Inside the head of one of Australia’s smallest fossil crocodiles

About 13.5 million years ago, northwest Queensland was home to an unusual and very small species of crocodile, and now scientists are revealing its secrets. Researchers at the University of Queensland have used state-of-the-art technology to reveal previously unknown details about the anatomy of the prehistoric Trilophosuchus rackhami.

Faculty of Science Ph.D. candidate Jorgo Ristevski said it is the most detailed study ever conducted on the skull anatomy of an extinct crocodile from Australia.

“Through micro-CT scanning of the beautifully preserved skull, we were able to digitally separate each bone,” said Mr. Ristevski. “We estimate that in adulthood Trilophosuchus rackhami would have been between 70 and 90 centimeters in length and weigh one to two kilograms, which was very small compared to most crocodiles today.

“This was a really unique looking crocodile, with a short snout and three distinct ridges on the top of its skull.”

Trilophosuchus rackhami means Rackham’s three-crested crocodile, which was named in 1993 in honor of Alan Rackham, who now manages the Riversleigh Fossil Discovery Center on Mt Isa.

Mr. Ristevski said paleoneurology, a field that studies the brain and nervous system of fossil species, can provide crucial insights into the animal’s evolution, morphology and even behavior.

“For one of the studies, I digitally brain cavity of Trilophosuchus rackhami and found that it resembles that of some distantly related and potentially terrestrial extinct crocodiles from Africa and South America,” said Mr. Ristevski. “We were quite surprised to find this, as Trilophosuchus rackhami evolutionarily is more closely related to today’s crocodiles. This may indicate that Trilophosuchus rackhami spent more time on land than most living crocodiles.”

Mr. Ristevski said the findings would be helpful in interpreting the evolutionary relationships of extinct crocodiles, something to be explored in the future.

Associate Professor Steve Salisbury said Australia had an astonishing diversity of prehistoric crocodiles until recently. “Trilophosuchus rackhami was definitely one of the cutest,” he said. “If we could travel back in time to northern Queensland 13 million years ago, not only would you have to watch out for crocodiles on the waterfront, but you’d also have to make sure you don’t step on them in the woods.”

The research was published in The anatomical record and The Journal of Anatomy.