A NEW PARTIAL SKELETON OF XIPHACTINUS AUDAX WITH A WELL-PRESERVED NEUROCRANIUM FROM THE LATE CRETACEOUS TROPIC SHALE OF SOUTHERN UTAH
MNA V10796 (Museum of Northern Arizona, Flagstaff) is a partial skeleton of Xiphactinus audax discovered in 2012 and excavated in 2014-15 from the Tropic Shale in Glen Canyon National Recreation Area. The specimen was approximately 0.3 meters below the lower couplet of Bentonite D. MNA V10796 was partially articulated, is moderately compressed and heavily fractured. The specimen includes a well-preserved neurocranium, two fragmentary teeth, five abdominal vertebrae, a couple of ribs, and a partial pectoral fin. The skeletal material from MNA V10796 is morphologically similar to previously described specimens of X. audax. The neurocranium, which is the first to be described from a specimen of X. audax from the Tropic Shale, is from the right side of the skull and includes the supraoccipital, epiotic, parietal, pterotic, sphenotic, dermosphenotic, frontal, postfrontal, prefrontal, ethmoid, and the premaxilla. The teeth have glassy, smooth, enamel surfaces, are straight with no carinae, and are oval in cross-section. The vertebrae are strongly amphicoelous, perforated with a small notochordal canal, and are circular in anteroposterior view. This specimen adds to the more limited information known about X. audax along the western side of the Western Interior Seaway.