An ancient species of crocodile discovered in central Australia
A new species of crocodile has been identified from fossil remains discovered in central Australia.
The 8 million-year-old skull of the now-extinct Baru genus was found at the Alcoota Fossil Site, 200km north-east of Alice Springs.
Unlike Australia’s modern crocodiles, which are believed to have migrated from Africa, crocodiles of the Baru genus were endemic to Australia.
That the skull is in such good condition means it will serve as the holotype for its species – a holotype is the specimen upon which a name is based and can be used as the standard reference for a species.
This Alcoota Baru is distinct from other species of Baru previously described from fossil remains found at a different site in the Northern Territory.
What we can learn from the ancient crocodile skull
Senior curator of earth sciences at the Museum and Art Gallery of the Northern Territory, Adam Yates, has been painstakingly working away at the skull since it was discovered in 2009.
“Working on the skull has been an extremely rewarding and satisfying experience,” he says.
“It is wonderful to see a skull slowly emerge over weeks and months, as I try and anticipate how exactly it is going to look.
“It is also a real honour to work with such a beautiful fossil – all too often fossil animals are broken into many separate parts that we have to use our skills to try and reconstruct. Having the entire skull in one piece for once was a joyous experience.
“I also love slowly getting to know the anatomy of the beast in fine detail as it is compared to fossil crocodiles including closely related ones of the same genus, slowly building a case that this is new and distinct.”
According to Adam, the most striking difference between the Alcoota Baru and Australia’s modern crocodiles is the missing interlocking dentition, where the upper and lower teeth mesh together when the jaw closes.
“Baru had an overbite with the upper teeth overhanging the lower teeth,” he says. “The great depth of the jaws and snout would have also been immediately obvious to an observer.”
The size and strength of the crocodile also suggests it went for big prey.
“It seems likely that Baru hunted megafauna, probably by ambushing them at the edge of rivers and lakes when the big animals came in for a drink.” This claim is supported by crocodile tooth marks on megafauna bones found at an older Northern Territory fossil site.
Ancient Australian crocodiles
Baru crocodiles belong to an ancient group known as Mekosuchinae, which first appear in the fossil record about 45 million years ago in Queensland.
“Early Mekosuchines were rather ordinary-looking crocodiles but as time went on they produced all sorts of unusual forms, including terrestrial hunters with slicing blade-shaped teeth, big robust deep-skulled aquatic ambush hunters of megafauna, giant flat-headed aquatic predators, and dwarf terrestrial forms with exceptionally short snouts that might have climbed trees.”
But this ancient group is entirely extinct. “Modern Australian crocodiles are not Mekosuchines, they are part of the genus Crocodylus, which had its origins on the African continent and entered Australia by ‘island-hopping’ through south-east Asia in the recent geological past.”
Adam is yet to name the new species, which is set to be finalised in 2022.