kundur are tentatively attributed to nodosaurids. Palynological studies suggest that these sites are probably synchronous with the Lancian vertebrate localities of western North America, which represent the youngest dinosaur faunas in this area. However,the latest Cretaceous dinosaur assemblages are completely different in the Amur/Heilongjiang region (lambeosaurines abundant, ceratopsids absent) and in western North America (ceratopsids abundant, lambeosaurines extremely rare or absent). This probably reflects some kind of geographical barrier between both areas by Maastrichtian time rather than strong differences in palaeoecological conditions.
Described herein are two large theropod tracks from the Lower Cretaceous Donghe Group in Shaojian Village, Shangluo City, Shaanxi Province. The tracks are attributed to Megalosauripus isp. The Donghe Group is contemporaneous with the Jehol Biota. Megalosauripus isp. at the Shaojian track site can be compared with the foot structure of large theropods of the Jehol Biota. Furthermore, the length of the track maker of Megalosauripus isp. is approximately 7.4 m, which suggests that large theropods occurred in central-southern Shaanxi Province in the Lower Cretaceous. The discovery of Megalosauripus isp. adds a new member to Lower Cretaceous dinosaur footprints in China, and also indicates the very probable discovery of large-sized theropod dinosaur skeletons from the Lower Cretaceous sediments of this area in the near future.
Ibiricu LM, Casal GA, Lamanna MC, Martínez RD, Harris JD, Lacovara KJ 2011 The southernmost records of Rebbachisauridae (Sauropoda: Diplodocoidea), from early Late Cretaceous deposits in central Patagonia. Cretac Res doi:10.1016/j.cretres.2011.11.003
We describe new and redescribe previously discovered sauropod dinosaur material from the Upper Cretaceous (middle Cenomanian-Coniacian) Bajo Barreal Formation of south-central Chubut Province, central Patagonia, Argentina. The remains consist of associated and isolated axial skeletal elements recovered from three separate localities, and are herein assigned to the morphologically aberrant Rebbachisauridae clade. Several of the fossils exhibit osteological characters that were previously undocumented in rebbachisaurids, enhancing our understanding of the morphological diversity of this enigmatic sauropod group. In particular, the Bajo Barreal material demonstrates the occurrence within Rebbachisauridae of bifurcate neural spines in cervical vertebrae and well-developed, presumably pneumatic fossae in caudal vertebrae; among Diplodocoidea, these distinctive morphologies had previously been recognized only in flagellicaudatans. Furthermore, the Bajo Barreal fossils constitute the southernmost known occurrences of Diplodocoidea, adding to the globally sparse Late Cretaceous record of these sauropods and augmenting our knowledge of central Patagonian terrestrial vertebrate assemblages during this interval.
Knight TK, Bingham PS, Lewis RD, Savrda CE 2011 Feathers of the Ingersoll Shale, Eutaw Formation (Upper Cretaceous), eastern Alabama: the largest collection of feathers from North American Mesozoic rocks. Palaios 26(6): 364-76
The Ingersoll shale (Santonian) is a small mudstone lens in eastern Alabama, interpreted as an abandoned tidal-channel fill that accumulated rapidly within the lower reaches of a bayhead delta. The diverse biota found in this fossil Lagerstätte includes 14 individual feather specimens, the largest collection known from the Mesozoic of North America. Occurring separately throughout nearly the entire thickness of the clay lens and with a range of sizes and morphologies, the feathers most likely represent a number of theropod species. Based on known taxa in the region, the largest specimen (16.5 cm) may be a rectrix (tail feather) from a dromaeosaurid dinosaur or from a hesperornithid. Smaller feathers may have belonged to a range of shore birds. The best-preserved specimens were found in the finest grained intervals. SEM examination reveals very well preserved microstructure consisting of carbonized rod-shaped bodies ∼1 µm in length, preserved in three dimensions and solid internally. Although identical in size and shape to modern feather-degrading bacilliform bacteria and displaying some bacteria-like features, their alignment along the axis of feather structures indicates that they are more likely the fossil remains of melanosomes, melanin bodies used for color production during life. No three-dimensional arrays or patterned differences of morphotypes have been seen thus far; almost all elements are elongate (apparently eumelanin). Inferred colors for four of the feathers, based on differences in melanosome morphologies, range from gray and brownish gray to black. Whereas the majority of feather-bearing deposits represent inland lakes, the estuarine setting adds a view of coastal feathered theropods preserved in detail by rapid deposition of fine-grained sediment.
Maidment SCR, Barrett PM 2011 The locomotor musculature of basal ornithischian dinosaurs. J Vert Paleont 31(6): 1265–91
The earliest ornithischian dinosaurs were small bipeds that possessed the derived, retroverted pubis that is synapomorphic for the clade. Their forelimbs were modified for grasping. Subsequently, ornithischians radiated into numerous body shapes and sizes. Three lineages independently evolved large size and quadrupedality, requiring profound changes to the osteology and myology of the locomotor apparatus. Using comparisons with extinct archosaurian outgroups, as well as extant birds and crocodilians, we reconstruct basal ornithischian limb musculature in order to determine the sequence of musculoskeletal changes that occurred prior to and during the early evolution of Ornithischia. The musculoskeletal anatomy of basal ornithischian forelimbs was probably more similar to that of the crown group archosaur common ancestor and crocodilians than it was to birds. Reduction or loss of the clavicle resulted in migration of the clavicular deltoid onto the proximal scapula and development of a distinct acromial process. The coracobrachialis brevis and supracoracoideus probably protracted the humerus, whereas the scapulohumeralis caudalis and deltoideus scapularis probably retracted it. The deltoideus clavicularis was likely a humeral abductor. In the hind limb, the elongate preacetabular process indicates lateral migration of important femoral protractors to the ilium from an inferred ancestral location on the dorsal vertebrae. The puboischiofemoralis externus was greatly reduced or possibly lost due to pubic retroversion. The reconstruction of basal ornithischian myology provides a baseline for determining the musculoskeletal changes associated with different locomotor modes in ornithischians, and a foundation for biomechanical studies of dinosaur locomotion.
Mannion PD, Upchurch P, Mateus O, Barnes RN, Jones MEH 2011 New information on the anatomy and systematic position of Dinheirosaurus lourinhanensis (Sauropoda: Diplodocoidea) from the Late Jurassic of Portugal, with a review of European diplodocoids. J Syst Palaeont doi:10.1080/14772019.2011.595432
Although diplodocoid sauropods from Africa and the Americas are well known, their European record remains largely neglected. Here we redescribe Dinheirosaurus lourinhanensis from the Late Jurassic of Portugal. The holotype comprises two posterior cervical vertebrae, the dorsal series and a caudal centrum. Redescription demonstrates its validity on the basis of three autapomorphies: (1) posteriorly restricted ventral keel on posterior cervical vertebrae; (2) three small subcircular fossae posterior to the lateral coel on posterior cervical neural spines; (3) accessory lamina linking the hyposphene with base of the posterior centrodiapophyseal lamina in middle-posterior dorsal vertebrae. Phylogenetic analysis places Dinheirosaurus as the sister taxon to Supersaurus, and this clade forms the sister taxon to other diplodocines. However, this position should be treated with caution as Dinheirosaurus displays several plesiomorphic features absent in other diplodocids (including unbifurcated presacral neural spines, and dorsolaterally projecting diapophyses on dorsal vertebrae) and only four additional steps are required to place Dinheirosaurus outside of Flagellicaudata. We identify Amazonsaurus as the basal-most rebbachisaurid and recover Zapalasaurus outside of the South American Limaysaurinae, suggesting the biogeographic history of rebbachisaurids is more complex than previously proposed. Review of the European diplodocoid record reveals evidence for the earliest known diplodocid, as well as additional diplodocid remains from the Late Jurassic of Spain. A Portuguese specimen, previously referred to Dinheirosaurus, displays strong similarities to Apatosaurus from the contemporaneous Morrison Formation of North America, indicating the presence of a second Late Jurassic Portuguese diplodocid taxon. Along with Dinheirosaurus, these Portuguese remains provide further evidence for a Late Jurassic palaeobiogeographic connection between Europe and North America. No dicraeosaurids are currently known from Europe, but rebbachisaurids are present in the Early Cretaceous, with weak evidence for the earliest known representative from the Late Jurassic of Spain; however, more complete material is required to recognize early members of this clade.
Miyashita T, Arbour VM, Witmer LM, Currie PJ 2011 The internal cranial morphology of an armoured dinosaur Euoplocephalus corroborated by X-ray computed tomographic reconstruction. J Anat 219(6): 661–75
Internal cranial anatomy is a challenging area to study in fossilized skulls because of small sample sizes and varied post-mortem preservational alterations. This difficulty has led to the lack of correspondence between results obtained from direct osteological observation and from more indirect reconstruction methods. This paper presents corroborating evidence from direct osteological observation and from reconstruction based on computed X-ray tomography (CT) on the internal cranial anatomy of the ankylosaurid dinosaur Euoplocephalus tutus. A remarkable specimen of Euoplocephalus preserves rarely observed internal cranial structures such as vascular impressions in the nasal cavity, olfactory turbinates and possible impressions of conchae. Comparison with fossils and CT models of other taxa and other Euoplocephalus specimens adds osteological evidence for the previously reconstructed nasal cavity in this dinosaur and revises the previously described braincase morphology. A new interpretation of the ethmoidal homology identifies a mesethmoid, sphenethmoid and ectethmoid. These ethmoidal ossifications are continuous with the mineralized walls of the nasal cavity. The location of the olfactory fenestra provides further evidence that the olfactory regions of the nasal cavity are pushed to the sides of the main airway. This implies that the function of the vascular impressions in the nasal cavity and the looping of the cavity are not related to olfaction. A byproduct of the elongate, looping airway is a dramatic increase in surface area of the nasal respiratory mucosa, which in extant species has been linked to heat and water balance. A role in vocalization as a resonating chamber is another possible function of the looping and elongation of the nasal cavity. Olfaction remains as a possible function for the enlarged olfactory region, suggesting that multiple functions account for different parts of the ankylosaurid nasal cavity that underwent substantial modification. Cranial endocasts show negligible variation within Euoplocephalus, which lends some confidence to interspecific comparisons of endocranial morphology.
Otero A, Gallina PA, Canale JI, Haluza A 2011 Sauropod haemal arches: morphotypes, new classification and phylogenetic aspects. Hist Biol doi:10.1080/08912963.2011.618269
Sauropod haemal arches are caudal bony structures that have been traditionally incorporated into two different types observed in different anatomical views: Y-shaped (anterior view) and forked (lateral view). This research proposes a classification combining information observed in anterior and lateral views. Four types of ‘Y-shaped’ and six types of ‘V-shaped’ chevrons were recognised. Complete chevron series in some eusauropods allows the comparison of topological equivalent structures along the tail and also among taxa. A basal titanosaur from Argentina exhibits mid-caudal chevron morphology in which more than one cranial and caudal process is present, arising from the distal blades as well as from the proximal rami, a condition not seen before in a sauropod dinosaur. The morphological variability seen in sauropod chevrons along the tail is in close relationship with the development and distribution of muscle. caudofemoralis longus, as seen in extant crocodiles and as previously proposed for non-avian theropods and for caudal centra and transverse processes of sauropod dinosaurs. Two new characters related to middle chevrons are proposed here, in which the transitional morphology is described.
Prieto-Márquez A, Norell MA 2011 Redescription of a nearly complete skull of Plateosaurus (Dinosauria: Sauropodomorpha) from the Late Triassic of Trossingen (Germany). Am Mus Novit 3727: 1–58
The nearly complete, disarticulated skull of AMNH FARB 6810, a specimen of the basal sauropodomorph Plateosaurus collected in 1925 from the Norian (Late Triassic) strata of the Knollenmergel beds of Trossingen (Germany), is redescribed. This study supports referral of AMNH FARB 6810 to P. erlenbergiensis on the basis of the following characters: occipital condyle above level of parasphenoid; basisphenoid with transverse, subvertical lamina extending between basipterygoid processes, with ventrally projecting median process; and peglike process projecting medially from the middle of the palatine. Furthermore, P. longiceps is regarded a junior synonym of P. erlenbergiensis because the type specimen of the latter is diagnostic (displaying the above-noted apomorphies of the braincase and palatine) and, chronologically, P. erlenbergiensis has priority over P. longiceps.
Prieto-Márquez A, Wagner JR 2011 Saurolophus morrisi, a new species of hadrosaurid dinosaur from the Late Cretaceous of the Pacific coast of North America. Acta Palaeont Pol doi:10.4202/app.2011.0049
We describe and re-evaluate the systematics of specimens from the Maastrichtian Moreno Formation of California (western USA) as a new species of Saurolophus, the only known genus of hadrosaurid dinosaur widespread in Asia and North America. Recognition of this new species adds substantially to the record of the taxonomic diversity of these animals west of the Rocky Mountains. The new species, S. morrisi, is diagnosed by the possession of a postorbital having ornamentation in form of wide oblique groove on jugal process. Placement of this new species in Saurolophus considerably expands the distribution of this genus, although this referral is arbitrary since phylogenetic analysis places the new species outside of the clade formed by S. osborni and S. angustirostris. However, recognition of a new, endemic Californian hadrosaurid, especially one so closely related to both Asian and North American species, may have implications for future studies of both the internal biogeography of Western North America, and the history of exchange with Asia.
Royo-Torres R, Alcalá L, Cobos A 2011 A new specimen of the Cretaceous sauropod Tastavinsaurus sanzi from El Castellar (Teruel, Spain), and a phylogenetic analysis of the Laurasiformes. Cretac Res doi:10.1016/j.cretres.2011.10.005
This work describes a new specimen of the sauropod Tastavinsaurus sanzi, the second of this species recovered. Found at the La Canaleta site (CT-19) at El Castellar (Teruel, Spain), this new specimen is partially articulated. The site lies at the base of the Forcall Formation (early Aptian in age), which is composed of clays and sand, suggesting the area to have been a very shallow, tidal, coastal environment before becoming deeper at the margin of the Maestrazgo Basin. The anatomical elements of T. sanzi recovered include 16 dorsal ribs, some remains of the pelvic girdle, a radius, and a complete hindlimb. The original diagnosis of T. sanzi is revised. The characters of this new specimen confirm it to be a taxon of Titanosauriformes, and allow its inclusion within the clade Laurasiformes, which currently has three taxa: Tastavinsaurus, Cedarosaurus and Venenosaurus. Laurasiformes might have its origin in the Late Jurassic of Laurasia and a radiation that occurred in the Early Cretaceous.
Santucci RM, de Arruda-Campos AC 2011 A new sauropod (Macronaria, Titanosauria) from the Adamantina Formation, Bauru Group, Upper Cretaceous of Brazil and the phylogenetic relationships of Aeolosaurini. Zootaxa 3085: 1–33
Remains of a new titanosaur, Aeolosaurus maximus sp. nov., from the Adamantina Formation (Upper Cretaceous), Bauru Group, São Paulo State of Brazil are described. The new species is represented by a single partially articulated skeleton and is characterized by having a well-developed posterior protuberance below the articular area on the anterior and middle haemal arches and a lateral bulge on the distal portion of the articular process of the mid-posterior haemal arches. It shares with other Aeolosaurus species the presence of prezygapophyses curved downward on anterior caudal vertebrae and haemal arches with double articular facets set in a concave posterodorsal surface. These two characteristics are interpreted here as synapomorphies for the genus Aeolosaurus. The new diagnosis for the genus Aeolosaurus does not support the inclusion of Gondwanatitan within Aeolosaurus as previously proposed by some authors. The phylogenetic analysis recovered the two Aeolosaurus from Argentina as sister groups with A. maximus and Gondwanatitan as progressively more basal taxa (Gondwanatitan (A. maximus (A. rionegrinus, A. colhuehuapensis))). Additionally, according to the results of the phylogenetic analysis performed in this work, the taxa Panamericansaurus, Rinconsaurus, and Maxakalisaurus are also nested within Aeolosaurini, being more basal than Aeolosaurus and Gondwanatitan. On the basis of the stratigraphical range of the Aeolosaurus occurrences in Argentina and the age proposals based on microfossils for the Bauru Group, it is assumed a Campanian–Maastrichtian age for the top of the Adamantina Formation for the Monte Alto region in São Paulo State and the bottom of the Marília Formation in Peirópolis, Minas Gerais State—the places where Aeolosaurus remains have been reported in Brazil.
Shibata M, Jintasakul P, Azuma Y 2011 A new iguanodontian dinosaur from the Lower Cretaceous Khok Kruat Formation, Nakhon Ratchasima in Northeastern Thailand. Acta Geol Sin–Engl 85(5): 969–76
Here we report a new iguanodontian dentary found from the Lower Cretaceous Khok Kruat Formation, Nakhon Ratchasima, northeast Thailand. A unique character, which is an elongated and flat shape of the dentary ramus, makes it possible to assign the specimen to the new genus of non-hadrosaurid iguanodontian, Ratchasimasaurus suranareae gen. et sp. nov. R. suranareae shows both primitive and derived characters, such as a caudally inclined coronoid process and alveolar trough with a primitive crown impression, and a derived buccal shelf between tooth row and coronoid process. The discovery of a new iguanodontian from the Indochina Terrene, considering that the previously reported “Probactrosaurus-like” iguanodontian, points out a great diversity of this group in the late Early Cretaceous in Thailand, and corresponds to the Asian iguanodontian diversity at that time.
Thulborn RA 2011 Lark Quarry revisited: a critique of methods used to identify a large dinosaurian track-maker in the Winton Formation (Albian–Cenomanian), western Queensland, Australia. Cretac Res doi:10.1016/j.cretres.2011.11.006
A remarkable assemblage of dinosaur tracks in the Winton Formation (Albian–Cenomanian) at Lark Quarry, a site in western Queensland, Australia, has long been regarded as evidence of a dinosaurian stampede. However, one recently published study has claimed that existing interpretation of Lark Quarry is incorrect because the largest track-maker at the site was misidentified and could not have played a pivotal role in precipitating a stampede. That recent study has claimed that the largest track-maker was actually an ornithopod (bipedal plant-eating dinosaur) similar or identical to Muttaburrasaurus and not, as originally supposed, a theropod (predaceous dinosaur) resembling Allosaurus. Those iconoclastic claims are examined here and are shown to be groundless: they are based partly on misconceptions and partly on fabricated data which has been assessed uncritically using quantitative measures of questionable significance. Such ill-founded claims do not reveal any substantial flaw in the existing interpretation of the Lark Quarry dinosaur tracks.
Wang Q, Zhao Z-K, Wang X-l, Jiang Y-G 2011 New ootypes of dinosaur eggs from the Late Cretaceous in Tiantai Basin, Zhejiang Province, China. Vert PalAs 49(4): 446–9
In the past ten years, a number of dinosaur eggs were found in the Tiantai Basin in Zhejiang Province, and some oospecies were reported by Fang et al. (2000, 2003), Jin et al. (2007) and Qian et al. (2008). In 2010, we described and revised 12 oogenera and 15 oospecies belonging to seven oofamilies in this basin (Wang, 2010), and some new types were reported (Wang et al., 2010a, b, Zhang, (2010). At the same time, we comprehensively surveyed localities and horizons of the dinosaur eggs and compared the dinosaur egg faunas in China (Wang et al., in press). Here we report a few more new ootypes of dinosaur eggs from the Tiantai Basin.
Xing L-D, Harris JD, Gierliński GD 2011 Therangospodus and Megalosauripus track assemblage from the Upper Jurassic-Lower Cretaceous Tuchengzi Formation of Chicheng County, Hebei Province, China and their paleoecological implications. Vert PalAs 49(4): 423–34
One hundred sixty-three footprints that pertain in Therangospodus have been found in the Tuchengzi Formation at the Luofenggou track stie in Chincheng County, Hebei Province, China. Five swim tracks were subsequently made by the same track makers after water submerged the region. In addition to the Therangospodus tracks, one exceptionally large theropod track and one possible trail trace are referred to Megalosauripus isp. Theropod tracks of the grallatorid morphotype predominate at this site and six other known Tuchengzi Formation track sites; grallatorid tracks at each of these sites are dominated by individual specimens in particular size ranges. If the tracks were made by the same species of track maker, the variation in dominant track size among sites suggests that cohabiting groups were composed mainly of members of a single age class, ethologically similar to some extant lizards and Alligator. If the tracks were instead made by different species, their size distribution (favoring smaller species) suggests that species of different sizes may have preferred discrete territories or specifically avoided close contact with other (particularly larger) species, ethologically similar to modern carnivorous mammals.
Zheng W-J, Jin X-S, Shibata M, Azuma Y, Yu F-M 2011 A new ornithischian dinosaur from the Cretaceous Liangtoutang Formation of Tiantai, Zhejiang Province, China. Cretac Res doi:10.1016/j.cretres.2011.11.001
A new ornithischian dinosaur, Yueosaurus tiantaiensis gen. et sp. nov., is erected based on a partial postcranial skeleton from the Liangtoutang Formation (Aptian–Cenomanian) of Zhejiang Province, China. It differs from other ornithischians in possessing the following unique combination of characters: prominent and slightly ventrally directed cervical parapophyses; anteroposteriorly narrow neural spines on caudal vertebrae; scapula with a ventroscapular groove, supraglenoidal buttress, supraglenoid fossa, and a strong anteroventral expansion of the scapular blade. Yueosaurus represents the first basal ornithopod taxon from southeastern China. It expands our understanding of the Cretaceous dinosaurian fauna of Zhejiang Province.
Zdroje:
Ibiricu LM, Casal GA, Lamanna MC, Martínez RD, Harris JD, Lacovara KJ 2011 The southernmost records of Rebbachisauridae (Sauropoda: Diplodocoidea), from early Late Cretaceous deposits in central Patagonia. Cretac Res doi:10.1016/j.cretres.2011.11.003
We describe new and redescribe previously discovered sauropod dinosaur material from the Upper Cretaceous (middle Cenomanian-Coniacian) Bajo Barreal Formation of south-central Chubut Province, central Patagonia, Argentina. The remains consist of associated and isolated axial skeletal elements recovered from three separate localities, and are herein assigned to the morphologically aberrant Rebbachisauridae clade. Several of the fossils exhibit osteological characters that were previously undocumented in rebbachisaurids, enhancing our understanding of the morphological diversity of this enigmatic sauropod group. In particular, the Bajo Barreal material demonstrates the occurrence within Rebbachisauridae of bifurcate neural spines in cervical vertebrae and well-developed, presumably pneumatic fossae in caudal vertebrae; among Diplodocoidea, these distinctive morphologies had previously been recognized only in flagellicaudatans. Furthermore, the Bajo Barreal fossils constitute the southernmost known occurrences of Diplodocoidea, adding to the globally sparse Late Cretaceous record of these sauropods and augmenting our knowledge of central Patagonian terrestrial vertebrate assemblages during this interval.
Knight TK, Bingham PS, Lewis RD, Savrda CE 2011 Feathers of the Ingersoll Shale, Eutaw Formation (Upper Cretaceous), eastern Alabama: the largest collection of feathers from North American Mesozoic rocks. Palaios 26(6): 364-76
The Ingersoll shale (Santonian) is a small mudstone lens in eastern Alabama, interpreted as an abandoned tidal-channel fill that accumulated rapidly within the lower reaches of a bayhead delta. The diverse biota found in this fossil Lagerstätte includes 14 individual feather specimens, the largest collection known from the Mesozoic of North America. Occurring separately throughout nearly the entire thickness of the clay lens and with a range of sizes and morphologies, the feathers most likely represent a number of theropod species. Based on known taxa in the region, the largest specimen (16.5 cm) may be a rectrix (tail feather) from a dromaeosaurid dinosaur or from a hesperornithid. Smaller feathers may have belonged to a range of shore birds. The best-preserved specimens were found in the finest grained intervals. SEM examination reveals very well preserved microstructure consisting of carbonized rod-shaped bodies ∼1 µm in length, preserved in three dimensions and solid internally. Although identical in size and shape to modern feather-degrading bacilliform bacteria and displaying some bacteria-like features, their alignment along the axis of feather structures indicates that they are more likely the fossil remains of melanosomes, melanin bodies used for color production during life. No three-dimensional arrays or patterned differences of morphotypes have been seen thus far; almost all elements are elongate (apparently eumelanin). Inferred colors for four of the feathers, based on differences in melanosome morphologies, range from gray and brownish gray to black. Whereas the majority of feather-bearing deposits represent inland lakes, the estuarine setting adds a view of coastal feathered theropods preserved in detail by rapid deposition of fine-grained sediment.
Maidment SCR, Barrett PM 2011 The locomotor musculature of basal ornithischian dinosaurs. J Vert Paleont 31(6): 1265–91
The earliest ornithischian dinosaurs were small bipeds that possessed the derived, retroverted pubis that is synapomorphic for the clade. Their forelimbs were modified for grasping. Subsequently, ornithischians radiated into numerous body shapes and sizes. Three lineages independently evolved large size and quadrupedality, requiring profound changes to the osteology and myology of the locomotor apparatus. Using comparisons with extinct archosaurian outgroups, as well as extant birds and crocodilians, we reconstruct basal ornithischian limb musculature in order to determine the sequence of musculoskeletal changes that occurred prior to and during the early evolution of Ornithischia. The musculoskeletal anatomy of basal ornithischian forelimbs was probably more similar to that of the crown group archosaur common ancestor and crocodilians than it was to birds. Reduction or loss of the clavicle resulted in migration of the clavicular deltoid onto the proximal scapula and development of a distinct acromial process. The coracobrachialis brevis and supracoracoideus probably protracted the humerus, whereas the scapulohumeralis caudalis and deltoideus scapularis probably retracted it. The deltoideus clavicularis was likely a humeral abductor. In the hind limb, the elongate preacetabular process indicates lateral migration of important femoral protractors to the ilium from an inferred ancestral location on the dorsal vertebrae. The puboischiofemoralis externus was greatly reduced or possibly lost due to pubic retroversion. The reconstruction of basal ornithischian myology provides a baseline for determining the musculoskeletal changes associated with different locomotor modes in ornithischians, and a foundation for biomechanical studies of dinosaur locomotion.
Mannion PD, Upchurch P, Mateus O, Barnes RN, Jones MEH 2011 New information on the anatomy and systematic position of Dinheirosaurus lourinhanensis (Sauropoda: Diplodocoidea) from the Late Jurassic of Portugal, with a review of European diplodocoids. J Syst Palaeont doi:10.1080/14772019.2011.595432
Although diplodocoid sauropods from Africa and the Americas are well known, their European record remains largely neglected. Here we redescribe Dinheirosaurus lourinhanensis from the Late Jurassic of Portugal. The holotype comprises two posterior cervical vertebrae, the dorsal series and a caudal centrum. Redescription demonstrates its validity on the basis of three autapomorphies: (1) posteriorly restricted ventral keel on posterior cervical vertebrae; (2) three small subcircular fossae posterior to the lateral coel on posterior cervical neural spines; (3) accessory lamina linking the hyposphene with base of the posterior centrodiapophyseal lamina in middle-posterior dorsal vertebrae. Phylogenetic analysis places Dinheirosaurus as the sister taxon to Supersaurus, and this clade forms the sister taxon to other diplodocines. However, this position should be treated with caution as Dinheirosaurus displays several plesiomorphic features absent in other diplodocids (including unbifurcated presacral neural spines, and dorsolaterally projecting diapophyses on dorsal vertebrae) and only four additional steps are required to place Dinheirosaurus outside of Flagellicaudata. We identify Amazonsaurus as the basal-most rebbachisaurid and recover Zapalasaurus outside of the South American Limaysaurinae, suggesting the biogeographic history of rebbachisaurids is more complex than previously proposed. Review of the European diplodocoid record reveals evidence for the earliest known diplodocid, as well as additional diplodocid remains from the Late Jurassic of Spain. A Portuguese specimen, previously referred to Dinheirosaurus, displays strong similarities to Apatosaurus from the contemporaneous Morrison Formation of North America, indicating the presence of a second Late Jurassic Portuguese diplodocid taxon. Along with Dinheirosaurus, these Portuguese remains provide further evidence for a Late Jurassic palaeobiogeographic connection between Europe and North America. No dicraeosaurids are currently known from Europe, but rebbachisaurids are present in the Early Cretaceous, with weak evidence for the earliest known representative from the Late Jurassic of Spain; however, more complete material is required to recognize early members of this clade.
Miyashita T, Arbour VM, Witmer LM, Currie PJ 2011 The internal cranial morphology of an armoured dinosaur Euoplocephalus corroborated by X-ray computed tomographic reconstruction. J Anat 219(6): 661–75
Internal cranial anatomy is a challenging area to study in fossilized skulls because of small sample sizes and varied post-mortem preservational alterations. This difficulty has led to the lack of correspondence between results obtained from direct osteological observation and from more indirect reconstruction methods. This paper presents corroborating evidence from direct osteological observation and from reconstruction based on computed X-ray tomography (CT) on the internal cranial anatomy of the ankylosaurid dinosaur Euoplocephalus tutus. A remarkable specimen of Euoplocephalus preserves rarely observed internal cranial structures such as vascular impressions in the nasal cavity, olfactory turbinates and possible impressions of conchae. Comparison with fossils and CT models of other taxa and other Euoplocephalus specimens adds osteological evidence for the previously reconstructed nasal cavity in this dinosaur and revises the previously described braincase morphology. A new interpretation of the ethmoidal homology identifies a mesethmoid, sphenethmoid and ectethmoid. These ethmoidal ossifications are continuous with the mineralized walls of the nasal cavity. The location of the olfactory fenestra provides further evidence that the olfactory regions of the nasal cavity are pushed to the sides of the main airway. This implies that the function of the vascular impressions in the nasal cavity and the looping of the cavity are not related to olfaction. A byproduct of the elongate, looping airway is a dramatic increase in surface area of the nasal respiratory mucosa, which in extant species has been linked to heat and water balance. A role in vocalization as a resonating chamber is another possible function of the looping and elongation of the nasal cavity. Olfaction remains as a possible function for the enlarged olfactory region, suggesting that multiple functions account for different parts of the ankylosaurid nasal cavity that underwent substantial modification. Cranial endocasts show negligible variation within Euoplocephalus, which lends some confidence to interspecific comparisons of endocranial morphology.
Otero A, Gallina PA, Canale JI, Haluza A 2011 Sauropod haemal arches: morphotypes, new classification and phylogenetic aspects. Hist Biol doi:10.1080/08912963.2011.618269
Sauropod haemal arches are caudal bony structures that have been traditionally incorporated into two different types observed in different anatomical views: Y-shaped (anterior view) and forked (lateral view). This research proposes a classification combining information observed in anterior and lateral views. Four types of ‘Y-shaped’ and six types of ‘V-shaped’ chevrons were recognised. Complete chevron series in some eusauropods allows the comparison of topological equivalent structures along the tail and also among taxa. A basal titanosaur from Argentina exhibits mid-caudal chevron morphology in which more than one cranial and caudal process is present, arising from the distal blades as well as from the proximal rami, a condition not seen before in a sauropod dinosaur. The morphological variability seen in sauropod chevrons along the tail is in close relationship with the development and distribution of muscle. caudofemoralis longus, as seen in extant crocodiles and as previously proposed for non-avian theropods and for caudal centra and transverse processes of sauropod dinosaurs. Two new characters related to middle chevrons are proposed here, in which the transitional morphology is described.
Prieto-Márquez A, Norell MA 2011 Redescription of a nearly complete skull of Plateosaurus (Dinosauria: Sauropodomorpha) from the Late Triassic of Trossingen (Germany). Am Mus Novit 3727: 1–58
The nearly complete, disarticulated skull of AMNH FARB 6810, a specimen of the basal sauropodomorph Plateosaurus collected in 1925 from the Norian (Late Triassic) strata of the Knollenmergel beds of Trossingen (Germany), is redescribed. This study supports referral of AMNH FARB 6810 to P. erlenbergiensis on the basis of the following characters: occipital condyle above level of parasphenoid; basisphenoid with transverse, subvertical lamina extending between basipterygoid processes, with ventrally projecting median process; and peglike process projecting medially from the middle of the palatine. Furthermore, P. longiceps is regarded a junior synonym of P. erlenbergiensis because the type specimen of the latter is diagnostic (displaying the above-noted apomorphies of the braincase and palatine) and, chronologically, P. erlenbergiensis has priority over P. longiceps.
Prieto-Márquez A, Wagner JR 2011 Saurolophus morrisi, a new species of hadrosaurid dinosaur from the Late Cretaceous of the Pacific coast of North America. Acta Palaeont Pol doi:10.4202/app.2011.0049
We describe and re-evaluate the systematics of specimens from the Maastrichtian Moreno Formation of California (western USA) as a new species of Saurolophus, the only known genus of hadrosaurid dinosaur widespread in Asia and North America. Recognition of this new species adds substantially to the record of the taxonomic diversity of these animals west of the Rocky Mountains. The new species, S. morrisi, is diagnosed by the possession of a postorbital having ornamentation in form of wide oblique groove on jugal process. Placement of this new species in Saurolophus considerably expands the distribution of this genus, although this referral is arbitrary since phylogenetic analysis places the new species outside of the clade formed by S. osborni and S. angustirostris. However, recognition of a new, endemic Californian hadrosaurid, especially one so closely related to both Asian and North American species, may have implications for future studies of both the internal biogeography of Western North America, and the history of exchange with Asia.
Royo-Torres R, Alcalá L, Cobos A 2011 A new specimen of the Cretaceous sauropod Tastavinsaurus sanzi from El Castellar (Teruel, Spain), and a phylogenetic analysis of the Laurasiformes. Cretac Res doi:10.1016/j.cretres.2011.10.005
This work describes a new specimen of the sauropod Tastavinsaurus sanzi, the second of this species recovered. Found at the La Canaleta site (CT-19) at El Castellar (Teruel, Spain), this new specimen is partially articulated. The site lies at the base of the Forcall Formation (early Aptian in age), which is composed of clays and sand, suggesting the area to have been a very shallow, tidal, coastal environment before becoming deeper at the margin of the Maestrazgo Basin. The anatomical elements of T. sanzi recovered include 16 dorsal ribs, some remains of the pelvic girdle, a radius, and a complete hindlimb. The original diagnosis of T. sanzi is revised. The characters of this new specimen confirm it to be a taxon of Titanosauriformes, and allow its inclusion within the clade Laurasiformes, which currently has three taxa: Tastavinsaurus, Cedarosaurus and Venenosaurus. Laurasiformes might have its origin in the Late Jurassic of Laurasia and a radiation that occurred in the Early Cretaceous.
Santucci RM, de Arruda-Campos AC 2011 A new sauropod (Macronaria, Titanosauria) from the Adamantina Formation, Bauru Group, Upper Cretaceous of Brazil and the phylogenetic relationships of Aeolosaurini. Zootaxa 3085: 1–33
Remains of a new titanosaur, Aeolosaurus maximus sp. nov., from the Adamantina Formation (Upper Cretaceous), Bauru Group, São Paulo State of Brazil are described. The new species is represented by a single partially articulated skeleton and is characterized by having a well-developed posterior protuberance below the articular area on the anterior and middle haemal arches and a lateral bulge on the distal portion of the articular process of the mid-posterior haemal arches. It shares with other Aeolosaurus species the presence of prezygapophyses curved downward on anterior caudal vertebrae and haemal arches with double articular facets set in a concave posterodorsal surface. These two characteristics are interpreted here as synapomorphies for the genus Aeolosaurus. The new diagnosis for the genus Aeolosaurus does not support the inclusion of Gondwanatitan within Aeolosaurus as previously proposed by some authors. The phylogenetic analysis recovered the two Aeolosaurus from Argentina as sister groups with A. maximus and Gondwanatitan as progressively more basal taxa (Gondwanatitan (A. maximus (A. rionegrinus, A. colhuehuapensis))). Additionally, according to the results of the phylogenetic analysis performed in this work, the taxa Panamericansaurus, Rinconsaurus, and Maxakalisaurus are also nested within Aeolosaurini, being more basal than Aeolosaurus and Gondwanatitan. On the basis of the stratigraphical range of the Aeolosaurus occurrences in Argentina and the age proposals based on microfossils for the Bauru Group, it is assumed a Campanian–Maastrichtian age for the top of the Adamantina Formation for the Monte Alto region in São Paulo State and the bottom of the Marília Formation in Peirópolis, Minas Gerais State—the places where Aeolosaurus remains have been reported in Brazil.
Shibata M, Jintasakul P, Azuma Y 2011 A new iguanodontian dinosaur from the Lower Cretaceous Khok Kruat Formation, Nakhon Ratchasima in Northeastern Thailand. Acta Geol Sin–Engl 85(5): 969–76
Here we report a new iguanodontian dentary found from the Lower Cretaceous Khok Kruat Formation, Nakhon Ratchasima, northeast Thailand. A unique character, which is an elongated and flat shape of the dentary ramus, makes it possible to assign the specimen to the new genus of non-hadrosaurid iguanodontian, Ratchasimasaurus suranareae gen. et sp. nov. R. suranareae shows both primitive and derived characters, such as a caudally inclined coronoid process and alveolar trough with a primitive crown impression, and a derived buccal shelf between tooth row and coronoid process. The discovery of a new iguanodontian from the Indochina Terrene, considering that the previously reported “Probactrosaurus-like” iguanodontian, points out a great diversity of this group in the late Early Cretaceous in Thailand, and corresponds to the Asian iguanodontian diversity at that time.
Thulborn RA 2011 Lark Quarry revisited: a critique of methods used to identify a large dinosaurian track-maker in the Winton Formation (Albian–Cenomanian), western Queensland, Australia. Cretac Res doi:10.1016/j.cretres.2011.11.006
A remarkable assemblage of dinosaur tracks in the Winton Formation (Albian–Cenomanian) at Lark Quarry, a site in western Queensland, Australia, has long been regarded as evidence of a dinosaurian stampede. However, one recently published study has claimed that existing interpretation of Lark Quarry is incorrect because the largest track-maker at the site was misidentified and could not have played a pivotal role in precipitating a stampede. That recent study has claimed that the largest track-maker was actually an ornithopod (bipedal plant-eating dinosaur) similar or identical to Muttaburrasaurus and not, as originally supposed, a theropod (predaceous dinosaur) resembling Allosaurus. Those iconoclastic claims are examined here and are shown to be groundless: they are based partly on misconceptions and partly on fabricated data which has been assessed uncritically using quantitative measures of questionable significance. Such ill-founded claims do not reveal any substantial flaw in the existing interpretation of the Lark Quarry dinosaur tracks.
Wang Q, Zhao Z-K, Wang X-l, Jiang Y-G 2011 New ootypes of dinosaur eggs from the Late Cretaceous in Tiantai Basin, Zhejiang Province, China. Vert PalAs 49(4): 446–9
In the past ten years, a number of dinosaur eggs were found in the Tiantai Basin in Zhejiang Province, and some oospecies were reported by Fang et al. (2000, 2003), Jin et al. (2007) and Qian et al. (2008). In 2010, we described and revised 12 oogenera and 15 oospecies belonging to seven oofamilies in this basin (Wang, 2010), and some new types were reported (Wang et al., 2010a, b, Zhang, (2010). At the same time, we comprehensively surveyed localities and horizons of the dinosaur eggs and compared the dinosaur egg faunas in China (Wang et al., in press). Here we report a few more new ootypes of dinosaur eggs from the Tiantai Basin.
Xing L-D, Harris JD, Gierliński GD 2011 Therangospodus and Megalosauripus track assemblage from the Upper Jurassic-Lower Cretaceous Tuchengzi Formation of Chicheng County, Hebei Province, China and their paleoecological implications. Vert PalAs 49(4): 423–34
One hundred sixty-three footprints that pertain in Therangospodus have been found in the Tuchengzi Formation at the Luofenggou track stie in Chincheng County, Hebei Province, China. Five swim tracks were subsequently made by the same track makers after water submerged the region. In addition to the Therangospodus tracks, one exceptionally large theropod track and one possible trail trace are referred to Megalosauripus isp. Theropod tracks of the grallatorid morphotype predominate at this site and six other known Tuchengzi Formation track sites; grallatorid tracks at each of these sites are dominated by individual specimens in particular size ranges. If the tracks were made by the same species of track maker, the variation in dominant track size among sites suggests that cohabiting groups were composed mainly of members of a single age class, ethologically similar to some extant lizards and Alligator. If the tracks were instead made by different species, their size distribution (favoring smaller species) suggests that species of different sizes may have preferred discrete territories or specifically avoided close contact with other (particularly larger) species, ethologically similar to modern carnivorous mammals.
Zheng W-J, Jin X-S, Shibata M, Azuma Y, Yu F-M 2011 A new ornithischian dinosaur from the Cretaceous Liangtoutang Formation of Tiantai, Zhejiang Province, China. Cretac Res doi:10.1016/j.cretres.2011.11.001
A new ornithischian dinosaur, Yueosaurus tiantaiensis gen. et sp. nov., is erected based on a partial postcranial skeleton from the Liangtoutang Formation (Aptian–Cenomanian) of Zhejiang Province, China. It differs from other ornithischians in possessing the following unique combination of characters: prominent and slightly ventrally directed cervical parapophyses; anteroposteriorly narrow neural spines on caudal vertebrae; scapula with a ventroscapular groove, supraglenoidal buttress, supraglenoid fossa, and a strong anteroventral expansion of the scapular blade. Yueosaurus represents the first basal ornithopod taxon from southeastern China. It expands our understanding of the Cretaceous dinosaurian fauna of Zhejiang Province.
Zdroje:
- Calvo JO, Porfiri JD 2010 Panamericansaurus schroederi gen. nov. sp. nov. Un nuevo Sauropoda (Titanosauridae-Aeolosaurini) de la Provincia del Neuquén, Cretácico Superior de Patagonia, Argentina. Brazil Geogr J 1: 100–15
- Candeiro CRA 2011 Record of the genus Aeolosaurus (Sauropoda, Titanosauria) in the Late Cretaceous of South America: paleogeographic implications. Estudios Geol 66(2): 243–53
- Canudo JI, Royo-Torres R, Cuenca-Bescós G 2008 A new sauropod: Tastavinsaurus sanzi gen. et sp. nov. from the Early Cretaceous (Aptian) of Spain. J Vert Paleont 28(3): 712–31
- Ezcurra MD 2010 A new early dinosaur (Saurischia: Sauropodomorpha) from the Late Triassic of Argentina: a reassessment of dinosaur origin and phylogeny. J Syst Palaeont 8(3): 371–425
- Langer MC 2003 The pelvic and hind limb anatomy of the stem-sauropodomorph Saturnalia tupiniquim (Late Triassic, Brazil). PaleoBios 23(2): 1–30
- Martinez RN, Alcober OA 2009 A basal sauropodomorph (Dinosauria: Saurischia) from the Ischigualasto Formation (Triassic, Carnian) and the earlye volution of Sauropodomorpha. PLoS ONE 4(2): e4397
- Martinez RN, Sereno PC, Alcober OA, Colombi CE, Renne PR, Montañez IP, Currie BS 2011 A basal dinosaur from the dawn of the dinosaur era in southwestern Pangaea. Science 331(6014): 206–10
- Nesbitt SJ, Sidor CA, Irmis RB, Angielczyk KD, Smith RMH, Tsuji LA 2010 Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira. Nature 464(7285): 95–8
- Rowe TB, Sues HD, Reisz RR 2010 Dispersal and diversity in the earliest North American sauropodomorph dinosaurs, with a description of a new taxon. Proc R Soc B 278(1708): 1044–53
- Royo-Torres R 2009 Los dinosaurios saurópodos en la Península Ibérica. 139–66 in Colectivo Arqueológico-Paleontológico de Salas, ed. Actas de las IV Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno. Burgos: Salas de los Infantes
- Santucci RM, Bertini RJ 2001 Distribuição paleogeográfica e biocronológica dos titanossauros (Saurischia: Sauropoda) do Grupo Bauru, Cretáceo Superior do Brasil. Rev Brasil Geociênc 31(3): 307–14
- Sertich JJW, Loewen MA 2010 A new basal sauropodomorph dinosaur from the Lower Jurassic Navajo Sandstone of southern Utah. PLoS ONE 5(3): e9789
- Yates AM 2007 Solving a dinosaurian puzzle: the identity of Aliwalia rex Galton. Hist Biol 19: 93–123
- Yates AM, Bonnan MF, Neveling J, Chinsamy A, Blackbeard MG 2010 A new transitional sauropodomorph dinosaur from the Early Jurassic of South Africa and the evolution of sauropod feeding and quadrupedalism. Proc R Soc B 277(1682): 787–94
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