A team of Australian scientists led by UNSW Sydney palaeontologist Lachlan Hart has calculated the body mass of two ancient amphibians.
The last of the temnospondyls – amphibians that look more like crocodiles – became extinct during the Cretaceous period, about 120 million years ago, after thriving on Earth for more than 200 million years.
Now a team of scientists led by Lachlan Hart, a palaeontologist and PhD candidate in the School of Biological, Earth & Environmental Sciences at UNSW Sydney, has assessed various methods of estimating the weight of these unique extinct animals. The team's study is published in Palaeontology.
"Estimating mass in extinct animals presents a challenge, because we can't just weigh them like we could with a living thing," said Mr Hart. "We only have the fossils to tell us what an animal looked like, so we often need to look at living animals to get an idea about soft tissues, such as fat and skin."
Temnospondyls as case studies
Mr Hart said temnospondyls were "very strange animals".
"Some grew to enormous sizes, six or seven metres long. They went through a larval (tadpole) stage just like living amphibians. Some had very broad and round heads – such as Australia's Koolasuchus, recently named as the Victorian State Fossil Emblem – and others, like the temnospondyls we used in this study, had heads that were more croc-like."
The 1.8 metre-long Eryops megacephalus lived during the Permian period in what is now the USA, while the slightly longer Paracyclotosaurus davidi is known from the Triassic of Australia. The more aquatically inclined Paracyclotosaurus was the heftier of the two, tipping the scales at roughly 260 kilograms, where Eryops was a more modest 160 kilograms.
"The size of an animal is important for many aspects of their life," said Mr Hart. "It impacts what they feed on, how they move and even how they handle cold temperatures. So naturally, palaeontologists are interested in calculating the body mass of extinct creatures so we can
