A new genus and species of medium-sized sauropod dinosaur has been described from a single trunk vertebra found in the Department of Cesar, north-eastern Colombia.
A sauropod dinosaur chased by two carnivorous dinosaurs. Image credit: Lida Xing.
The newly-identified dinosaur species lived in the tropical lowland forests of what is now Colombia during the Jurassic period, some 175 million years ago.
“Most of the discoveries of dinosaurs in South America come from rocks from the Cretaceous period located in Argentina and Brazil,” said Universidad del Norte’s Professor Aldo Rincón Burbano and colleagues.
“Dinosaurs from the northern part of South America are much rarer, particularly during the Jurassic and Triassic periods, during the initial radiation of dinosaurs, when landmasses were still substantially interconnected.”
Named Perijasaurus lapaz, the new species belonged to Eusauropoda, a derived group of strictly herbivorous, quadrupedal dinosaurs with long necks.
“This new genus and species in the paleotropics allows us to understand a little more about the origin of the sauropods in the Jurassic, as well as how they set the stage for later sauropods from the Cretaceous,” Professor Burbano said.
The fossilized vertebra of Perijasaurus lapaz — about 55 cm tall and 45 cm wide — was found in exposures of the La Quinta Formation cropping out west of the town of Manaure in the Department of Cesar, north-eastern Colombia.
“Although Perijasaurus lapaz is represented by a single vertebra, that region of the skeleton provides the most information in sauropods, due to a series of laminae and other structures,” said Dr. Martín Ezcurra, a paleontologist at the Argentine Museum of Natural Sciences and CONICET.
“Perijasaurus lapaz lived in an environment of low slopes associated with a river and a forested area,” said Daniel Raad Pájaro, a researcher at the Universidad del Norte.
“We found fine sand and leaf debris in the sediment deposited in the area where the vertebra was originally found, and it is consistent with the sediment within the neural arch of the vertebra, which are only preserved near a floodplain, i.e., near the slopes of a river, a wooded area.”
The paleontologists also determined the evolutionary relationships of Perijasaurus lapaz through a computational analysis.
“Perijasaurus lapaz is part of the early radiation of sauropods, which includes species from southern South America, Africa, Asia and Europe,” said Dr. Harold Jiménez Velandia, a geologist at the University of Caldas.
The presence of Perijasaurus lapaz in the paleotropics of South America, together with its close phylogenetic relationship with geographically widespread species that inhabited low latitudes, suggests that sauropods diversified and dispersed fairly rapidly following a major anoxic event at the end of the Lower Jurassic, when portions of the oceans were depleted of oxygen over large geographic areas.
“What we see in the Early Jurassic, both in high latitudes and in the most tropical areas, is that sauropod species were evolutionarily and geographically interconnected, which is something that had also been seen with other groups of carnivorous and herbivorous dinosaurs,” Dr. Ezcurra said.
The findings were published this week in the Journal of Vertebrate Paleontology.
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Aldo F. Rincón et al. A sauropod from the Lower Jurassic La Quinta Formation (Dept. Cesar, Colombia) and the initial diversification of eusauropods at low latitudes. Journal of Vertebrate Paleontology, published online August 10, 2022; doi: 10.1080/02724634.2021.2077112
