First Triassic records of pterosaurs in the southern hemisphere.

Pachagnathus and Yelaphomte. Image credit: Jorge Blanco

Pterosaurs were the first flying vertebrates. Their reign extended to every continent and achieved high levels of morphologic and taxonomic diversity during the Mesozoic. The oldest-known pterosaurs appear in the fossil record about 219 million years ago. Most Triassic pterosaurs are small but already had a highly specialized body plan linked to their ability to fly: shoulder girdle with strongly posteroventrally enlarged coracoid braced with the sternum and laterally facing glenoid fossa; forelimb with pteroid bone and hypertrophied fourth digit supporting a membranous wing; and pelvic girdle with prepubic bone and strongly developed preacetabular process. By the Mid-Jurassic, pterosaurs had a worldwide distribution, but their known record is markedly biased toward the northern hemisphere. The description of two new specimens from Quebrada del Barro Formation in north-western Argentina are the first unequivocal Triassic records of pterosaurs in the southern hemisphere. Previous to this new work, the only record of a Triassic pterosaur in southern hemisphere was Faxinalipterus minima, from the Caturrita Formation in southern Brazil, although now is considered as a basal Ornithodira.

Pachagnathus benitoi, partial mandibular symphysis in right and left view. From Martinez et al., 2022

Yelaphomte praderioi was a small pterosaur. The holotype (PVSJ:914) is represented by a partial rostrum with the anterior part of both maxillae and palatine, and the posterior portion of both premaxillae. The highly fused bones of the rostrum may indicate its maturity and adult size. The generic name derived from the Allentiac language (spoken by the Huarpe) and means beast of the air, referring to the extreme pneumaticity of the rostrum of the new species and its capacity to flight. The specific name honors Angel Praderio, who discovered the new specimen.

Pachagnathus benitoi was a moderate-sized pterosaur. The holotype (PVSJ:1080) is a partial mandibular symphysis lacking anterior end, preserving one tooth and three alveoli from the the left side, and the roots of three teeth and two alveoli from the right side. The name comes from the words “Pacha” (Earth, in Aymara languaje) and “gnathus” (jaws, in Greek). The specific name honours Benito Leyes, who found the first fossils in Balde de Leyes.

 

References:

Martínez, R.N., Andres, B., Apaldetti, C. and Cerda, I.A. (2022), The dawn of the flying reptiles: first Triassic record in the southern hemisphere. Pap Palaeontol, 8: e1424.https://doi.org/10.1002/spp2.1424

Martínez, R.N., C. Apaldetti, G. Correa, C.E. Colombi, E. Fernández, P. Santi Malnis, A. Praderio, D. Abelín, L.G. Benegas, A. Aguilar-Cameo & O.A. Alcober. 2015. A new Late Triassic vertebrate assemblage from northwestern Argentina. Ameghiniana 52: 379–390.