TY - JOUR T1 - Xenoposeidon is the earliest known rebbachisaurid sauropod dinosaur. A1 - Taylor,Michael P, Y1 - 2018/07/06/ PY - 2017/11/15/received PY - 2018/06/20/accepted PY - 2018/7/14/entrez PY - 2018/7/14/pubmed PY - 2018/7/14/medline KW - 3D modelling KW - Dinosauria KW - Laminae KW - Rebbachisauridae KW - Sauropoda KW - Wealden KW - Xenoposeidon SP - e5212 EP - e5212 JF - PeerJ JO - PeerJ VL - 6 N2 - Xenoposeidon proneneukos is a sauropod dinosaur from the Early Cretaceous Hastings Group of England. It is represented by a single partial dorsal vertebra, NHMUK PV R2095, which consists of the centrum and the base of a tall neural arch. Despite its fragmentary nature, it is recognisably distinct from all other sauropods, and is here diagnosed with five unique characters. One character previously considered unique is here recognised as shared with the rebbachisaurid diplodocoid Rebbachisaurus garasbae from the mid-Cretaceous of Morocco: an 'M'-shaped arrangement of laminae on the lateral face of the neural arch. Following the more completely preserved R. garasbae, these laminae are now interpreted as ACPL and lateral CPRL, which intersect anteriorly; and PCDL and CPOL, which intersect posteriorly. Similar arrangements are also seen in some other rebbachisaurid specimens (though not all, possibly due to serial variation), but never in non-rebbachisaurid sauropods. Xenoposeidon is therefore referred to Rebbachisauridae. Due to its inferred elevated parapophysis, the holotype vertebra is considered a mid-posterior dorsal despite its elongate centrum. Since Xenoposeidon is from the Berriasian-Valanginian (earliest Cretaceous) Ashdown Formation of the Wealden Supergroup of southern England, it is the earliest known rebbachisaurid by some 10 million years. Electronic 3D models were invaluable in determining Xenoposeidon's true affinities: descriptions of complex bones such as sauropod vertebrae should always provide them where possible. SN - 2167-8359 UR - https://www.unboundmedicine.com/medline/citation/30002991/Xenoposeidon_is_the_earliest_known_rebbachisaurid_sauropod_dinosaur_ L2 - https://doi.org/10.7717/peerj.5212 DB - PRIME DP - Unbound Medicine ER -