A paper published earlier this month in the journal Cretaceous Research announces the discovery of a previously undocumented genus and species of medium-sized ornithopod dinosaur.

An artist’s impression of Chakisaurus nekul. Image credit: Sci.News / UnexpectedDinoLesson / CC BY 4.0 Deed.

The new dinosaur lived in what is now Patagonia, Argentina, during the Late Cretaceous epoch, between 100 and 90 million years ago.

Dubbed Chakisaurus nekul, the species was between 2.5 and 3 m in length and stood about 0.7 m tall.

The ancient beast belongs to Elasmaria, a clade of ornithopod dinosaurs known from the Cretaceous deposits of South America, Antarctica, and Australia.

“Despite the fact that elasmarians are widespread along Cretaceous beds from South America, Australia, Antarctica and South Africa, several aspects of their anatomy and diversity remain obscure,” said lead author Dr. Rodrigo Alvarez Nogueira and his colleagues from the Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’ – CONICET and the Universidad Maimonides.

“As for example, tail anatomy remains poorly studied, particularly for South American members of the clade.”

“On the other side, the phylogenetic relationships and character distribution within elasmarians remain poorly explored.”

The postcranial remains of multiple individuals of Chakisaurus nekul were found in the Huincul Formation at the Pueblo Blanco Natural Reserve, in northern Río Negro province, Argentina.

“The Huincul Formation yields one of the most diverse vertebrate assemblages, including fishes, turtles, crocodiles, and dinosaurs,” the paleontologists said.

“Regarding dinosaurs, saurischians are dominant, counting with many species of sauropods and theropods.”

“On the other hand, ornithischian remains from the Huincul Formation are only represented by an isolated ungual phalanx of an indeterminate ornithopod.”

According to the team, Chakisaurus nekul constitutes the first named ornithischian species from the Huincul Formation and sheds light on tail and humeral anatomy in elasmarians.

“Caudal anatomy of elasmarians, and ornithopods in general, is poorly known, and thus, Chakisaurus nekul constitutes an important addition to the knowledge of this region of the ornithopod body,” the researchers said.

“Furthermore, its humeral shape is very different from other medium-sized elasmarians, resembling smaller taxa, and being suggestive that this clade included species of divergent locomotory habits.”

“In this aspect, larger elasmarians show a combination of characters that indicate that some members of the clade possessed quadrupedal or graviportal habits, and that they probably constitute a subclade of their own.”

“This also points to the fact that the anatomical diversity of elasmarians is far from being well understood.”

“The novel anatomical information provided by Chakisaurus nekul lends support to the idea that elasmarians were very different from other ornithopod lineages and that further studies are needed to recognize their uniqueness and elucidate their diversity in the southern landmasses.”


Rodrigo Alvarez Nogueira et al. 2024. A new ornithopod from the Upper Cretaceous (Huincul Formation) of northwestern Patagonia, Argentina: Implications on elasmarian postcranial anatomy. Cretaceous Research 159: 105874; doi: 10.1016/j.cretres.2024.105874

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