Abstract
Dromaeosaurids (Theropoda: Dromaeosauridae), a group of dynamic, swift predators, have a sparse fossil record, particularly at the time of their extinction near the Cretaceous-Paleogene boundary. Here we report on a new dromaeosaurid, Dineobellator notohesperus, gen. and sp. nov., consisting of a partial skeleton from the Upper Cretaceous (Maastrichtian) of New Mexico, the first diagnostic dromaeosaurid to be recovered from the latest Cretaceous of the southern United States (southern Laramidia). The holotype includes elements of the skull, axial, and appendicular skeleton. The specimen reveals a host of morphologies that shed light on new behavioral attributes for these feathered dinosaurs. Unique features on its forelimbs suggest greater strength capabilities in flexion than the normal dromaeosaurid condition, in conjunction with a relatively tighter grip strength in the manual claws. Aspects of the caudal vertebrae suggest greater movement near the tail base, aiding in agility and predation. Phylogenetic analysis places Dineobellator within Velociraptorinae. Its phylogenetic position, along with that of other Maastrichtian taxa (Acheroraptor and Dakotaraptor), suggests dromaeosaurids were still diversifying at the end of the Cretaceous. Furthermore, its recovery as a second North American Maastrichtian velociraptorine suggests vicariance of North American velociraptorines after a dispersal event during the Campanian-Maastrichtian from Asia. Features of Dineobellator also imply that dromaeosaurids were active predators that occupied discrete ecological niches while living in the shadow of Tyrannosaurus rex, until the end of the dinosaurs’ reign.
Highlights
Dromaeosaurids (Theropoda: Dromaeosauridae) have been found in North America from the Early to Late Cretaceous, from as far west as Alaska to as far east as Maryland[1,2,3]
We report on a new dromaeosaurid dinosaur, Dineobellator notohesperus, gen. and sp. nov., discovered in 2008, and briefly mentioned by Jasinski et al.[15], from the Naashoibito Member (Ojo Alamo Formation), San Juan Basin, New Mexico
The deltopectoral crest is relatively larger in Dineobellator [estimated 31% of total humeral length in Dineobellator compared to other dromaeosaurids with preserved humeri (e.g., 20.5% in Bambiraptor feinborgorum, 23.5% in Dakotaraptor steini, 25% in Saurornitholestes langstoni, and 28% in Deinonychus antirrhopus)]
Summary
Dromaeosaurids (Theropoda: Dromaeosauridae) have been found in North America from the Early to Late Cretaceous, from as far west as Alaska to as far east as Maryland[1,2,3]. The holotype specimen, SMP VP-2430 (Vertebrate Paleontology Collection, State Museum of Pennsylvania, Harrisburg, Pennsylvania, USA), consists of at least 20 identifiable skeletal elements, including parts of the skull, fore- and hindlimbs, and axial skeleton. These skeletal remains are complete enough to compare to other known dromaeosaurids, assess its phylogenetic position, and infer additional aspects of their life history and predatory behavior. James Nikas in 2008, and more material was subsequently collected from the same individual by Sullivan and Jasinski in 2009 and Jasinski in 2015 and 2016
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