DOI: 10.5061/dryad.25
title: Data from: An unusual new neosauropod dinosaur from the lower Cretaceous Hastings Beds Group of East Sussex, England

description: Xenoposeidon proneneukos gen. et sp. nov. is a neosauropod represented by
 BMNH R2095, a well-preserved partial mid-to-posterior dorsal vertebra from
 the Berriasian–Valanginian Hastings Beds Group of Ecclesbourne Glen, East
 Sussex, England. It was briefly described by Lydekker in 1893, but it has
 subsequently been overlooked. This specimen's concave cotyle, large
 lateral pneumatic fossae, complex system of bony laminae and camerate
 internal structure show that it represents a neosauropod dinosaur.
 However, it differs from all other sauropods in the form of its neural
 arch, which is taller than the centrum, covers the entire dorsal surface
 of the centrum, has its posterior margin continuous with that of the
 cotyle, and slopes forward at 35 degrees relative to the vertical. Also
 unique is a broad, flat area of featureless bone on the lateral face of
 the arch; the accessory infraparapophyseal and postzygapophyseal laminae
 which meet in a V; and the asymmetric neural canal, small and round
 posteriorly but large and teardrop-shaped anteriorly, bounded by arched
 supporting laminae. The specimen cannot be referred to any known sauropod
 genus, and clearly represents a new genus and possibly a new ‘family’.
 Other sauropod remains from the Hastings Beds Group represent basal
 Titanosauriformes, Titanosauria and Diplodocidae; X. proneneukos may bring
 to four the number of sauropod ‘families’ represented in this unit.
 Sauropods may in general have been much less morphologically conservative
 than is usually assumed. Since neurocentral fusion is complete in R2095,
 it is probably from a mature or nearly mature animal. Nevertheless, size
 comparisons of R2095 with corresponding vertebrae in the Brachiosaurus
 brancai holotype HMN SII and Diplodocus carnegii holotype CM 84 suggest a
 rather small sauropod: perhaps 15 m long and 7600 kg in mass if built like
 a brachiosaurid, or 20 m and 2800 kg if built like a diplodocid.
description: Xenoposeidon Proneneukos
 Specimen Photo Anterioranterior3.jpgXenoposeidon Proneneukos Specimen Photo Posteriorposterior1.jpgInterpretive Drawing of Xenoposeidon Proneneukos gen. et sp. nov. HolotypeInterpretive drawing of Xenoposeidon proneneukos gen. et sp. nov. holotype in A, left lateral, B, right lateral, C, anterior, and D, posterior views. Scale bar represents 200 mm. Breakage is indicated by diagonal hatching. The PPDL (preserved only on the left side) is a sheet of bone projecting anterolaterally from the neural arch with its anterolateral margin running dorsoventrally, but which is broken off just dorsal to the parapophysis.figure4-interpretation.jpegMaps Indicating Location of Ecclesbourne GlenMaps indicating location of Ecclesbourne Glen, near Hastings, East Sussex, England, the probable discovery site of the holotype of Xenoposeidon proneneukos gen. et sp. nov.figure1-map.jpegXenoposeidon Proneneukos Specimen Photo Oblique Left Anterolateraloblique-left-anterolateral.jpgXenoposeidon Proneneukos Specimen Photo Dorsaldorsal.jpgXenoposeidon proneneukos specimen photo right lateralright-lateral1.jpgXenoposeidon Proneneukos Specimen Photo Oblique Right Posterolateraloblique-right-posterolateral.jpgXenoposeidon Proneneukos Specimen Photo Oblique Left Posterolateraloblique-left-posterolateral.jpgXenoposeidon Proneneukos gen. et sp. nov. Holotype, Speculative ReconstructionXenoposeidon proneneukos gen. et sp. nov. holotype, mid to posterior dorsal vertebra BMNH R2095, speculative reconstruction, in left lateral view. The location of the prezygapophyses, postzygapophyses and diapophyses are inferred with some confidence from the preserved laminae; the neural spine is based on an idealized slender neosauropod neural spine. Scale bar represents 200 mm.figure5-reconstruction.jpegXenoposeidon Proneneukos Specimen Photo Left Lateralleft-lateral1.jpgNexus Filer2095.nexXenoposeidon Proneneukos Specimen Photo Oblique Anterioroblique-anterior-with-a-hint-of-right-lateral.jpgPhylogenetic Relationships of Xenoposeidon ProneneukosPhylogenetic relationships of Xenoposeidon proneneukos, produced using PAUP* 4.0b10 on the matrix of Harris (2006) augmented by Xenoposeidon, having 31 taxa and 331 characters. A, strict consensus of 1089 most parsimonious trees (length, 785; CI, 0.5248; RU, 0.6871, RC = 0.3606). B, 50 per cent majority rule consensus. Clade names are positioned to the right of the branches that they label; occurrence percentages are positioned to the left of these branches.figure6-phylogeny.jpegXenoposeidon Proneneukos gen. et sp. nov. HolotypeXenoposeidon proneneukos gen. et sp. nov. holotype in A, left lateral, B, right lateral, C, anterior, and D, posterior TEXT-FIG. 4. views. Scale bar represents 200 mm.figure3-photos.jpegXenoposeidon Proneneukos Specimen Photo Posteriorposterior4.jpgXenoposeidon Proneneukos Specimen Photo Oblique Left Posterodorsolateraloblique-left-posterodorsolateral.jpgXenoposeidon Proneneukos Specimen Photo Oblique Right Posterodorsolateraloblique-right-posterodorsolateral.jpgXenoposeidon Proneneukos Specimen Photo Detaildetail2.jpgXenoposeidon Proneneukos Specimen Photo Anterior Centrumanterior-centrum-no-label.jpgXenoposeidon Proneneukos Specimen Photo Oblique Anteroventraloblique-anteroventral.jpgXenoposeidon Proneneukos Specimen Photo Detaildetail1.jpgXenoposeidon Proneneukos Specimen Photo Anterioranterior1.jpgXenoposeidon Proneneukos Specimen Photo Posteriorposterior2.jpgXenoposeidon Proneneukos Specimen Photo Oblique Right Anterolateraloblique-right-anterolateral1.jpgXenoposeidon Proneneukos Specimen Photo Right Lateralright-lateral2.jpgXenoposeidon Proneneukos Specimen Photo Anterioranterior2.jpgXenoposeidon Proneneukos Specimen Photo Left Lateralleft-lateral2.jpgXenoposeidon Proneneukos Specimen Photo Posteriorposterior3.jpgSchematic Lithostratigraphy of the WealdenSchematic lithostratigraphy of the Wealden indicating the origin of the holotype of Xenoposeidon proneneukos gen. et sp. nov. within the Ashdown Beds Formation of the Hastings Beds Group.figure2-stratigraphy.jpegXenoposeidon Proneneukos Specimen Photo Anterioranterior4.jpg