411 research outputs found

    Anatomy of Mahakala omnogovae (Theropoda: Dromaeosauridae), Tögrögiin Shiree, Mongolia

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    The dromaeosaurid Mahakala omnogovae is known from a unique specimen from the late Cretaceous deposits of the Djadokhta Formation at Tögrögiin Shiree, Ömnögov Aimag, Mongolia. The holotype specimen is comprised of a well-preserved but partial skull and a nearly complete postcranial skeleton. Mahakala omnogovae is included in a comprehensive phylogenetic analysis of Coelurosauria using a dataset, which reflects a greatly expanded character set and taxon-sampling regime. Several interesting features of Mahakala omnogovae have implications for deinonychosaurian and avialan character evolution and for understanding patterns of size variation and size change within paravian theropods. These morphologies include the shape of the iliac blade, the triangular obturator process of the ischium, and the evolution of the subarctometatarsalian condition. We present an expanded diagnosis of Mahakala omnogovae which included following unique combination of characters (autapomorphies noted by *): a ledgelike depression at the confluence of metotic strut and posterior tympanic recess on the anterior face of the paroccipital process*, a posteriorly tapering scapula; a shortened forelimb (humerus 50% femur length); a strongly compressed and anteroposteriorly broad ulna tapering posteriorly to a narrow edge*; elongate lateral crest on the posterodistal femur*; anterior caudal vertebrae with subhorizontal, laterally directed prezygapophyses*; a prominent supratrochanteric process; and the absence of a cuppedicus fossa.Fil: Turner, Alan Hamilton. State University Of New York. Stony Brook University. Departament Of Philosophy; Estados Unidos. American Museum of Natural History; Estados UnidosFil: Pol, Diego. Museo Paleontológico Egidio Feruglio; Argentina. American Museum of Natural History; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Norell, Mark A.. American Museum of Natural History; Estados Unido

    THE OSTEOLOGY OF ALIORAMUS, A GRACILE AND LONG-SNOUTED TYRANNOSAURID (DINOSAURIA: THEROPODA) FROM THE LATE CRETACEOUS OF MONGOLIA

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    Fig. 68: Closeup of right ilium of the holotype specimen of Alioramus altai (IGM 100/1844) in lateral view. Scale bar 5 5 cm. Abbreviations as in figure 66.Published as part of Brusatte, Stephen L., Carr, Thomas D. & Norell, Mark A., 2012, The Osteology Of Alioramus, A Gracile And Long-Snouted Tyrannosaurid (Dinosauria: Theropoda) From The Late Cretaceous Of Mongolia, pp. 1-197 in Bulletin of the American Museum of Natural History 2012 (366) on page 149, DOI: 10.1206/770.1, http://zenodo.org/record/539926

    Ornithischian dinosaur Haya griva.

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    19 pages : illustrations (some color), 1 color map ; 26 cm.Although Mesozoic fossils are quite common in the Gobi Desert of Central Asia, it is often difficult to correlate among different localities because of a dearth of rocks amenable to absolute dating. Specifically, correlating between the eastern Gobi Desert and more western localities has been challenging. Here we give a Santonian-Campanian age for the enigmatic Zos Canyon beds in the Nemegt basin. This is based on the occurrence of the primitive ornithopod dinosaur Haya griva at both eastern Gobi exposures of the Javkhlant Formation and the Zos Canyon locality

    New Specimens of Microraptor zhaoianus (Theropoda: Dromaeosauridae) from Northeastern China

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    New material of Erketu ellisoni.

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    27 p. : ill. ; 26 cm. "October 22, 2010."Phylogenetic relationships among the diverse Cretaceous sauropods of East Asia have long been controversial. Debate has centered on whether there is any evidence for an endemic clade of Asian species ("Euhelopodidae") and on the placement of these taxa within the context of higher sauropod phylogeny. While most Cretaceous sauropod taxa from Asia are recognized as part of Somphospondyli, recent discoveries have suggested Brachiosauridae may have dispersed into Asia as well. We present new fossils and analyses bearing on these issues. Additional material of the holotype individual of Erketu ellisoni recovered on a subsequent visit to the type locality expands the character data available for this unique sauropod. Associated sauropod dorsal and caudal vertebrae were collected from the same horizon, at a location approximately 2 km from the holotype excavation. The dorsal vertebra exhibits synapomorphies suggesting a representative of Titanosauria co-occurred with Erketu ellisoni. These new specimens, as well as recent discoveries of contemporary Asian sauropod taxa, allow a basis for phylogenetic reappraisal of Erketu and related taxa. Phylogenetic results support a sister group relationship between the Asian Cretaceous sauropods Erketu and Qiaowanlong. Although Qiaowanlong was described as a brachiosaurid, it joins Erketu on the somphospondylian side of the Brachiosauridae-Somphospondyli divergence, erasing the evidence for the dispersal of Brachiosauridae into Asia

    Late Cretaceous turtle.

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    19 p. : ill. ; 26 cm.Includes bibliographical references (p. 15-16).The late Cretaceous continental deposits of Ukhaa Tolgod, Mongolia, have yielded remains of a new nanhsiungchelyid turtle, Zangerlia ukhaachelys, n.sp. This taxon is based on a single individual that consists of a partial cranium, representatives of all peripherals, an almost complete plastron, and limb fragments. Zangerlia ukhaachelys is diagnosed as a new taxon by the presence of an anteromedial process of the hyoplastron that reduces the typical contact of the entoplastron with the epiplastron. Phylogenetic analysis firmly places Zangerlia ukhaachelys as sister to Zangerlia testudinimorpha and Zangerlia neimongolensis within Nanhsiungchelyidae and confirms the close phylogenetic relationships between Nanhsiungchelys wuchingensis and Anomalochelys angulata and among all North American representatives of Basilemys. In addition, there is modest support that all Asian representatives of Nanhsiungchelyidae form a monophyletic clade, which is primarily diagnosed by a deep, triangular nuchal notch. From a biogeographic standpoint, it is evident that the late Cretaceous faunas of Asia and North America are closely related; however, phylogenetic considerations demonstrate that faunal exchange was limited for the Nanhsiungchelyidae

    A neoceratopsian dinosaur from the early Cretaceous of Mongolia and the early evolution of ceratopsia

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    Ceratopsia is a diverse dinosaur clade from the Middle Jurassic to Late Cretaceous with early diversification in East Asia. However, the phylogeny of basal ceratopsians remains unclear. Here we report a new basal neoceratopsian dinosaur Beg tse based on a partial skull from Baruunbayan, Ömnögovi aimag, Mongolia. Beg is diagnosed by a unique combination of primitive and derived characters including a primitively deep premaxilla with four premaxillary teeth, a trapezoidal antorbital fossa with a poorly delineated anterior margin, very short dentary with an expanded and shallow groove on lateral surface, the derived presence of a robust jugal having a foramen on its anteromedial surface, and five equally spaced tubercles on the lateral ridge of the surangular. This is to our knowledge the earliest known occurrence of basal neoceratopsian in Mongolia, where this group was previously only known from Late Cretaceous strata. Phylogenetic analysis indicates that it is sister to all other neoceratopsian dinosaurs

    Khaan mckennai.

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    77 p. : ill. (some col.) ; 26 cm.The monophyly of Oviraptoridae, a group of theropod dinosaurs, which share a uniquely bizarre morphology, has never been called into question due in large part to their unusual complex of characters. Despite a vivid recent history of discovery and broad public appeal the nature of their morphological diversity has not been explored extensively. Many previous descriptions of oviraptorid taxa are lost in the obscurity of hard-to-find journals, and many lack illustrations of what are now recognized as phylogenetically important characters. The primary goal of this paper is to provide a relatively comprehensive descriptive morphology and illustrations for one member of Oviraptoridae, namely Khaan mckennai, with an emphasis on characters that can be used to establish a phylogenetic hypothesis for the taxon and group as a whole. K. mckennai is a small-bodied, crestless oviraptorid that is known from pristine material that has been collected from the late Cretaceous sediments of Mongolia. Similar to other oviraptorids, it shares a wide number of features in common with extant birds. However, when these characters are put in the context of Oviraptorosauria, including relatively new, more basal forms like Incisivosaurus gauthieri and Caudipteryx zoui, character states such as extreme pneumatization of the skull or the reduction in the number of caudal vertebrae are found to be either homoplastic for the two groups or plesiomorphic for a more inclusive clade

    Gilmoreosaurus mongoliensis.

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    49 p. : ill. ; 26 cm. "August 23, 2010." "The first fossil remains of Gilmoreosaurus mongoliensis were collected in 1923 by George Olsen during the Central Asiatic Expeditions of the American Museum of Natural History ... from two quarries ... in the Upper Cretaceous Iren Dabasu Formation, Inner Mongolia, northern China"--P. 2.The osteology of the hadrosauroid dinosaur Gilmoreosaurus mongoliensis is redescribed in detail based on the disarticulated cranial and postcranial elements of at least four individuals. These together constitute the lectotype and hypodigm of this species. The diagnosis is emended to include two autapomorphies (paddle-shaped postacetabular process that is less than 70% of the length of the iliac central plate and manual phalanx III-1 with greatly asymmetrical distal surface) and the unique combination of two iliac characters (presence of ischial tuberosity and supraacetabular process with apex located posterodorsal to ischial peduncle). The distinction of G. mongoliensis from B. johnsoni is confirmed on the basis of characters of the maxilla, dentition, ilium, ischium, and pubis. Maximum parsimony analysis places G. mongoliensis as a closely related outgroup to the Hadrosauridae, the sister taxon to the clade composed of all hadrosauroids closer to Telmatosaurus transsylvanicus than to Bactrosaurus johnsoni

    A catalogue of Zalmoxes (Dinosauria: Ornithopoda) specimens from the Upper Cretaceous Nălaț-Vad locality, Haţeg Basin, Romania

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    FIGURE 11. Partial right proximal scapula of Zalmoxes shqiperorum LPB (FGGUB) R.2403 in A, lateral, B, medial, C, dorsal, D, ventral and E, proximal views. Abbreviations: acr, acromion; af, anterior fossa; ha, humeral articulation; scn, scapular neck.Published as part of Brusatte, Stephen L., Dumbravă, Mihai, Vremir, Mátyás, Csiki-Sava, Zoltán, Totoianu, Radu & Norell, Mark A., 2017, A catalog of Zalmoxes (Dinosauria: Ornithopoda) specimens from the Upper Cretaceous Nălaț-Vad locality, Haţeg Basin, Romania, pp. 1-36 in American Museum Novitates 2017 (3884) on page 19, DOI: 10.1206/3884.1, http://zenodo.org/record/456621
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