Paleontologists Have Found New ‘Megaraptor’ Dinosaur

Murusraptor barrosaensis lived about 80 million years ago in what is now Patagonia.

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Jul 20 2016, 6:00pm

Image: Jan Sovak

Paleontologists have discovered a new species of "megaraptor," a type of carnivorous dinosaur every bit as badass as it sounds. Found in fossil-rich Patagonia, at the tip of South America, the latest addition to the megaraptor clade has been dubbed Murusraptor barrosaensis. The stealthy predator measured about 6.5 meters long and lived approximately 80 million years ago in the rich, mysterious landscape of late Cretaceous Argentina.

"We know very little about the Murusraptor's ecosystem," Rodolfo Coria, a paleontologist based at Argentina's Consejo Nacional de Investigaciones Científicas y Técnicas, told me via email. Together with fellow paleontologist Philip Currie of the University of Alberta, Coria is the senior author of a detailed description of the new species, published Wednesday in the open-access journal PLOS ONE.

"From the same geological formation, we have collected some remains of large long-necked dinosaurs (sauropods) and isolated petrified wood of pine-trees," he continued. "Apparently, the area was inhabited by a diversified fauna with different dinosaur types, crocodiles, turtles, and small mammals. We think that Murusraptor was an active predator and its preys were an assemblage of the mentioned vertebrates."

Diagram showing the partial skeleton of Murusraptor barrosaensis. Image: Coria, Currie, et al (2016)

The holotype specimen of M. barrosaensis shows visible sutures in its bony braincase, indicating that the animal was likely a juvenile when it died, with a skull that only had just settled into its adult shape. But even as an adolescent, the carnivore was still comparable in size to other megaraptor species found in Argentina, like Aerosteon or Orkoraptor.

Despite the "raptor" branding of these animals, megaraptors were not the true raptors (or "dromaeosaurids") depicted opening doors and taunting children in Jurassic Park.

That said, what these predators actually were is a matter of substantial debate among paleontologists. One camp has proposed that megaraptors are the last surviving members of the once-ubiquitous Allosaurus clan, which would upend existing theories about this group's extinction. Another has suggested that these idiosyncratic meat-eaters were coelurosaurs, making them more closely related to tyrannosaurs.

Confusing matters further is the range of features observed in megaraptors, some of which seem to resemble spinosaurs like Baryonyx; others hinting at a megalosauroid heritage.

Coria hopes that future studies on Murusraptor and its kin will finally solve the mystery of the megaraptor family tree. "Our current strategy includes two ways to get into this problem," he told me. "One way to get close to the solution of this controversy is to review all different species and build a whole new data set, avoiding biases and preconcepts."

The canyon wall where the new species was found. Image: Coria/Currie

The second, according to Coria, is "to explore older rocks, eventually Lower Cretaceous or Upper Jurassic to find for ancestral forms of megaraptors. I am currently studying new specimens from Early Cretaceous rocks, which I hope could be useful for these goals."

"This is a super cool specimen from a very enigmatic family of big dinosaurs," said Currie in a statement. "Because we have most of the skeleton in a single entity, it really helps consolidate their relationships to other animals."

Whatever their heritage, megaraptors like Murusraptor were clearly skilled hunters back in the Cretaceous day, eking out an ecological niche distinct from heavyweights like T. rex or small sleek hunters like Velociraptor. Mid-sized theropods deserve love too.