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New Discoveries of Fossil Reptiles
Closing the gaps


Theropod/Sauropod split documented at 230 million years ago in Argentina; January 2011



 

Eodromaeus murphi illustrations courtesy Science

A Basal Dinosaur from the Dawn of the Dinosaur Era in Southwestern Pangaea

Ricardo N. Martinez, Paul C. Sereno, Oscar A. Alcober, Carina E. Colombi, Paul R. Renne, Isabel P. Monta�ez, Brian S. Currie Science, Volume 331, 14 January 2011


Abstract  Upper Triassic rocks in northwestern Argentina preserve the most complete record of dinosaurs before their rise to dominance in the Early Jurassic. Here, we describe a previously unidentified basal theropod, reassess its contemporary Eoraptor as a basal sauropodomorph, divide the faunal record of the Ischigualasto Formation with biozones, and bracket the formation with 40Ar/39Ar ages. Some 230 million years ago in the Late Triassic (mid Carnian), the earliest dinosaurs were the dominant terrestrial carnivores and small herbivores in southwestern Pangaea. The extinction of nondinosaurian herbivores is sequential and is not linked to an increase in dinosaurian diversity, which weakens the predominant scenario for dinosaurian ascendancy as opportunistic replacement.

Source: Science.



 New 164 million year old turtle documents transition
 from land to water.
 November 2008



 

Eileanchelys waldmani illustration courtesy BBC

A new stem turtle from the Middle Jurassic of Scotland: new insights into the evolution and palaeoecology of basal turtles

J�r�my Anquetin, Paul M. Barrett, Marc E.H. Jones, Scott Moore-Fay, Susan E. Evans, Proceedings of the Royal Society B, doi:10.1098/rspb.2008.1429.


Abstract  The discovery of a new stem turtle from the Middle Jurassic (Bathonian) deposits of the Isle of Skye, Scotland, sheds new light on the early evolutionary history of Testudinata. Eileanchelys waldmani gen. et sp. nov. is known from cranial and postcranial material of several individuals and represents the most complete Middle Jurassic turtle described to date, bridging the morphological gap between basal turtles from the Late Triassic�Early Jurassic and crown-group turtles that diversify during the Late Jurassic. A phylogenetic analysis places the new taxon within the stem group of Testudines (crown-group turtles) and suggests a sister-group relationship between E. waldmani and Heckerochelys romani from the Middle Jurassic of Russia. Moreover, E. waldmani also demonstrates that stem turtles were ecologically diverse, as it may represent the earliest known aquatic turtle.

Source: Proceedings of the Royal Society.



 220 million year old fossil turtle from China
 shows origin of turtle shell.
 November, 2008



 

Odontochelys semitestacea illustrations courtesy Marlene Donnelly and Institute of Vertebrate Palaeontology and Palaeanthropology, Beijing.

An ancestral turtle from the Late Triassic of southwestern China.

Chun Li, Xiao-Chun Wu, Olivier Rieppel, Li-Ting Wang & Li-Jun Zhao, Nature, Volume 456:497-501.


Abstract  The origin of the turtle body plan remains one of the great mysteries of reptile evolution. The anatomy of turtles is highly derived, which renders it difficult to establish the relationships of turtles with other groups of reptiles. The oldest known turtle, Proganochelys from the Late Triassic period of Germany1, has a fully formed shell and offers no clue as to its origin. Here we describe a new 220-million-year-old turtle from China, somewhat older than Proganochelys, that documents an intermediate step in the evolution of the shell and associated structures. A ventral plastron is fully developed, but the dorsal carapace consists of neural plates only. The dorsal ribs are expanded, and osteoderms are absent. The new species shows that the plastron evolved before the carapace and that the first step of carapace formation is the ossification of the neural plates coupled with a broadening of the ribs. This corresponds to early embryonic stages of carapace formation in extant turtles, and shows that the turtle shell is not derived from a fusion of osteoderms. Phylogenetic analysis places the new species basal to all known turtles, fossil and extant. The marine deposits that yielded the fossils indicate that this primitive turtle inhabited marginal areas of the sea or river deltas.

Source: Nature Volume 456 and Guardian UK Nature and Science.


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