WASHINGTON (Reuters) – A wonderful line of crocodile relatives that grew up in predators that swim fast in the sea, when dinosaurs dominated land adapted to life in the open sea, with a crucial evolutionary modification also present in whales.
A reconstruction of the life of the marine crocodile cricosaur from the Jurassic period is seen in this image released in Edinburgh, Scotland, Great Britain on April 20, 2020. Dmitry Bogdanov / Press Release REUTERS
But crocodiles did this more than 100 million years ago.
Research published on Monday detailed changes in the vestibular system of the inner ear – responsible for the sense of balance – in marine crocs called thalattosuchians, which appeared in the Jurassic period about 182 million years ago and died in the Cretaceous period about 125 million years ago .
Like whales, Thalattosuchians went through major skeletal changes as they evolved from ancestors that inhabited the land, turning limbs into fins, streamlining their bodies and developing a tail to swim hard.
They also altered their sensory systems, as evidenced by the changes in the inner ear revealed in the fossilized talatossucos skull scans. Three semicircular channels looped in the inner ear have become markedly fatter and smaller compared to those of their earthly relatives.
Whales, which first appeared about 50 million years ago, have a similar anatomy of the inner ear that evolved independently of the Talattosuchians.
"Changes in channel shape are more suited to life in the oceans, where buoyancy can support an animal, compared to land, where animals need a highly sensitive sense of balance to deal with gravity and complex landscapes," said Julia Schwab, a PhD student in geosciences at the University of Edinburgh and the lead author of the study published in the Proceedings of the National Academy of Sciences.
The similarities of the thalattosuchian whale's inner ear are an example of a phenomenon called convergent evolution, in which disparate organisms independently develop similar characteristics – such as the wings of extinct birds, bats and flying reptiles called pterosaurs – to adapt to similar environments.
The Talattosuchians reached about 10 meters in length. Some like teleosaurus and mamosaurus, who eat fish, remained semi-aquatic, still looking very much like a crocodile. Others, such as Metriorhynchus and Plesiosuchus, have been fully adapted to the open ocean, hunting for fish, squid cousins and even other marine reptiles.
They lived alongside other marine reptiles, some even larger. Previous studies have shown that some other groups of marine reptiles had similar adaptations in the inner ear.
"Talattosuchians are one of the most peculiar groups of animals that ever existed and it is shocking to me that they no longer receive attention," said Edinburgh University paleontologist and study co-author Steve Brusatte.
“What is really interesting is that we can say that the Thalattosuchians started to change their skeletons first – limbs in fins, flowing tail, etc. – which allowed them to enter the water and become better swimmers, and only later did their ears change, as their senses the systems had to evolve to keep up ”.
Reporting by Will Dunham; Editing by Sandra Maler
Our standards:The Thomson Reuters Trust principles.