New ‘apex predator’ dinosaur fossil unearthed with remains of crocodile prey still in mouth

A new “apex predator” dinosaur species has been discovered based on its fossil, unearthed in Argentina with a crocodile bone stuck in its jaws.

The species has been named Joaquinraptor casali, and was seven metres long, weighing over 1,000kg, researchers say.

It was a top predator in South America around 70 million years ago, and part of a family of “megaraptor” dinosaurs with powerful arms and claws.

These dinosaurs dominated South America, Asia and Australia, but knowledge about them has been hindered by the lack of complete fossils.

“Many important aspects of megaraptoran morphology and evolution remain poorly understood, due in large part to the fragmentary nature of most fossils of these theropods,” scientists wrote in a new study published in the journal Nature Communications.

The latest research describes a well-preserved and partially articulated remains of Joaquinraptor casali, named so as a “tribute to the son of the study’s first author” Lucio M Ibiricu, as well as the locality “Valle Joaquín” from which the fossil was recovered.

Researchers uncovered much of the fossil dinosaur’s skull, fore and hind limbs, ribs and vertebrae from the region also known as the Lago Colhué Huapi fossil site in Patagonia, Argentina.

“Here we report a previously unknown megaraptoran genus and species represented by a partially articulated partial skeleton recovered from an uppermost Cretaceous stratum of the Lago Colhué Huapi Formation of south-central Chubut Province in central Patagonia, Argentina,” researchers wrote.

The adult dinosaur specimen dates to the late Cretaceous era of about 70 million years ago, making it one of the most recently surviving types of megaraptorans, according to scientists.

However, the dinosaur appears not fully grown, and was likely 19 years old at death, they say.

Based on sediments found along with the dinosaur fossil, researchers suspect it lived in a warm, humid floodplain environment.

A fossilised crocodile leg bone was also found pressed against the lower jaws of J. casali, hinting at its feeding behaviour and suggesting the dinosaur may have been an apex predator in the region.

The dinosaur and its other megaraptor cousins were dominant predators in this region of South America before going extinct at the end of the Cretaceous with other non-avian dinosaurs, scientists say.

“Megaraptorids appear to have been the apex predators in central and southern Patagonian palaeoecosystems approaching the end of the Cretaceous,” they wrote.

However, researchers call for more research to provide further insights into its behaviour and ecological role.