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New long-necked dinosaur helps rewrite the evolutionary history of sauropods in South America

Patagosaurus is from Patagonia and is one of the sauropods most closely related to Perijasaurus. Credit: Pol et al. (2020)

A medium-sized sauropod dinosaur inhabited the tropical lowland forested region of the Serranía del Perijá in northern Colombia about 175 million years ago, according to a new study by an international team of researchers published in the Journal of Vertebrate Paleontology.

The new species is a long-necked herbivorous dinosaur known for a single trunk vertebra that is about half a meter high and wide. The vertebra has a distinct pattern of bony struts identifying it as the new dinosaur species Perijasaurus lapaz (pear-EE-hah-SOW-rose la-PAHZ) – named in recognition of the mountainous area where it was found and the 2016 Peace treaty that allowed scientists to continue their research decades after the fossil remains were found in 1943.

Perijasaurus is the northernmost occurrence of a sauropod in South America and represents an early stage in their evolutionary history.

“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 Cretaceous sauropods,” said study lead author Aldo. Rincón Burbano, professor of physics and geosciences at the Universidad del Norte in Colombia.

The fossil was first discovered in 1943 during a geological mapping campaign by the Tropical Oil Company. The specimen was taken to the collections of the University of California, Berkeley and tentatively described in 1955.

University of Michigan paleontology curator and professor Jeff Wilson Mantilla examined the specimen as a graduate student in 1997 and later developed a project supported by the Fulbright Foundation to study the early evolution of sauropods in Colombia.

As part of that project, the Colombian specimen was loaned to UM, where chief preparer William Sanders removed glue and plaster, greatly increasing the visibility of anatomical detail and reducing the overall weight of the specimen.

“After repair of the fossil, we were able to better visualize the delicate bony laminae connecting the protuberances of the vertebra – the spine, the intervertebral joints, the rib joints -. The architecture of those connections provides critical morphological information that identifies as a new species and places it in the sauropod family tree,” Wilson Mantilla said.

A 3D model of the instance is hosted on the University of Michigan Online Repository of Fossils.

A conflict since 1964 between Colombian armed forces, the FARC guerrilla group and paramilitary groups made it unsafe to conduct research in Serranía del Perijá, near the Colombia-Venezuela border, until the 2016 peace accords.

Since then, the research team has worked to determine with greater precision where the fossil was found. A satellite image of the region was superimposed on a 1955 hand-drawn map showing the fossil’s location. Another clue was provided by sediment removed from the vertebra itself during the preparation process, which allowed the team to determine from which specific layer the bone had formed.
collected. Fieldwork at the site and adjacent sites helped reconstruct the paleoenvironment in which the dinosaur lived.

“Perijasaurus lived in an environment of low slopes associated with a river and a forest area. We found fine sand and leaf litter in the sediment deposited in the area where the vertebra was originally found, and it corresponds to the sediment in the neural arch of the vertebra, which is preserved only near a floodplain, that is, near the slopes of a river, a wooded area,” said Daniel Raad, a former geology student at the Universidad del Norte.

Most dinosaur discoveries in South America come from Cretaceous rocks in Argentina and Brazil. Dinosaurs from the northern part of South America are much rarer, especially during the Jurassic and Triassic periods, during the first dinosaur radiation, when land masses were still largely interconnected.

“Although Perijasaurus is represented by a single vertebra, that part of the skeleton provides the most information in sauropods, because of a series of laminae and other structures,” said Martín Ezcurra, a paleontologist and associate researcher with the CONICET (Argentina’s National Council for Scientific and Scientific Research). Technical Research) and Chief Curator of Paleovertebrates at the Argentine Museum of Natural Sciences.

The researchers were able to determine the evolutionary relationships of Perijasaurus through a computational analysis focused on early and Middle Jurassic sauropods.

New long-necked dinosaur helps rewrite the evolutionary history of sauropods in South America

A single trunk vertebra about half a meter high and wide has enabled scientists to identify a new species of long-necked herbivorous dinosaur. Credit: UM Online Repository of Fossils viewer developed by the UM Museum of Paleontology

“Perijasaurus is part of the early irradiation of sauropods, including species from southern South America, Africa, Asia and Europe,” said Harold Jiménez Velandia, a geologist at the University of Caldas.

The presence of Periasaurus in the paleotropics of South America, along with its close phylogenetic relationship to geographically widespread species living at low latitudes, suggests that sauropods diversified and dispersed quite rapidly after a major anoxic event at the end of the Lower Period. Jurassic, when parts of the oceans were depleted of oxygen over large geographic areas.

“What we see in the early Jurassic, both at high latitudes and in the most tropical regions, is that sauropod species were evolutionarily and geographically linked, something that had also been seen with other groups of carnivorous and herbivorous dinosaurs,” Ezcurra said.

Sauropods are the largest animals to have walked on land, some reaching an estimated length of 49 meters and weighing up to 57 tons. Their ability to support their weight and move their bodies efficiently comes from a series of adjustments to reduce weight and increase bone support.

An anatomical feature of sauropods is vertebral pneumatics. Essentially, extensions of the air sac system of the lungs extend into the spine and basically remove the internal bone, effectively relieving the skeleton.

“By the late Jurassic, sauropods had developed highly pneumatic vortices dotted with air spaces that removed half to three quarters of bone weight. Perijasaurus represents an evolutionary antecedent in which the pneumatic invasions are much simpler and more limited, removing less than a quarter of the bone volume.” said Wilson Mantilla.

He said the team will continue to focus on regions in Colombia with exposure to Jurassic sediments.

“Colombia is emerging as a country with great potential to contribute to the paleontology of the continent and the world,” Wilson Mantilla said.

Perijasaurus is permanently stored at the University of California Museum of Paleontology in Berkeley, California.

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More information:
Aldo F. Rincón et al, A sauropod from the La Quinta Formation in the Lower Jurassic (Dept. Cesar, Colombia) and the initial diversification of eusauropods at low latitudes, Journal of Vertebrate Paleontology (2022). DOI: 10.1080/02724634.2021.2077112

Specimin 3D Model: umorf.ummp.lsa.umich.edu/wp/wp … e=1673&extension=ctm

Provided by the University of Michigan

Quote: New long-necked dinosaur helps rewrite the evolutionary history of sauropods in South America (2022, August 10) retrieved August 10, 2022 from https://phys.org/news/2022-08-long-necked- dinosaur-rewrite-evolutionary-history.html

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