The osteology of Alioramus, a gracile and long-snouted tyrannosaurid (Dinosauria, Theropoda) from the late Cretaceous of Mongolia. (Bulletin of the American Museum of Natural History, no. 366)

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dc.contributor.author Brusatte, Stephen.
dc.contributor.author Carr, Thomas D.
dc.contributor.author Norell, Mark.
dc.contributor.author Mongolian-American Museum Paleontological Project.
dc.contributor.author Mongolyn Shinzhlėkh Ukhaany Akademi.
dc.date.accessioned 2012-03-02T21:34:38Z
dc.date.available 2012-03-02T21:34:38Z
dc.date.issued 2012-02-29
dc.identifier.uri http://hdl.handle.net/2246/6162
dc.description 197 p. : ill. (some col.) ; 26 cm. en_US
dc.description.abstract The late Cretaceous tyrannosaurid theropod Alioramus has long been one of the most puzzling large carnivorous dinosaur taxa, largely because for several decades it has been represented only by a single, fragmentary specimen that seems to represent a long-snouted and gracile individual but is difficult to interpret. The discovery of a substantially complete skeleton of Alioramus at the Tsaagan Khuushu locality in the Maastrichtian Nemegt Formation of Mongolia, recovered during the 2001 American Museum-Mongolian Academy of Sciences expedition and described as a new species (Alioramus altai) in 2009, definitively shows that this mysterious taxon is a distinct form of longirostrine tyrannosaurid that lived alongside the larger and more robust Tarbosaurus. Here we describe and figure this remarkably preserved skeleton in detail. We provide exhaustive descriptions and photographs of individual bones, and make extensive comparisons with other tyrannosauroids. This monographic description provides further evidence that Alioramus is an unusual long-snouted, gracile, and slender-limbed taxon with an unprecedented degree of cranial ornamentation among tyrannosaurids and an extremely pneumatized skeleton. Anatomical comparisons indicate that the long skull of Alioramus is an autapomorphic feature that is proportionally longer (relative to femur length) than in any other known tyrannosaurid specimen, including juveniles, and that Alioramus is morphologically distinctive relative to similarly sized individuals of the contemporary and sympatric Tarbosaurus. The holotype specimen of A. altai belongs to a young individual, and many differences between it and the other known specimen of Alioramus (the holotype of A. remotus) may represent ontogenetic variation. The unusual longirostrine skull of Alioramus was largely produced by lengthening of the snout bones (maxilla, nasal, dentary, lacrimal, jugal), rather than the orbiotemporal bones (frontal, postorbital, squamosal, quadratojugal). The long snout, gracile skull bones, comparatively small attachment sites for jaw muscles, and lack of interlocking sutures and a robust orbital brow would have precluded the holotype individual from employing the characteristic "puncture-pull" feeding style of large-bodied adult tyrannosaurids, in which the muscular jaws, thick teeth, and interlocking sutures enabled individuals to bite with enough force to fracture bone. Whether adult Alioramus could utilize "puncture-pull" feeding awaits discovery of mature individuals of the genus. The coexistence of the long-snouted Alioramus and robust and deep-snouted Tarbosaurus, which are found together at the Tsaagan Khuushu locality, demonstrate that multiple large tyrannosaurids were able to live in sympatry, likely because of niche partitioning due to differences in craniofacial morphology and functional behavior. en_US
dc.language.iso en_US en_US
dc.publisher American Museum of Natural History. en_US
dc.relation.ispartofseries Bulletin of the American Museum of Natural History, no. 366. en_US
dc.subject Alioramus altai. en_US
dc.subject Alioramus. en_US
dc.subject Tyrannosauridae. en_US
dc.subject Dinosaurs. en_US
dc.subject Skull. en_US
dc.subject Ȯmnȯgovʹ Aĭmag (Mongolia) en_US
dc.subject Mongolia. en_US
dc.title The osteology of Alioramus, a gracile and long-snouted tyrannosaurid (Dinosauria, Theropoda) from the late Cretaceous of Mongolia. (Bulletin of the American Museum of Natural History, no. 366) en_US
dc.title.alternative Osteology of tyrannosaurid Alioramus. en_US

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  • Bulletin of the American Museum of Natural History
    The Bulletin, published continuously since 1881, consists of longer monographic volumes in the field of natural sciences relating to zoology, paleontology, and geology. Current numbers are published at irregular intervals. The Bulletin was originally a place to publish short papers, while longer works appeared in the Memoirs. However, in the 1920s, the Memoirs ceased and the Bulletin series began publishing longer papers. A new series, the Novitates , published short papers describing new forms.

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