Abstract
The Jurassic/Cretaceous (J/K) boundary, 145 million years ago, has long been recognised as an extinction event or faunal turnover for sauropod dinosaurs, with many ‘basal’ lineages disappearing. However, recently, a number of ‘extinct’ groups have been recognised in the Early Cretaceous, including diplodocids in Gondwana, and non-titanosauriform macronarians in Laurasia. Turiasauria, a clade of non-neosauropod eusauropods, was originally thought to have been restricted to the Late Jurassic of western Europe. However, its distribution has recently been extended to the Late Jurassic of Tanzania (Tendaguria tanzaniensis), as well as to the Early Cretaceous of the USA (Mierasaurus bobyoungi and Moabosaurus utahensis), demonstrating the survival of another ‘basal’ clade across the J/K boundary. Teeth from the Middle Jurassic–Early Cretaceous of western Europe and North Africa have also tentatively been attributed to turiasaurs, whilst recent phylogenetic analyses recovered Late Jurassic taxa from Argentina and China as further members of Turiasauria. Here, an anterior dorsal centrum and neural arch (both NHMUK 1871) from the Early Cretaceous Wealden Supergroup of the UK are described for the first time. NHMUK 1871 shares several synapomorphies with Turiasauria, especially the turiasaurs Moabosaurus and Tendaguria, including: (1) a strongly dorsoventrally compressed centrum; (2) the retention of prominent epipophyses; and (3) an extremely low, non-bifid neural spine. NHMUK 1871 therefore represents the first postcranial evidence for Turiasauria from European deposits of Early Cretaceous age. Although turiasaurs show clear heterodont dentition, only broad, characteristically ‘heart’-shaped teeth can currently be attributed to Turiasauria with confidence. As such, several putative turiasaur occurrences based on isolated teeth from Europe, as well as the Middle Jurassic and Early Cretaceous of Africa, cannot be confidently referred to Turiasauria. Unequivocal evidence for turiasaurs is therefore restricted to the late Middle Jurassic–Early Cretaceous of western Europe, the Late Jurassic of Tanzania, and the late Early Cretaceous of the USA, although remains from elsewhere might ultimately demonstrate that the group had a near-global distribution.
Highlights
The Late Jurassic is often regarded as a period of heightened sauropod dinosaur diversity, prior to a precipitous decline across the Jurassic/Cretaceous (J/K) boundary (145 million years ago), at which point many ‘basal’ sauropod lineages went extinct (Bakker, 1977; Hunt et al, 1994; Wilson & Sereno, 1998; Upchurch & Barrett, 2005; Barrett, McGowan & Page, 2009; Mannion et al, 2011)
Taxonomic affinities of NHMUK 1871 To determine the taxonomic affinities of NHMUK 1871, it is compared with anteriormost dorsal vertebrae from an array of eusauropods
The presence of camerae in the centrum is consistent with the anteriormost dorsal vertebrae of most eusauropods more derived than Omeisaurus, whereas the absence of clear camellae suggests that NHMUK 1871 lies outside of Titanosauriformes, and that it is not a mamenchisaurid (Wedel, 2003, 2005)
Summary
The Late Jurassic is often regarded as a period of heightened sauropod dinosaur diversity, prior to a precipitous decline across the Jurassic/Cretaceous (J/K) boundary (145 million years ago), at which point many ‘basal’ sauropod lineages went extinct (Bakker, 1977; Hunt et al, 1994; Wilson & Sereno, 1998; Upchurch & Barrett, 2005; Barrett, McGowan & Page, 2009; Mannion et al, 2011). A previously undescribed anterior dorsal centrum and neural arch (NHMUK 1871) of a turiasaur from the Early Cretaceous Wealden Supergroup of the UK is presented. NHMUK 1871 is a relatively complete, but poorly preserved, anterior dorsal centrum and neural arch from an unknown Early Cretaceous ‘Wealden’ locality of the UK. Material: NHMUK 1871, a relatively complete, but poorly preserved, anterior dorsal centrum (Fig. 1) and separate neural arch (Fig. 2). The centrum is poorly preserved and incomplete, especially around the ventrolateral margins of its posterior cotyle (Fig. 1; see Table 1 for measurements). The dorsoventrally low, unbifurcated neural spine projects only very slightly above the level of the postzygapophyses, and is anteroposteriorly narrow, especially towards the midline (Fig. 2)
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