An article published in the journal “Palaeontology” describes a research which concluded that mosasaurs were warm-blooded. These animals were marine reptiles that became extinct along with the dinosaurs about 66 million years ago, at the end of the Cretaceous period. Dr. Alberto Perez-Huerta, a professor of geology at the University of Alabama, and then students T. Lynn Harrell Jr. and Celina Suarez believe they have found evidence that mosasaurs were warm-blooded and not cold-blooded, like other scientists claimed.

Mosasaurs (photo ©Ghedoghedo) constitute a scientifically family called Mosasauridae that lived in the Late Cretaceous, between 95 and 65 million years ago. They probably descended from aigialosaurs, reptiles similar to monitor lizards, with which they’re related. For about 20 million years they were the dominant marine predators following the extinction of ichthyosaurs and the decline plesiosaurs.

Given their relation with today’s monitor lizards and even snakes, many scientists believe that mosasaurs were cold-blooded and a 2010 research also suggested that possibility. Dr. Alberto Perez-Huerta wasn’t convinced because that research focused on extinct animals including plesiosaurs and ichthyosaurs togegher with mosasaurs but not warm-blooded animals.

The new study used the analysis of oxygen isotopes based on their correlation with the animal’s body temperature. There’s a significant difference between warm-blooded species, which maintain a higher body temperature independently of the marine environment in which they live, and cold-blooded ones, whose temperature is lower and is affected by their environment.

The analysis was performed on mosasaur fossils in the collection of the University of Alabama’s Alabama Museum of Natural History compared with other animals. Some of them were cold-blooded, such as fish and turtles of the same period, and other contemporary warm-blooded such as birds, whose bones were analyzed.

The result is that mosasaurs body temperature is similar to that of today’s birds. It’s a trend present in the various species belonging to the Mosasauridae family analyzed in this research regardless of the various animals’ size. In technical terms they were endothermic animals, commonly called warm-blooded.

In recent years various evidence were found that some species of dinosaurs were warm-blooded, the latest one in a study published in October 2015. As for reptiles and especially mosasaurs the issue has been a source of controversy. This new research offers a clear opinion but possibly others will come in the future.