A sauropod from the Lower Jurassic La Quinta Formation (Dept. Cesar, Colombia) and the initial diversification of eusauropods at low latitudes

RINCON, ALDO. F.; RAAD PÁJARO, D. A.; JIMÉNEZ VELANDIA, H. F.; EZCURRA, M. D.; WILSON MANTILLA, J. A.

JOURNAL OF VERTEBRATE PALEONTOLOGY

SOC VERTEBRATE PALEONTOLOGY

Lugar: Lawrence; Año: 2022

0272-4634

The northern-most occurrence of Sauropoda in South America was collected in the 1940s from Early–MiddleJurassic-aged continental sediments on the western flank of the Serranía del Perijá in Colombia. Relocation of the site and repreparationof the specimen, a well-preserved dorsal vertebra, provide important information about the initial diversificationof sauropods at low latitudes. The specimen possesses autapomorphies and a unique combination of character states (e.g.,divided centropostzygapophyseal lamina, strongly dorsally arched postzygapophyseal facets) that diagnose it as the newgenus and species Perijasaurus lapaz. A medium-sized early eusauropod, Perijasaurus inhabited tropical lowland forestedareas around the Toarcian–Aalenian boundary. Our phylogenetic analysis recovers Perijasaurus near the base ofEusauropoda, in an unresolved position near Cetiosaurus, Patagosaurus and kin (Bagualia, Spinophorosaurus,Nebulasaurus), and more deeply nested eusauropods. The phylogenetic position of Perijasaurus bolsters the idea thateusauropods achieved a broad geographic distribution during the Early–Middle Jurassic, before the deeper fragmentationof Pangea and after the Toarcian faunal turnover documented at high southern latitudes. Perijasaurus and other basallydiverging sauropods display an intermediate level of bone weight reduction in the axial column that represents anantecedent to the more highly developed pneumatic system characterizing Neosauropoda.