The shady family tree of ancient crocodiles reveals unexpected twists and turns

The artist’s impression of a group of extinct fossil teleosauriodes – Macrospondylus. Credit: Nikolay Zverkov

Scientists studying the shadowy history of a group of prehistoric crocodiles have discovered an infinite truth – a fairly long pores and surprises will appear on everyone’s family tree.

Despite 300 years of research and a recent renaissance in the study of biological makeup, mysterious, predatory teleosauroids have long remained inaccessible.

The scientific understanding of this distant cousin of today’s long-nosed Garials has been hampered by the poor mastery of the evolutionary journey to date.

Unknown species

Researchers at the University of Edinburgh have identified a previously unknown type of teleosauroid and its seven close relatives – part of a dominant group. Jurassic coastal strips 190 to 120 million years ago.

Their analysis provides surprising insights into how teleosauroids adapted to the dramatic changes that took place during the Jurassic period, as the seas on Earth underwent many temperature changes.

“Our research only scratches the surface of teleosauroid evolution, but the findings are remarkable and raise interesting questions about their behavior and adaptations. These creatures represented some of the most successful prehistoric crocodile morphs of the Jurassic period, and there is much more to learn about them. ”

Dr. Michela M. Johnson Head of Studio, GeoScience School, University of Edinburgh

Research shows that not all teleosauroids are engaged in cutting and pushing lifestyles, and are caught in fish from the sea and swamps near other reptiles and shores.

Instead, they were a complex, diverse group that could use different habitats and search for different food sources. Scientists say that physical makeup is more diverse than previously thought.

Previous research has provided insights into the origin and evolution of metiorhynchids, the whale-like relatives of this fossilized crocodile, but little is known about teleosauroids.

500 fossils

To address this, a team of paleontologists examined more than 500 fossils from more than 25 sites around the world.

Advanced computer software has made it possible to gather a large amount of information about the anatomical similarities and differences of the group by examining skeletal, dental, and bone armor.

This information allowed the team to create a modern family tree of the group of teleosauroids, where two new large groups emerged, whose anatomy, abundance, habitat, geography, and eating styles differed significantly from each other.

The first group of teleosaurids were more agile in terms of living and feeding. The second group, known as Machimosaurids – which included the terrifying tortoise predators, Lemmysuchus and Machimosaurus – was more abundant and widespread.

Interesting features

The names given by the group of seven newly described fossils found in both teleosaurids and macimosaurids reflect interesting anatomical features – Proexochokefalos, meaning ‘big head with big tubers’, and Plagioftalmosuchus, a ‘side-eyed crocodile’.

There are even hints of different behavioral characteristics and unique places – Charitomenosuchus, meaning ‘elegant crocodile’, and ‘noble crocodile’ Andrianavoay from Madagascar.

Researchers named the newly discovered species Indosinosuchus kalasinensis in the Thai province of Kalasin, where the fossil – now housed at Maha Sarakham University –.

Recognition of I. kalacinensis suggests that at least two species lived in similar freshwater habitats during the last Jurassic period – an effective study as teleosauroids, with the exception of Machimosaurus, during this period.

“Just as the family trees of our ancestors and cousins ​​tell us our history, so does this giant new generation of teleosauroids shed light on their evolution. They were one of the most diverse and important animals in the Jurassic Ocean and have been familiar along the coast for tens of millions of years. ”
Professor Steve Brusatte, GeoScience School, University of Edinburgh, GeoScience School, Edinburgh University

Reference: “Phylogenetics of Teleosauroidea (Crocodylomorpha, Thalattosuchia) and their effects on ecology and evolution” Michela M. Johnson, Mark T. Young and Stephen L. Brusatte, October 8, 2020, PeerJ.
DOI: 10.7717 / peerj.9808

The study, published in the scientific journal PeerJ, was funded by the Council of Natural Sciences and Engineering of Canada, the SYNTHESYS Project and the Leverhulme Trust Research. The Paleontological Association and the Paleontological Society provided travel grants.

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