Pterodactyloidea Plieninger, 1901 Pterodactyloidea

O’Sullivan, Michael & Martill, David M., 2018, Pterosauria of the Great Oolite Group (Bathonian, Middle Jurassic) of Oxfordshire and Gloucestershire, England, Acta Palaeontologica Polonica 63 (4), pp. 617-644 : 636-637

Suborder Pterodactyloidea Plieninger, 1901 Pterodactyloidea indet.

Fig. 20 .

Material.—NHMUK PV R 2637 ( Fig. 20 ) from the Taynton Limestone Formation (Bathonian, Middle Jurassic) of Stonesfield, Oxfordshire, is a synsacrum preserved in dorsal view, 21 mm anteroposteriorly and 14 mm laterally. It is poorly preserved, having been crushed flat and heavily worn. There are at least 4 sacral vertebrae with another preserved anterior to these, although it is uncertain if this is a sacral or a dorsal vertebra. The neural spines have broken and while the transverse processes are all present, they are

A significantly damaged anteriorly. The transverse processes are approximately 2–3 mm anteroposteriorly with the posterior pairs horizontally oriented while the anterior transverse processes are angled posteriorly at ~160°. The last vertebra is 3 mm anteroposteriorly and its broken transverse processes appear to connect with the illia. They form the anterior margin of a fenestra twice as broad anteroposteriorly as the previous fenestrae. Synsacra are unique to dinosaurs and pterosaurs among Taynton Limestone vertebrates ( Unwin 2003; Norman 1988). NHMUK PV R 2637 is identified as pterosaurian based on its smooth and ultra-thin bone walls, and its relatively broad transverse processes. In basal pterosaurs, the sacrum comprises 4 vertebrae ( Unwin 2003, 2005). Wukongopterids have at least 5 sacrals ( Lü et al. 2011) and the sacrum tends to be broad medially. In pterodactyloids, there are at least 5 sacral vertebrae ( Wellnhofer 1978) and several have a large fenestra around the first sacral vertebra delineating the anterior and posterior synsacrum. The pterodactyloid synsacrum is elongate, thinning posteriorly throughout its length ( Wellnhofer 1991; Witton 2013). The broad anterior fenestra and the elongate sacrum suggests that NHMUK PV R 2637 may be either a basal monofenestratan with a modified synsacrum ( Lü et al. 2010) or an indeterminate pterodactyloid. If the former it would represent the first evidence of a monofenestratan modifying a module other than the skull and neck. If the latter it represents the earliest occurrence of a pterodactyloid extending the temporal range of pterodactyloids down into the Middle Jurassic, before the Callovian–Oxfordian Kryptodrakon progenitor Andres, Clark, and Xu, 2014 .

Non-pterosaurian material

The fragmentary nature of the Bathonian pterosaur assemblage has led to several specimens being misidentified as pterosaur, although most are small isolated specimens of little note. Buffetaut and Jeffreys (2012) described a supposed pterosaur jaw that Andres et al. (2014) later described as thalattosuchian, an identification with which we concur. The most significant misidentified non-pterosaurian fossil is also the most well-known, the holotype of Rhamphocephalus prestwichi .

Figures

Fig. 20. A synsacrum of?Pterodactyloidea indet. (NHMUK PV R 2637) from Taynton Limestone Formation (Bathonian, Middle Jurassic), Stonesfield, Oxfordshire, UK; in dorsal view. Photograph (A) and accompanying diagram (B), black regions represent the sacral fenestration.