A mass extinction that occurred over 200 million years ago, killed off a slew of huge predators, including hefty beasts that looked like crocodiles and enormous armadillos, according to new research.
Some of the prehistoric predators - animals known collectively as the early pseudosuchians - likely preyed on certain dinosaurs, which later evolved some of impressive characteristics of the ancient pseudosuchians. Those included features like sturdy body armour and strong tails for whacking enemies.
"It is likely, therefore, that dinosaurs prospered to some extent as a result of the extinction of most pseudosuchians and many other groups at the end of the Triassic," says co-author Richard Butler, a palaeontologist at Ludwig-Maximilians-Universität.
He adds that some evidence suggests dinosaurs "had better locomotor and breathing systems than pseudosuchians," so they thrived in the Jurassic after the mass extinction.
As for what caused that die-off, researchers suspect anenormous burst of volcanic activity, as part of the Atlantic Ocean's formation, led to dramatic increases in atmospheric carbon dioxide and rapid global warming.
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