 |
| Dineobellator notohesperus
Jasinski, Sullivan & Dodson, 2020
Illustration: Sergey Krasovskiy
|
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.
 |
| Figure 1: Selected elements and features of the holotype of Dineobellator notohesperus (SMP VP-2430), gen. et sp. nov., including: right humerus, posterior (A) view; right ulna, medial (B) view; close up of ulna showing feathers where ulnar papillae are located along the ulnar ridge, feathers used are from Megascops kennicottii (C); middle caudal vertebra (D,E), distal (D) and (E) lateroventral (E) views, with red highlighting circular indent on centrum surface; tooth, lateral (F) view; magnification of distal basal denticles (G); anterior caudal vertebra 1, right lateral (H) view; right manual ungual II (I–L), lateral (I) view, silhouette of transverse plane of right manual ungual II near distal end (J), medial (K) view, and with area shown in dashed box in K highlighting abnormal oblong concavity in red (L); right pedal ungual III, partially reconstructed, lateral (M) view.
Abbreviations: cc, central concavity; dc, deltopectoral crest; eg, digital extensor groove; ft, flexor tubercle; ld, latissimus dorsi scar; lg, lateral groove; mc, medial crest; mg, medial groove; na, neural arch; ns, neural spine; op, olecranon process; tp, transverse process. Scale bars, 1 cm for (A–E) and (H–M), 1 mm for (F,G). (L) not to scale.
|
 |
| Figure 2: Skeletal reconstruction of Dineobellator notohesperus gen. et sp. nov., SMP VP-2430, with known elements colored in white. Figured bones are as follows: fused distal caudal vertebra (A); middle caudal vertebra (B); caudal vertebra 1 (C); right femur (D); rib (E); right basipterygoid (F); left lacrimal (reversed) (G); right jugal (H); right humerus (I); right ulna (J); right metacarpal III (K); right manual ungual II (L); right metatarsal II (M); right metatarsal III. (N) Individual scale bars, 2 cm. Skeletal drawing based off work of Scott Hartman. |
Systematic paleontology
Dinosauria Owen, 1842;
Theropoda Marsh, 1881;
Coelurosauria Huene, 1914;
Dromaeosauridae Matthew and Brown, 1922;
Dineobellator notohesperus gen. et sp. nov.
Etymology: The generic name is derived from Diné, the Navajo word in reference to the people of the Navajo Nation, and the Latin suffix bellator, meaning warrior. The specific epithet noto is from the Greek, meaning southern, or south; and the Greek hesper meaning western, in reference to the American Southwest. Additionally, Hesperus refers to a Greek god, namely the personification of the evening star and, by extension, “western.” Pronounced “dih NAY oh - BELL a tor” “Noh toh – hes per us.”
Holotype: SMP VP-2430 is a disarticulated, associated individual consisting of a rostromedial portion of right premaxilla, left maxilla fragment, ?maxillary tooth, dorsolateral process of left lacrimal, left ?nasal fragment, incomplete right jugal, incomplete right basipterygoid, incomplete occipital condyle, isolated prezygopophyses, isolated vertebral processes, caudal vertebra 1, middle caudal vertebra, four fused distal caudal vertebrae, several vertebral fragments, nearly complete rib and rib fragments, nearly complete right humerus, nearly complete right ulna, incomplete right metacarpal III, nearly complete right manual ungual II, incomplete right femur, incomplete right metatarsals I, II and III, incomplete left ?astragalus, nearly complete right pedal ungual III, and various other cranial and post-cranial bone fragments (Figs. 1–2). Portions of the specimen were first found and collected by Robert M. Sullivan, Steven E. Jasinski, and 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.
Type locality and horizon: The type locality, SMP 410b, Bisti/De-na-zin Wilderness, New Mexico. Precise locality information is on file at the State Museum of Pennsylvania, Section of Paleontology and Geology, and is available to qualified researchers. The holotype (SMP VP-2430) was collected within a few meters above the base of the Naashoibito Member (Ojo Alamo Formation) in relatively poorly consolidated sandstone. 40Ar/39Ar dates acquired from detrital sanidines give a maximum depositional age for the Naashoibito Member at 66.5 ± 0.2 Ma (upper Maastrichtian)16,17,18,19,20. Biostratigraphy, however, seems to suggest an early late Maastrichtian age, approximately 70.0–68.0 Ma21.
Diagnosis: A mid-sized dromaeosaurid theropod that differs from other eudromaeosaurs by the following characters: offset of lateral grooves on manual ungual; distinct and conspicuous dorsomedial groove proximally dorsal to the articular surface on the manual ungual; sharp angle of distal deltopectoral crest of the humerus; opisthocoelous proximal caudal vertebrae; short and robust neural spines on proximal caudal vertebrae; gracile and subrectangular transverse processes on proximal caudal vertebrae; proximal caudal vertebrae with curved ventral surface and oval to subrectangular cranial and caudal centrum surfaces; distinct round concavities on cranial and caudal centrum surfaces in mid-caudal vertebrae; enlarged flexor tubercles on manual ungual II and pedal ungual III; and secondary lateral grooves ventral on pedal unguals.
 |
| Figure 3: Time-calibrated phylogeny of dromaeosaurid relationships illustrating the major relationships within the family including their paleobiogeography. Strict consensus phylogenetic tree resulting in 32 most parsimonious trees, each with a tree length of 416 steps, a Consistency Index of 0.466, and a Retention Index of 0.640. Archaeopteryx is the outgroup. Temporal positions and biogeographic locations of dromaeosaurid taxa are provided. Silhouettes are taken from phylopic.org and are freely available for reuse under a Public Domain or Creative Commons license (www.phylopic.org), see SI for more information about individual silhouettes. Credits for silhouettes and references for temporal positions and biogeographic locations provided in SI. |
 |
| Dineobellator notohesperus from the Ojo Alamo Formation from the end of the Cretaceous period in New Mexico.
the ceratopsid Ojoceratops
A small tyrannosaurid is following the sauropod Alamosaurus
hadrosaurids and the rare caenagnathid oviraptorosaur Ojoraptorsaurus
Illustration: Sergey Krasovskiy
|
Steven E. Jasinski, Robert M. Sullivan and Peter Dodson. 2020. New Dromaeosaurid Dinosaur (Theropoda, Dromaeosauridae) from New Mexico and Biodiversity of Dromaeosaurids at the End of the Cretaceous. Scientific Reports. 10: 5105. DOI: 10.1038/s41598-020-61480-7
Scientists working in New Mexico found a fossilized 6-inch dinosaur claw that has led them to recognize a fierce new species, Dineobellator notohesperus
