The osteology of Alioramus, a gracile and long-snouted tyrannosaurid (Dinosauria: Theropoda) from the late Cretaceous of Mongolia / Stephen L. Brusatte ; Thomas D. Carr ; Mark A. Norell

• Superior document: Bulletin of the American Museum of Natural History 366
• VerfasserIn: Brusatte, Steve 1984-; Carr, Thomas D.; Norell, Mark 1957-
• Place / Publishing House: New York, NY : American Museum of Natural History, 2012
• Year of Publication: 2012
• Language: English
• Series: Bulletin of the American Museum of Natural History 366
• Physical Description: 197 S.; zahlr. Ill.; 26 cm
• Notes: Literaturverz. S. 191 - 196

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. 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.