An Aussie elaphrosaur younger than the rest

Australian palaeontologists have chanced upon an unusual toothless dinosaur that roamed the continent around 110 million years ago. 

That makes it the second youngest elaphrosaur known worldwide, they report in a paper in the journal Gondwana Research, and shows that elaphrosaurine theropods were capable of tolerating near-polar climates.

The story began in early 2015, when volunteer Jessica Parker unearthed a delicate five-centimetre bone during the annual dig at the Cretaceous-aged fossil site known as Eric the Red West, near Cape Otway, 225 kilometres southwest of Melbourne.

 It was identified at Melbourne Museum as a vertebra and thought to be from a flying reptile called a pterosaur. But when Stephen Poropat and Adele Pentland from Swinburne University of Technology attempted to work out exactly what type of pterosaur, things didn’t add up.

200520 vertebra
The vertebra found at Cape Otway. Credit: Stephen Poropat, Museums Victoria

“Pterosaur neck vertebrae are very distinctive”, says Pentland. “In all known pterosaurs, the body of the vertebra has a socket at the head end, and a ball or condyle at the body end. This vertebra had sockets at both ends, so it could not have been from a pterosaur.”

Pentland would know. She led the research team that just last year discovered a new species of pterosaur, Ferrodraco lentoni, in central Queensland, as reported in Cosmos.

After extensive research on Parker’s find, she and Poropat realised it was from a theropod: a meat-eating dinosaur, related to Tyrannosaurus rex and modern birds. Although, notes Poropat, it probably didn’t eat meat.

 The fossil is an excellent match for vertebrae from a strange group of theropods called elaphrosaurs – meaning nimble or light-footed lizards – although at just two metres it was rather small for an elaphrosaur and it lived at a different time to others.

 Its two main known relatives –Elaphrosaurus bambergi from Tanzania and Limusaurus inextricabilis from China – lived near the end of the Jurassic Period, 160-145 million years ago.

The new elaphrosaur dates to almost 40 million years later, and thus, the researchers write in their paper, “in tandem with the recently described Huinculsaurus montesi from the Cenomanian-Turonian of Argentina” it “implies that the spatiotemporal distribution of Elaphrosaurinae has heretofore been greatly underestimated”.

Poropat notes that “as dinosaurs go” elaphrosaurs were rather bizarre, with long necks, stumpy arms, small hands and relatively lightly built bodies.

 “The few known skulls of elaphrosaurs show that the youngsters had teeth, but that the adults lost their teeth and replaced them with a horny beak. 

“We don’t know if this is true for the Victorian elaphrosaur yet, but we might find out if we ever discover a skull.”

The team plans to return to the Eric the Red West site once COVID-19 restrictions permit.

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