Paper No. 22-5
Presentation Time: 9:30 AM
NEW APPALACHIAN ARMORED DINOSAUR MATERIAL (NODOSAURIDAE, ANKYLOSAURIA) FROM THE MAASTRICHTIAN RIPLEY FORMATION OF ALABAMA
Relative to localities in the west, Late Cretaceous dinosaur remains are extremely rare in the Eastern United States. Even in Laramidia, armored dinosaur specimens, especially those representing juveniles, are relatively rare components of dinosaurian assemblages. We here describe a new specimen of nodosaurid ankylosaur that includes juvenile elements, and is potentially the most complete armored dinosaur specimen from Appalachia. It was most likely recovered from the early–middle Maastrichtian Ripley Formation (based, in part, on nannofossil correlations) near Fort Deposit in south-central Alabama in marine deposits (which is not uncommon for nodosaurs). The specimen includes a basicranium, partial maxilla and right dentary, scapular fragments, partial right ilium, the left half of a cervical neural arch, and numerous vertebral central from the sacral through caudal regions. The basioccipital-basisphenoid suture is open and the basisphenoid is complete. Although the maxillae are ornamented, only incipient osteodermal sculpturing is visible on the mandible. The teeth are distinctly nodosaurid; however, the relatively high crown may be a primitive or juvenile character. Unlike in juvenile ankylosaurids (like Pinacosaurus), there is little dorsoventral flexion to the ilium, a condition more similar to adult nodosaurids. The vertebral centra and their lack of neurocentral fusion are consistent with the morphology and condition of juvenile Pinacosaurus. Other nodosaurid material from Alabama includes largely isolated elements from both adults and juvenile individuals. These elements includes osteoderms, phalanges, vertebrae, , and limb material. Additional field work may recover more nodosaurid material from Alabama, which has considerable ontogenetic and paleogeographic significance.