New Insights into the Cranial Anatomy of Panoplosaurus mirus (Dinosauria: Nodosauridae) using Computed Tomography

The holotype skull (CMN 2759) of the Late Cretaceous nodosaurid Panoplosaurus mirus Lambe 1919 is re-examined using computed tomography (CT) imaging, revealing important new information about the internal anatomy. Previously unknown regions of the skull are described, including the basicranium and palate, and the endocranial anatomy in Panoplosaurus is examined from CT-rendered models of the brain and nasal cavities. The occurrence of grooved vomers and convoluted nasal passages are confirmed in Panoplosaurus, while decreased brain flexure relative to other nodosaurids suggests there is greater variability in the paleoneurology of Nodosauridae than previously appreciated. The unique pattern of cranial ornamentation in Panoplosaurus is also determined to be taxonomically significant, and the generic separation of Panoplosaurus and the closely related Edmontonia is supported. Further, intraspecific variation in the cranial ornamentation of Panoplosaurus is revealed, based on the presence or absence of the internasal caputegulum.