Evrim Yazgin
Cosmos science journalist
Palaeontologists have found evidence that dozens of alligator-sized amphibians died together about 230 million years ago. It’s unclear whether such a die-off was common, or if something more sinister was behind the creatures’ demise.
The animals lived during the Triassic period which lasted from 252 to 201 million years ago. The Triassic is the first of the 3 periods which are commonly referred to as the “Age of Dinosaurs”.
The fossils are described in a paper published in the journal PLOS One.
At least 19 Buettnererpeton bakeri individuals were uncovered at the site called Nobby Knob in the US state of Wyoming. More than half of the known B. bakeri specimens are at the site.
B. bakeri could easily grow to more than 1m in length. They were part of an ancient group of amphibians called temnospondyls. These were 4-legged amphibians which could grow to massive sizes, with some looking like gigantic newts.
Temnospondyls were among the first vertebrate animals to conquer land some 350 million years ago. They were common during the Triassic, but most went extinct as crocodiles and dinosaurs evolved and dominated freshwater ecosystems.
It’s thought the last of their kind lived in what is now southeastern Australia – the 3m-long Koolasuchus cleelandi which went extinct about 120 million years ago during the Cretaceous period.
Most temnospondyls were semiaquatic, but some had adapted to become almost fully land-based, returning to water only to breed.
This may explain why so many B. bakeri congregated together at Nobby Knob 230 million years ago. Other such concentrations of temnospondyls have been discovered at sites around the world.
Nobby Knob was a floodplain during the Triassic. The layers uncovered by palaeontologists reveal fine-grained ancient soils and finely layered sediments.
The B. bakeri remains aren’t arranged in a pattern which would have led the palaeontologists to suggest strong currents. The water must have been very calm, helping preserve even very fragile parts of the animals’ bodies.
“This assemblage is a snapshot of a single population rather than an accumulation over time” says Aaron Kufner from the University of Wisconsin-Madison, US.
The site represents an opportunity to study this species and also the causes of such mass mortality events among temnospondyls.
