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Pittman M.,University of Hong Kong | Pei R.,University of Hong Kong | Tan Q.,Long Hao Institute of Geology and Paleontology | Xu X.,CAS Institute of Vertebrate Paleontology and Paleoanthropology
PeerJ | Year: 2015

The first dromaeosaurid theropod from the Lower Cretaceous Bayan Gobi Formation is identified based on an incompletely preserved partially-articulated left leg, increasing the known diversity of its understudied ecosystem. The leg belongs to specimen IVPP V22530 and includes a typical deinonychosaurian pedal phalanx II-2 with a distinct constriction between the enlarged proximal end and the distal condyle as well as a typical deinonychosaurian enlarged pedal phalanx II-3. It possesses a symmetric metatarsus and a slender and long MT V that together suggest it is a dromaeosaurid. Two anatomical traits suggest the leg is microraptorine-like, but a more precise taxonomic referral was not possible: metatarsals II, III and IV are closely appressed distally and the ventral margin of the medial ligament pit of phalanx II-2 is close to the centre of the rounded distal condyle. This taxonomic status invites future efforts to discover additional specimens at the study locality because-whether it is a microraptorine or a close relative-this animal is expected to make important contributions to our understanding of dromaeosaurid evolution and biology. IVPP V22530 also comprises of an isolated dromaeosaurid manual ungual, a proximal portion of a right theropod anterior dorsal rib and an indeterminate bone mass that includes a collection of ribs. Neither the rib fragment nor the bone mass can be confidently referred to Dromaeosauridae, although they may very well belong to the same individual to whomthe left leg belongs. © 2015 Pittman et al. Source


Sereno P.C.,University of Chicago | Xijin Z.,CAS Institute of Vertebrate Paleontology and Paleoanthropology | Lin T.,Long Hao Institute of Geology and Paleontology
Proceedings of the Royal Society B: Biological Sciences | Year: 2010

We describe a new species of psittacosaur, Psittacosaurus gobiensis, from the Lower Cretaceous of Inner Mongolia and outline a hypothesis of chewing function in psittacosaurs that in many respects parallels that in psittaciform birds. Cranial features that accommodate increased bite force in psittacosaurs include an akinetic skull (both cranium and lower jaws) and differentiation of adductor muscle attachments comparable to that in psittaciform birds. These and other features, along with the presence of numerous large gastroliths, suggest that psittacosaurs may have had a high-fibre, nucivorous (nut-eating) diet. Psittacosaurs, alone among ornithischians, generate oblique wear facets from tooth-to-tooth occlusion without kinesis in either the upper or lower jaws. This is accomplished with a novel isognathous jaw mechanism that combines aspects of arcilineal (vertical) and propalinal (horizontal) jaw movement. Here termed clinolineal (inclined) jaw movement, the mechanism uses posteriorly divergent tooth rows, rather than kinesis, to gain the added width for oblique occlusion. As the lower tooth rows are drawn posterodorsally into occlusion, the increasing width between the upper tooth rows accommodates oblique shear. With this jaw mechanism, psittacosaurs were able to maintain oblique shearing occlusion in an akinetic skull designed to resist high bite forces. © 2009 The Royal Society. Source


Hone D.,CAS Institute of Vertebrate Paleontology and Paleoanthropology | Choiniere J.,George Washington University | Sullivan C.,CAS Institute of Vertebrate Paleontology and Paleoanthropology | Xu X.,CAS Institute of Vertebrate Paleontology and Paleoanthropology | And 2 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2010

Reconstructing the palaeoecology of extinct tetrapods is fraught with difficulties. Fossilized evidence of direct trophic interactions between tetrapods is rare, whether the interactions involve predation or scavenging. Typically this evidence is limited to preserved stomach contents or bite marks on bones (when they can be confidently attributed to specific taxa) that make it possible to begin to piece together the trophic webs that existed in ancient ecosystems. The dramatic 'fighting dinosaurs' fossil of a Velociraptor preserved in combat with a Protoceratops provides an outstanding, but still lone, example of the two taxa interacting. Here new evidence of a Velociraptor feeding on the carcass of a Protoceratops is presented, based on tooth-marked bones of the latter that were found in association with shed teeth of the former in Upper Cretaceous deposits at Bayan Mandahu, Inner Mongolia, China. In contrast to the case of the fighting dinosaurs, which seems to represent active predation by a Velociraptor, the tooth marks on the Bayan Mandahu material are inferred to have been produced during late-stage carcass consumption either during scavenging or following a group kill. Feeding by Velociraptor upon Protoceratops was probably a relatively common occurrence. © 2010 Elsevier B.V. All rights reserved. Source


Xu X.,CAS Institute of Vertebrate Paleontology and Paleoanthropology | Choiniere J.N.,George Washington University | Pittman M.,University College London | Tan Q.,Long Hao Institute of Geology and Paleontology | And 7 more authors.
Zootaxa | Year: 2010

We describe a new dromaeosaurid theropod from the Upper Cretaceous Wulansuhai Formation of Bayan Mandahu, Inner Mongolia. The new taxon, Linheraptor exquisitus gen. et sp. nov., is based on an exceptionally well-preserved, nearly complete skeleton. This specimen represents the fifth dromaeosaurid taxon recovered from the Upper Cretaceous Djadokhta Formation and its laterally equivalent strata, which include the Wulansuhai Formation, and adds to the known diversity of Late Cretaceous dromaeosaurids. Linheraptor exquisitus closely resembles the recently reported Tsaagan mangas. Uniquely among dromaeosaurids, the two taxa share a large, anteriorly located maxillary fenestra and a contact between the jugal and the squamosal that excludes the postorbital from the infratemporal fenestra. These features suggest a sister-taxon relationship between L. exquisitus and T. mangas, which indicates the presence of a unique dromaeosaurid lineage in the Late Cretaceous of Asia. A number of cranial and dental features seen in L. exquisitus and T. mangas, and particularly some postcranial features of L. exquisitus, suggest that these two taxa are probably intermediate in systematic position between known basal and derived dromaeosaurids. The discovery of Linheraptor exquisitus is thus important for understanding the evolution of some salient features seen in the derived dromaeosaurids. Copyright © 2010 Magnolia Press. Source


Xu X.,CAS Institute of Vertebrate Paleontology and Paleoanthropology | Upchurch P.,University College London | Ma Q.,CAS Institute of Vertebrate Paleontology and Paleoanthropology | Pittman M.,University College London | And 7 more authors.
Acta Palaeontologica Polonica | Year: 2013

The alvarezsauroid theropod Linhenykus monodactylus from the Upper Cretaceous of Inner Mongolia, China is the first known monodactyl non-avian dinosaur, providing important information on the complex patterns of manual evolution seen in alvarezsauroids. Here we provide a detailed description of the osteology of this taxon. Linhenykus shows a number of features that are transitional between parvicursorine and non-parvicursorine alvarezsauroids, but detailed comparisons also reveal that some characters had a more complex distribution. We also use event-based tree-fitting to perform a quantitative analysis of alvarezsauroid biogeography incorporating several recently discovered taxa. The results suggest that there is no statistical support for previous biogeographic hypotheses that favour pure vicariance or pure dispersal scenarios as explanations for the distributions of alvarezsauroids across South America, North America and Asia. Instead, statistically significant biogeographic reconstructions suggest a dominant role for sympatric (or "within area") events, combined with a mix of vicariance, dispersal and regional extinction. At present the alvarezsauroid data set is too small to completely resolve the biogeographic history of this group: future studies will need to create larger data sets that encompass additional clades. Copyright © 2012. Source

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