Jurassic teleosaurids

Three species of Jurassic Machimosaurus. Illustrations by Dmitry Bogdanov, from Young et al. (2014).

Jurassic sea crocs lived similar lives to their modern relatives

Extinct crocodile-like creatures had lifestyles similar to those of today’s crocodiles.

Members of a group of extinct reptiles known as teleosaurids adapted to certain habitats that mirror the patterns found in today’s modern crocodiles, new research has revealed.

Specialised living

A large telesaurid species in the genus Machimosaurus was adapted to open-water living and diving in Jurassic seas, while several smaller species lived in more specific coastal areas and may have basked on the shore.

This pattern of one large, open-water species and several smaller coastal or freshwater species exists in crocodiles today.

A team of researchers led by the University of Edinburgh re-examined fossils of all the members of the Machimosaurus genus discovered so far. Machimosaurus is a crocodylomorph - a group of creatures that includes modern and extinct crocodile relatives. The research team included Museum palaeontologist Dr Lorna Steel and the study included some specimens from the Museum.

Separating species

Until now, scientists were unsure how many species of Machimosaurus there were. But by studying characteristics of the fossils, including body length, skull and jaw shape, and tooth patterns, researchers have discovered that there are at least three different species.

One of these three species, Machimosaurus hugii, appeared adapted to open-water living. It was over nine metres long, and a fast swimmer with muscles developed for diving.

'The largest species was 9.26 metres long, making it the largest crocodylomorph of the Jurassic,' said Dr Steel.

Fossils of M. hugii have been discovered in ancient oceans from Switzerland to Portugal. Shells of ancient marine turtles have been found with teeth marks matching M. hugii.

Coastal crocs

The other two species had smaller bodies of only five to six metres in length, which were not as well adapted to diving. The species M. mosae had a robust skeleton and a thick set of ribs that could have helped it stay steady in more turbulent waters around the coast.

M. mosae also had an ornamented skull with many undulations. This could have helped the animal regulate its body temperature when basking on land, as studies on modern caimans have shown.

The third species, M. buffetauti, was similar to M. mosae, but with a smoother skull. This suggests it was adapted to a different lifestyle, but probably still lived near the coast.

M. buffetauti and M. mosae would have been geographically limited as they were adapted to their particular coastal environments, whereas M. hugii would have been able to cross the open sea.

Parallel patterns

Today, the saltwater crocodile (Crocodylus porosus) found in Asian and Australian waters is the largest living reptile in the world. Like its ancient relative M. hugii it can be found in a number of oceans in the region. Five other smaller species exist in its range, but they are limited to specific areas.

A similar situation exists in the Americas, where the American crocodile (Crocodylus acutus) is the largest and most widespread among the four living American species.

'Interesting parallels can be seen between groups of ancient crocs and those living today,' said research leader Dr Mark Young of the University of Edinburgh.

'With more fossils being discovered, we look forward to learning more about this giant group of Jurassic predators.'