The crocodiles that lived with the dinosaurs walked more upright than the current ones

At footprints (fossil footprints) assigned to crocodiles they are not very abundant in the world fossil record. However, the province of Soria is an exception, being one of the few places on the planet where traces of these reptiles have been found.

In BretĂșn, city of Highland Region, popular for its dinosaur sites, the footprints of some fossil specimens have been found over 20 years ago. these reptiles, known by the scientific name of crocodylopodus, they lived with dinosaurs in the Lower Cretaceous, about 145 million years ago.

Now, a research team from the group Aragosaurus-IUCA from the University of Zaragoza (JOIN) and the Catalan Institute of Paleontology Miquel Crusafont (PCI) he has studied in detail the morphology of these ichnites.

When compared to those of modern crocodiles, the researchers found that the tracks were considerably narrower and with the feet and hands closer together.

“Because of their shape, the footprints of these fossil reptiles are very similar to those of present-day crocodiles, both in handprints and foot prints. However, some caught our attention. trait differencesthat is, in the sequence of footprints they left while walking”, he explains. Diego Castanerastudy leader.

Comparing them with those of modern crocodiles, the researchers found that they were considerably narrower and with closer feet and hands. “Furthermore, they do not show signs of the tail, the intestine or the drag of the ends, something very common in the traits of their current descendants”, says Castanera.

Comparison of these footprints with a wealth of fossil and extant footprint data led researchers to conclude that these extinct crocodiles walked on a more upright and more agile position than their current descendants.

What do we know about this extinct crocodile?

Most of the footprints studied are small, no more than 7 cm in length, and are estimated to correspond to crocodiles no more than one meter in length. What the researchers failed to answer is the presence of footprints of three different sizes. “It could be animals of different ages or it could be due to size differences between males and females. Or it could even be that both circumstances occurred at the same time. Eduardo Puertolas-Pascualresearcher from Zaragoza and co-author of the study.

The experts also compiled data on the crocodile species that inhabited the Iberian Peninsula in the Lower Cretaceous, to try to determine which species is the author of the footprints. However, with the current data it is not possible to conclude to which specific group of crocodiles they belong. There are several candidates: among them, goniopholes, atoposaurus or bernissartiawhich were the dominant ecosystems at the time.

“What we do know is that the animal that left its footprints had longer forelimbs in relation to the total length of the body, a forward center of mass is lighter or shorter tail than the current ones. These crocodiles would be better adapted for locomotion in terrestrial environments”, concludes PuĂ©rtolas-Pascual.

Comparison of the remains of Crocodylopodus (above) and an extant crocodile (below) with the main differences

Comparison of the remains of Crocodylopodus (above) and a current crocodile (below) with the main differences (greater width and angle of passage and tail markings in the current ones). /PCI

Reference:

Castanera, D., Pascual-Arribas, C., Canudo, JI, & Puértolas-Pascual, E. (2022). a new look at Crocodylopodus meijidei: implications for locomotion of crocodylomorphs. Vertebrate Paleontology Journal, 41:5, e2020803. IT HURTS:10.1080/02724634.2021.2020803

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