August 2016

Remains of a flying reptile from the Jurassic were found in Chubut

These are the first remains of pterosaurs found in the Province of Chubut. The excellent state of preservation of cranial fossils reveals information about brain evolution and adaptation to flight of this particular group of flying reptiles.

Scientists in charge of this investigation unveiled a new species of pterosaur from the Early­Middle Jurassic of Chubut. The team have named it ​Allkaruen ​ koi , from the native Tehuelche ​ words ​ ‘all’ for ‘brain’,​ ​ ‘karuen’ for ‘ancient’, ​ and​ ‘koi’ for lake; referring to the type of sediment where the fossils were found.

​ Thanks to their excellent state of preservation, the cranial remains provide new information about the origin, tempo and mode of evolution of the braincase in this particular group of flying reptiles. Until now, descriptions of the neuroanatomy had been limited to a few species, and the information available on intermediate stages in the evolution of pterosaurs was scarce.

About 170 million years ago, the world’s ecosystems were very different than today. Patagonia in particular was much warmer and humid, and a huge diversity of plants and animals, now extinct, lived here ­ pterosaurs among them. Pterosaurs are an extinct group of flying reptiles that lived during most of the Mesozoic Era and they were the first vertebrates to conquer the aerial environment.

Allkaruen fossils were found in the north ­center of Chubut Province, a few kilometers from the village of Cerro Condor, in Early Jurassic outcrops belonging to an ancient lake where these reptiles probably fell.

The scientific team studied the neurocranium​ ​ anatomy by computed tomography, in order to analyze three­dimensionally the cranial mold and the inner ear. The team conducted a comprehensive phylogenetic analysis of the group, including these cranial data and other anatomical features. The intermediate ​ position of Allkaruen ​ on the evolutionary tree of pterosaurs, plus the data obtained from the cranial studies, provide new information on the typical transformation from the earliest pterosaurs into the derived condition of pterodactyls. “The importance of this discovery is that it is a pterosaur from the Lower­Middle Jurassic limit, showing an intermediate stage in the evolution of the brain of pterosaurs and their adaptation to the aerial environment”, says Diego Pol, PhD, (CONICET­ Museo Paleontológico Egidio Feruglio), who was part of the research team.

The discovery was published in the scientific journal Peer J by the interdisciplinary group formed by Dr. Laura Codorniú (CONICET­Universidad Nacional de San Luis), Dr. Diego Pol (CONICET­Museo Paleontológico Egidio Feruglio), Dr. Ariana Carabajal (CONICET­Instituto de Investigaciones en Biodiversidad y Medioambiente, Río Negro) and Dr. David Unwin (University of Leicester, United Kingdom).

A paleoartist’s reconstruction of a ptesosaur. Credit: Gabriel Lío

Aerial success assured

Pterosaurs were good flyers and gliders, thanks to their extraordinary adaptation to air. Like birds, their bones were pneumatized (​hollowed​) to lighten the weight of the skeleton and the keel, an extension of the sternum, was highly developed indicating the presence of powerful pectoral muscles to mobilize the wings. However, the similarity with birds is only superficial, and the origin in common between the two groups is very remote. Pterosaurs had reptilian features, such as teeth and the absence of feathers. Unlike birds, wings membrane was supported by one digit, the fourth, which was highly elongated in comparison with the others.

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