22 September 2016
Amy Middleton
Amy Middleton is a Melbourne-based journalist.
A long-lost reptile hailing from the Triassic period has been found to closely resemble dinosaurs that lived around 100 million years later, a new study suggests.
A group of scientists led by Michelle Stocker, a geoscientist at Virginia Polytechnic Institute and State University in the US, found that the newly discovered crocodile-like reptile Triopticus primus sported a dinosaur-like dome-shaped head.
The remains, reported in Current Biology, were found in a fossil hotspot in the Otis Chalk quarries in Texas, a site which represents the oldest and best-documented terrestrial record of the development of archosaurs during the Late Triassic.
“We were surprised to find something like Triopticus primus at all!” Stocker says.
“There was nothing else like that known from the Triassic period, and we wouldn’t have guessed that we would find something that looked like that outside of the Cretaceous period.”
Land-dwelling life about 230 million years ago during the Triassic period mostly consisted of reptiles, beaked herbivores and croc-like amphibians.
The dinosaurs that lived during the Triassic were small carnivorous types that walked on two legs – a far cry from this archosaur, which looks a lot more like something out of the much later Cretaceous and represents a very early iteration of today’s crocodiles.
The archosaur’s dome-shaped skull isn’t only a surface trait, either – Stocker says her team was surprised to find the skull’s internal structure also resembled dinosaurs from tens of millions of years later.
The finding suggests a convergence in the evolution of reptiles around the time of the Triassic.
Researchers explain this development by pointing to a period of high genetic selection that may have taken place in the wake of mass extinction events in the previous era.
“The Triassic period may have been a time of experimentation with respect to body plans,” Stocker explains.
“Reptiles were diversifying after the end-Permian mass extinction, and this may have been an opportunity for evolution to operate quickly and with few constraints.”