One locality that has been producing a number of new theropod species recently are the rocks of the Neuquén Group in Patagonia. The Neuquén Group spans some twenty million years of the Cretaceous, from approximately 100 million years ago to 80 million years ago. In July of 2016, paleontologists Rodolfo Coria and Phil Currie described a new theropod from the Sierra Barrosa Formation, a unit of rocks within the Neuquén Group, laid down approximately 90 million years ago.
The new theropod, named Murusraptor barrosaensis, was discovered near the town of Plaza Huincul, in Neuquén Province, Argentina. The specimen was discovered in the wall of a ravine cut into sandstones deposited by an ancient river. Although it’s incompletely known, the total length of the animal is estimated to be approximately 7.5 meters, with a hip height of about two meters. The name Murusraptor is derived from the Latin words murus meaning wall and raptor mean robber, a reference to the site of discovery. The specific name, barrosaensis, refers to the Sierra Barrosa Formation.
Murusraptor is known from a skull preserving the rear part of the cranium and mandible, some vertebrae and ribs, gastralia (sometimes called belly ribs), a single claw from the hand, and a partial pelvis and hindlimbs. Although the skull is incompletely known, it shows that Murusraptor had a long, low snout, and lacked any kind of ornamentation around the eyes. This is quite different from many theropods of similar size like Allosaurus and Ceratosaurus that had prominent “eyebrow” crests. The teeth of Murusraptor are also unique, being unusually small for an animal of its size; the largest tooth recovered is less than three centimeters tall! The vertebrae, ribs, and pelvic bones show extensive pneumatization, meaning that bones are invaded by complex outgrowths of lung tissue called air sacs. Skeletal pneumatization is common in theropods as well as pterosaurs.