Over recent years, myself and colleagues at the University of Southampton have published a series of studies on the spinosaurid theropods of the English Wealden Supergroup (Barker et al. 2021, 2022, 2023a). And we’ve succeeded in improving our knowledge of Wealden spinosaurid diversity. But wait — there’s more!
Caption: a Hastings spinosaurid montage, featuring images of the specimen discussed further below and some of the analyses we did on it.
Firstly, what’s the Wealden? It’s a Lower Cretaceous sedimentary unit famous for the great number of dinosaurs and other fossils it reveals. Today sees the latest of our publications on Wealden spinosaurids; it’s by Chris Barker, Neil Gostling and myself, and appears in the open access journal PeerJ (Barker et al. 2023b).
And while the results are interesting, arguably newsworthy… don’t get your hopes up. We aren’t (this time) talking about fossils that can be considered spectacular or impressive.
A Hastings spinosaurid specimen. This latest study concerns the spinosaurid tooth HASMG G369a, accessioned at Hastings Museum and Art Gallery in East Sussex, England and part of a collection gifted by Reverend Pierre Teilhard de Chardin during the first half of the 20th century. Teilhard is best known for his metaphysical writings on humanity’s place in the cosmos (incidentally, an area relevant to my research on Dale Russell and the dinosauroid), but his interest in, and discovery of, Wealden fossils is well known among specialists.
Caption: the Hastings spinosaurid tooth HASMG G369a, in (A) lingual, (B) basal, (C) mesial, (D) distal and (E) labial views, with close-ups of its surface texture on the labial side (F-H). Scale bar = 10 mm, 1 mm in F-H. Image: Barker et al. (2023b).
The precise provenance of the Hastings tooth is a little murky but it almost certainly came from the Wadhurst Clay or Tunbridge Wells Sands formations close to Hastings (Barker et al. 2023b), which in turns means it comes from the Valanginian stage of the Lower Cretaceous*. Theropods from this part of the Wealden (and, indeed, this part of the Cretaceous) are rare, so any additional information on their diversity is welcome.
* I should add as an aside that we were initially working on the assumption that the specimen was from the Purbeck (way down at the base of the Cretaceous) – an idea arrived at thanks to an associated hand-written note – but ultimately decided that a Purbeck origin was based on a misunderstanding.
Caption: geographical distribution of the Wealden spinosaurid discussed here, from Barker et al. (2023b). 1, 2 = Upper Weald Clay specimens (the Baryonyx walkeri holotype and indeterminate Ewhurst Brickworks specimen); 3 = Suchosaurus cultridens from the Grinstead Clay Formation; 4 = indeterminate spinosaurid specimens from the Wadhurst Clay Formation of Bexhill.
We’re confident that the Hastings tooth is from a spinosaurid, since it possesses the cone-like form and proportionally tiny denticles unique to this group (Barker et al. 2023b). We can eliminate the only other group of animals worthy of consideration – crocodyliforms – since they differ from spinosaurids (and the Hastings tooth specifically) in denticle form, crown ornamentation, size and other features too (Barker et al. 2023b). The tooth’s crown is only 1.3 cm long, which means that it most likely originated from the rear parts of the jaws.
For decades now, people have thought it likely that isolated Wealden spinosaurid teeth should be regarded as belonging to Baryonyx, the iconic English spinosaurid found in Surrey in 1983 and named in 1986 (Charig & Milner 1986, 1997). But many of the teeth in question are (in geological terms) quite a bit older than the remains of Baryonyx, and also different from its teeth in detailed anatomy. For these reasons, it’s been suggested that at least some Wealden spinosaurid teeth might not be from Baryonyx at all (Naish & Martill 2007, Buffetaut 2010, Naish 2011), and in fact they might show that Wealden spinosaurid diversity is higher than otherwise thought. How do we go further with this hypothesis? How do we test it?
Caption: the approximate stratigraphic distribution of spinosaurids in the Wealden Supergroup as understood right now. The Hastings specimen discussed here is from the Hastings Group, and thus from the Valanginian. Establishing the presence of spinosaurids here is not novel at all, but working out what kind of spinosaurid we’re dealing with is a worthy endeavour. Image: Darren Naish.
Theropod teeth are complex objects, differing in their ratios of base length to crown height, in their degree of curvature, their surface texture, in the distribution, shape, proportional size and spacing of their serrations, and much else. There are, in short, numerous details that can be codified, and (in cases) quantified and analysed statistically. Today, it’s easier than ever before (though still – by no means – actually ‘easy’) to use statistical tests of different sorts in the analysis of a given fossil specimen or specimens. It’s also generally agreed that the combined use of different tests increases the robustness of a conclusion. Inspired by recent studies that have also been devoted to the identification of theropod teeth (Hendrickx & Mateus 2014, Hendrickx et al. 2015, 2019, 2020), we did exactly this, subjecting the Hastings tooth to separate phylogenetic, discriminant and cluster analyses (Barker et al. 2023b).
Baryonyx in the Valanginian? Probably not. What did we find? When included in phylogenetic tests, the Hastings tooth is nothing to do with Baryonyx, and in fact occupies a position outside both Spinosaurinae and Baryonychinae, the two constituent clades within the group (Barker et al. 2023b). When included in statistical tests that compare tooth proportions and other features, it again never grouped with Baryonyx, but was closer to baryonychines than to spinosaurines (Barker et al. 2023b).
Caption: position for the Hastings spinosaurid tooth recovered in our phylogenetic analysis (strict consensus at left, reduced consensus at right). It never grouped with Baryonyx, and indeed was not recovered as a baryonychine. Image: Barker et al. (2023b).
While we really shouldn’t go any further at this point – we’re talking of a single tooth, after all – the takehome is that the Hastings tooth is not from Baryonyx, and whether it is or isn’t referable to that genus is the primary hypothesis we were aiming to test. Here is another indication, then, that isolated Wealden spinosaurid teeth shouldn’t be referred to Baryonyx by default. And the specimen at least hints at the presence of additional diversity within Wealden spinosaurid that’s yet to be properly documented: in other words, that isolated teeth demonstrate a sort of previously ‘hidden’ diversity within this group (Barker et al. 2023b).
Caption: results of one of the several discriminant analyses we applied to the Hastings specimen (visible at far right) and other spinosaurid specimens. HASMG G369a didn’t group with Baryonyx, though is closer to baryonychine clusters than to spinosaurine ones. Of incidental interest is that the ‘cf. Baryonychinae’ specimen at upper right (a Santonian tooth from the Majiacun Formation of China, suggested to be an especially late-occurring spinosaurid) never grouped with spinosaurids in our study, meaning that it’s likely not part of this group. Image: Barker et al. (2023b).
Pending the discovery of additional Wealden spinosaurid remains that include teeth of the same sort, here’s where things end on this particular specimen. However, this study was sort of a test-run. Numerous other isolated spinosaurid teeth are known from the Wealden, and ‘all’ we have to do now is run similar tests on them too…
As ever, thanks to my co-authors Chris and Neil for collaboration on this study, and to staff at the Hastings Museum and Art Gallery for assistance, access, and continued curation of the specimen.
For previous TetZoo articles on spinosaurids, British theropods and associated issues (some links here are to wayback machine versions due to destruction or paywalling of everything at versions 2 and 3), see…
Of Becklespinax and Valdoraptor, October 2007
The world’s most amazing sauropod, November 2007
Oh no, not another new Wealden theropod!, June 2009
Concavenator: an incredible allosauroid with a weird sail (or hump)... and proto-feathers?, September 2010
The Wealden Bible: English Wealden Fossils, 2011, November 2011
Ostrich dinosaurs invade Europe! Or do they?, June 2014 (every archived version of this article lacks the original illustrations, sorry)
Theropod Dinosaurs of the English Wealden, Some Questions (Part 1), March 2020
Introducing ‘Unexpected Isle of Wight Air-Filled Hunter’, a New English Theropod Dinosaur, September 2020
Dr Angela Milner and the Discovery of Baryonyx, August 2021
Two New Spinosaurid Dinosaurs from the English Cretaceous, September 2021
A Giant Spinosaurid Dinosaur from the Cretaceous of the Isle of Wight, June 2022
A brain for Baryonyx: using CT-scanning to examine British spinosaurid brains, February 2023
Refs - -
Buffetaut, E. 2010. Spinosaurs before Stromer: early finds of spinosaurid dinosaurs and their interpretation. In Moody, R. T. J., Buffetaut, E., Naish, D. & Martill, D. M. (eds) Dinosaurs and Other Extinct Saurians: A Historical Perspective. Geological Society, London, Special Publications 343, pp. 175-188.
Charig, A. J. & Milner, A. C. 1986. Baryonyx, a remarkable new theropod dinosaur. Nature 324, 359-361.
Charig, A. J. & Milner, A. C. 1997. Baryonyx walkeri, a fish-eating dinosaur from the Wealden of Surrey. Bulletin of the Natural History Museum 53, 11-70.
Hendrickx, C. & Mateus, O. 2014. Abelisauridae (Dinosauria: Theropoda) from the Late Jurassic of Portugal and dentition-based phylogeny as a contribution for the identification of isolated theropod teeth. Zootaxa 3759, 1-74.
Hendrickx, C., Mateus, O. & Araújo, R. 2015. The dentition of megalosaurid theropods. Acta Palaeontologica Polonica 60, 627-642.
Hendrickx, C., Mateus, O., Araújo, R. & Choiniere, J. 2019. The distribution of dental features in non-avian theropod dinosaurs: Taxonomic potential, degree of homoplasy, and major evolutionary trends. Palaeontologia Electronica 22, 1-110.
Hendrickx, C., Tschopp, E. & Ezcurra, M. d. 2020. Taxonomic identification of isolated theropod teeth: the case of the shed tooth crown associated with Aerosteon (Theropoda: Megaraptora) and the dentition of Abelisauridae. Cretaceous Research 108, 104312.
Naish, D. 2011. Theropod dinosaurs. In Batten, D. J. (ed.) English Wealden Fossils. The Palaeontological Association (London), pp. 526-559.
Naish, D. & Martill, D. M. 2007. Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia. Journal of the Geological Society, London 164, 493-510.
