Digitized reconstruction of Patagopelta. Image credit: CONICET
Ankylosauria is a clade of herbivorous, armored ornithischian dinosaurs subdivided in two major clades: the Ankylosauridae and the Nodosauridae. The most derived members of this group are characterized by shortened skulls, pyramidal squamosal horns, and tail clubs. Fossil evidence of armored dinosaurs from Gondwana is scarce. Patagopelta cristata, a new nodosaurid ankylosaur from the Allen Formation (Campanian–Maastrichtian), Rio Negro Province, Argentina, is the first species of ankylosaurus described for Argentina. The new specimen also offers new evidence that contributes to the understanding of the relationships among the ankylosaurs from Gondwana.
Patagopelta lived about 70 million years ago. The body length estimated is ∼2 meters (comparable in size with the nodosaurid Struthiosaurus from the Late Cretaceous of Europe). The generic name is derived from the word ‘Patago’ (referring to the Argentinian Patagonia) and ‘pelta’ (shield in Greek), in reference to the presence of a large number of osteoderms covering the dorsal surface of the body. The specific name ‘cristata‘ (crest in Latin) refers to the presence of crests on the anterior surface of the femur and the lateral osteoderm of the cervical rings.
Femur of Patagopelta cristata. From Riguetti et al., 2022
The ankylosaur material were collected by different research groups from the 1980s onwards. The holotype (MPCA-SM-78) is represented by a cervical half-ring element. The cranial material is represented by a single isolated tooth. The axial skeleton include a partial cervical neural arch, four dorsal vertebrae, two synsacral fragments and seven caudal vertebrae. The best preserved element is the femur. The femoral head is well developed and hemispherical, and it’s separated from the greater trochanter by a deep fossa. The fourth trochanter is placed proximally on the femoral shaft. The dermal elements include cervical and post-cervical osteoderms.
Phylogenetic analysis recovered Patagopelta within Nodosaurinae, along with other ‘mid’-Cretaceous nodosaurids from North America. These results support the proposal that South American ankylosaurs may have migrated from North America during the Late Cretaceous. The new study suggests that the small size of Patagopelta is linked to some event of dwarfism as in the case of Struthiosaurus from the Hateg Island.
References:
Facundo Riguetti, Xabier Pereda-Suberbiola, Denis Ponce, Leonardo Salgado, Sebastián Apesteguía, Sebastián Rozadilla & Victoria Arbour (2022) A new small-bodied ankylosaurian dinosaur from the Upper Cretaceous of North Patagonia (Río Negro Province, Argentina), Journal of Systematic Palaeontology, 20:1, 2137441, DOI: 10.1080/14772019.2022.2137441
Letters from Gondwana. 