[N] 2006 A new Titanosauriform from the Cedar Mountain formation
Chure, D.J., Britt, B. & Greenhalgh, B. (2006) A new Titanosauriform sauropod with abundant skullmaterial from the Cedar Mountain formation, Dinosaur National Monument. JVP 26(3) Abstracts pp.50
The study of sauropods is hampered by a dearth of skulls. Most skulls pertain to Middle and Late Jurassic taxa and the Cretaceous skull record is extremely limited. Here, we here report a new titanosauriform represent by multiple skulls. The specimens were recovered from a fluvial sandstone posited in the middle of the Cedar Mountain Fm., 32 m above the contact with the underlying Morrison Formation. Cranial materials include 1) a spectacularly complete 3-D skull, 2) a nearly complete disarticulated skull, 3) the front one-third of an articulated skull, and 4) a braincase. The skulls were found with associated postcranial elements.
This taxon is the best known Cretaceous sauropod for cranial material & has one of the best skull records for the group. Salient skull characters include an incomplete internarial bar, retracted and confluent external nares, narial fossa absent, quadrate vertical, basipterygoid processes short, dentary with external mandibular fenestra and retroarticular process, unexpanded tooth crowns, tooth to tooth wear, and low tooth count (4 pmx, 10 max, 13 dent). The cervical centra are long, camellate, and bear elongate ribs spanning three centra. Dorsal rib heads have large pneumatic foramina. The humerus is long and gracile. Preliminary phylogenetic analysis places this sauropod as a basal titanosauriform.
The skull, however, differs markedly from those of basal macronarians (Camarasaurus, Brachiosaurus, and Euhhelopus) in 1) lacking a large arching internarial bar, 2) having
small, confluent external nares, and 3) lacking a narial fossa. In these features it more closely resembles the skull in diplodcoids and the titanosaurs Rapetosaurus, Nemegtosaurus, and Quaesitosaurus. This suggests that the skull morphology of the basal macronarians is derived and the similarity between diplodocoids and Titanosauriforms did not evolve in parallel but instead represents the general skull architecture for the Neosauropoda.