Evrim Yazgin
Cosmos science journalist
A 135-million-year-old crocodile fossil has been found which belongs to an unusual extinct family called Metriorhynchidae.
Enalioetes schroederi lived in the shallow seas that covered much of what is now Germany during the Cretaceous period (145–66 million years ago). It is known from a skull fossil found in the Valanginian Stadthagen Formation in Hanover, northwestern Germany.
The species is described for the first time in a paper published in the Journal of Systematic Palaeontology.
More than a dozen species of Metriorhynchidae have been found in Europe as well as South and Central America.
Metriorhynchidae were fully aquatic crocodyliforms that are among the most well-adapted marine reptiles. They had dolphin-like bodies, smooth skin and tailfins. Metriorhynchids fed on squid, fish and even other marine reptiles.
Crocodilians and turtles were the only marine or semiaquatic reptiles to survive the mass extinction which saw the demise of the non-avian dinosaurs 66 million years ago. However, Metriorhynchidae were already on the decline during the Cretaceous.
Metriorhynchids fossils are most commonly found dating to the earlier Jurassic period (201–145 million years ago).
E. schroederi’s skull makes it the best preserved metriorhynchid from the Cretaceous.
“The specimen is remarkable as it is one very few metriorhynchids that is known by a three-dimensionally preserved skull,” says first author Sven Sachs from the Natural History Museum, Bielefeld in Germany. “This allowed us to CT scan the specimen and so we were able to learn a lot about the internal anatomy of these marine crocodiles. The remarkable preservation allowed us to reconstruct the internal cavities and even the inner ears of the animal.”
Though only just identified as a new species, the skull was discovered more than a century ago by German government architect D. Hapke in a quarry.
The specimen was presumed lost during World War II.
Sachs and his team determined it was a new species by comparing it to fossils from other museum collections.
“Enalioetes gives us fresh insight into how metriorhynchids were evolving during the Cretaceous Period. During the Jurassic, Metriorhynchids evolved a body-plan radically different from other crocodiles – flippers, tailfin, loss of bony armour and smooth scaleless skin. These changes were adaptations to an increasingly marine lifestyle.
“Enalioetes shows us that this trend continued into the Cretaceous, as Enalioetes even larger eyes than other metriorhynchids (which were already big by crocodylian standards) and the bony inner ears were even more compact than other metriorhynchids, a sign that Enalioetes was probably a faster swimmer.”
