Pint-sized but with a Nasty Bite – Eodromaeus from the Triassic of Argentina

It may have been small, but it was quick, agile and had a nasty bite, researchers have announced the discovery of a new genus of dinosaur from Argentina.  The dinosaur has been formally named and described – Eodromaeus murphi and it was a basal Theropod, an ancestor of ferocious dinosaurs such as Giganotosaurus, Allosaurus and Tyrannosaurus rex.

South America is regarded as the “cradle of dinosaur evolution”, with a number of primitive dinosaurs known from Argentina, in particular the mid Triassic strata of the Ischigualasto Formation in an area known as the Valley of the Moon.  This new Theropod, known from two specimens that were found in close proximity to each other, measured approximately 1.2 metres in length (mostly tail), it would have weighed around 5 kilogrammes.

The paper on this dinosaur has been published in the scientific journal “Science”.

An Illustration of Eodromaeus murphi

Picture Credit: Todd Marshall

The dinosaur’s name means “dawn runner” and it is one of a number of basal Theropods known from the Valley of the Moon area, other Theropods such as Herrerasaurus and Eoraptor, although dinosaurs were not the most common animals in the area, there were many different types of reptile and many of them were much, much bigger than the dinosaurs.

Commenting on the new dinosaur discovery, Paul Sereno of the University of Chicago, a palaeontologist who has worked extensively in Argentina stated:

“It was very cute, you would want it as a pet.  But it might be best as a guard dinosaur, to keep the dogs away.”

The fossilised bones of Eodromaeus have been dated to approximately 224 million years ago (late Carnian faunal stage).  Unlike Herrerasaurus, this dinosaur had hands that had three-clawed fingers.  It was very likely a fast runner and the narrow skull had some enlarged, sharply curved teeth at the front of the jaws.

Eodromaeus superficially resembles Eoraptor in size and anatomical structure, but scientists now believe that Eoraptor was an ancestor of the long-necked Sauropods.  The basal ancestry of the Sauropods remains unclear but recently, a discovery of a primitive quadruped from Argentina may have provided vital clues as to the evolution of the Sauropoda.

To read more about this discovery: The Mother of All Sauropods

As both genera were small, ran on two legs and lived around the same time, researchers believe that the common ancestor of all dinosaurs was also just about four feet in length and originated in South America.

Paul Sereno added:

“This gives us the earliest snapshot of dinosaurs.  They were just a couple of million years away from the ultimate ancestor.”

A Reconstruction of the Eodromaeus Skeleton

Eodromaeus skeleton

Picture Credit: Mike Hettwer

The long shin bones and large metatarsals indicate an agile, speedy runner.  The long tail would have helped this little dinosaur to balance and change direction quickly.  Although a carnivore, Eodromaeus was not top of the food chain, there were plenty of predatory mammal-like reptiles and carnivorous Rauisuchids that would have made short work of Eodromaeus had they been able to catch one.

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