For the latest study, published in Biology Letters, Butler and colleague Olja Toljagić assessed changes in pseudosuchians that occurred during the critical Late Triassic and Early Jurassic periods.
The study shows that during the extinction event 201 million years ago, these animals declined rapidly, with only one lineage surviving into the Jurassic. Some of the animals evolved into ancestors of today's alligators and crocodiles. Another lineage, referred to as the "bird-line archosaurs," consisted of the non-avian dinosaurs and their species that later evolved into modern birds.
Luck, in part, helps to explain why some animals died, while others survived.
"Selectivity of mass extinction events is sometimes linked with body size, ecological constraints and competition, while other times it could be related to just pure luck of the survivors," Toljagić explained.
Stephen Brusatte, a paleontologist at the University of Edinburgh, previously studied how crocodile-line archosaurs changed during the Triassic and across the Triassic-Jurassic boundary.