[Palaeontology, Vol. 50, Part 6, 2007, pp. 1547–1564] AN UNUSUAL NEW NEOSAUROPOD DINOSAUR FROM THE LOWER CRETACEOUS HASTINGS BEDS GROUP OF EAST SUSSEX, ENGLAND by MICHAEL P. TAYLOR and DARREN NAISH Palaeobiology Research Group, School of Earth and Environmental Sciences, University of Portsmouth, Burnaby Road, Portsmouth PO1 3QL, UK; e-mails
[email protected];
[email protected] Typescript received 2 June 2006; accepted in revised form 18 December 2006 Abstract: Xenoposeidon proneneukos gen. et sp. nov. is a cannot be referred to any known sauropod genus, and clearly neosauropod represented by BMNH R2095, a well-preserved represents a new genus and possibly a new ‘family’. Other partial mid-to-posterior dorsal vertebra from the Berriasian– sauropod remains from the Hastings Beds Group represent Valanginian Hastings Beds Group of Ecclesbourne Glen, East basal Titanosauriformes, Titanosauria and Diplodocidae; Sussex, England. It was briefly described by Lydekker in X. proneneukos may bring to four the number of sauropod 1893, but it has subsequently been overlooked. This speci- ‘families’ represented in this unit. Sauropods may in general men’s concave cotyle, large lateral pneumatic fossae, complex have been much less morphologically conservative than is system of bony laminae and camerate internal structure show usually assumed. Since neurocentral fusion is complete in that it represents a neosauropod dinosaur. However, it differs R2095, it is probably from a mature or nearly mature ani- from all other sauropods in the form of its neural arch, mal. Nevertheless, size comparisons of R2095 with corre- which is taller than the centrum, covers the entire dorsal sur- sponding vertebrae in the Brachiosaurus brancai holotype face of the centrum, has its posterior margin continuous HMN SII and Diplodocus carnegii holotype CM 84 suggest a with that of the cotyle, and slopes forward at 35 degrees rela- rather small sauropod: perhaps 15 m long and 7600 kg in tive to the vertical.