Teeth reveal surprising diversity of Cretaceous reptiles at Argentina fossil site

A study published on September 8, 2021, in the open-access journal PLoS ONE by Ariana Paulina-Carabajal and colleagues from INIBIOMA and CONICET in Argentina revealed that in regions where skeletons are rare, isolated teeth play a crucial role in understanding ancient reptile-dominated ecosystems. The Cerro Fortaleza locality in Santa Cruz, Argentina, known for its importance in the history of dinosaurs and Mesozoic reptiles, appeared surprisingly sparse in Late Cretaceous deposits. However, researchers expanded their understanding of reptile diversity at this site by studying teeth.

During fossil excavations in December 2016, 13 teeth and 9 tiny osteoderms (armor-like skin bones) were found, representing various ancient reptiles. These remains confirmed the presence of three types of dinosaurs: carnivorous abelisaurs, armored ankylosaurs, and long-necked titanosaurs. Additionally, most of the teeth were identified as belonging to peirosaurs, land-dwelling relatives of crocodiles. Although exact species identification was challenging due to the scarcity of fossils, the findings indicated a much more diverse reptile population at the Cerro Fortaleza locality than previously known.

Ankylosaur osteoderm, thin sections. Credit: Dr. I. Cerda.

The study’s findings provide valuable insights into the geographic ranges of certain animals. The presence of armored dinosaurs (ankylosaurs) at the Cerro Fortaleza site creates a link between records of these dinosaurs from both northern Patagonia and southern Antarctica. Additionally, the discovery of peirosaurs (croc-cousins) represents the southernmost record of this group. These findings highlight the significance of small fossil remains, like teeth and dermal ossicles, in enhancing our understanding of ancient environments and the dispersal patterns of creatures in regions where complete skeletal remains are scarce.

The researchers emphasize that sometimes full skeletons may not be available, and in such cases, tiny fossils play a crucial role in revealing the diversity of dinosaurs and crocodiles at a site. The study showcases a unique faunal association previously undiscovered, particularly highlighting the records of ankylosaur dinosaurs and peirosaurid notosuchians as the most austral findings so far in South America.

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