[N] 2006 A new arrangement of the palatal elements in Tyrannosaurus rex.
Holland, M. (2006) A new arrangement of the palatal elements in Tyrannosaurus rex. JVP 26(3) Abstracts pp.76
Previous descriptions of tyrannosaur palates place the posterior end of the vomer medial to and between the anterior pterygoid flanges. This vomeropterygoid complex is then positioned medial to and between the ascending processes of the palatines. This arrangement left an open space between the two posterior plates of the vomer. The recent assembly of two Tyrannosaurus rex skulls suggest a different arrangement of these palatal elements.
The larger skull MOR 008, was collected from the Hell Creek formation in Montana during the late 1960’s, and was mostly articulated upon discovery. Since then, it has existed as largely a collection of broken fragments. Upon reassembly the skull was found to be the largest Tyrannosaurus rex skull ever collected. The smaller skull, MOR 1125, also from the Hell Creek formation, was collected in 2002. This exceptionally preserved skull is nearly complete and fully disarticulated. Both skulls were assembled for display in the new Late Cretaceous exhibit hall at the Museum of the Rockies. The MOR 008 mount displays the actual fossil material, the MOR 1125 mount is created with resin casts. Missing or incomplete elements were sculpted for each of the two mounts.
During the reconstruction process, further preparation of MOR 008 clearly revealed an alternate arrangement of the palatines, pterygoids, and vomer that is noteably different from previous descriptions. A series of photographs taken during the process enabled comparison of relevant elements from both skulls. Images of MOR 1125 provide additional supporting evidence for the arrangement revealed by MOR 008.
A computed tomography (CT) scan animation sequence of the vomeropterygoid complex of MOR 008 was used to assess the validity of the alternate arrangement without cutting the fossils. The resulting alternate palatal arrangement presented here places the anterior flanges of the pterygoids adjacent to and contacting each other at the midline of the skull. These closely appressed flanges then insert between the paired posterior plates of the vomer, and penetrate well into the middle of the vomer. This revised arrangement may have implications for tyrannosaur phylogeny, ontogeny and functional morphology.