 |
| Chakisaurus nekul Nogueira, Rozadilla, Agnolín, Marsà, Motta & Novas, 2024 |
Abstract
The aim of the present contribution is to describe the first ornithischian species from the Huincul Formation (Cenomanian-Turonian, Upper Cretaceous) at the Pueblo Blanco Natural Reserve, Río Negro province, Argentina. The new species, named Chakisaurus nekul gen. et sp. nov., can be comfortably included among elasmarian ornithopods. The new species shows humeral anatomy that is congruent with smaller members of the clade (e.g. Anabisetia, Notohypsilophodon), and differs from larger taxa (e.g. Talenkauen, Mahuidacursor) which show humeral features probably related with graviportal habits, such as lack of shaft torsion and a distally located deltopectoral crest. This indicates that graviportal habits were probably acquired independently in elasmarians from other large-sized taxa, such as hadrosauroids. Caudal vertebrae of the new species also show a unique combination of characters shared with other elasmarians, which are absent in previously known ornithopods. These features indicate that some elasmarians had a protonic tail posture, which is unknown in other ornithischians and was previously considered unique to derived titanosaurian sauropods. The shape of transverse processes and neural spines of caudal vertebrae indicate that at least some elasmarians had improved cursorial habilities, that were convergently acquired by selected theropod clades.
Systematic paleontology
DINOSAURIA Owen, 1842
ORNITHISCHIA Seeley, 1887
ORNITHOPODA Marsh, 1881
ELASMARIA Calvo, Porfiri & Novas, 2007
Chakisaurus nekul gen. et sp. nov.
Conclusions:
The new genus and species Chakisaurus nekul is described here based on several juvenile and adult specimens. It constitutes the first named ornithischian 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 constitutes an important addition to the knowledge of this region of the ornithopod body. Furthermore, its humeral shape is very different from other ...
Rodrigo Alvarez Nogueira, Sebastián Rozadilla, Federico L. Agnolín, Jordi A. Garcia Marsà, Matias J. Motta and Fernando E. Novas. 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
