A study of theropod teeth found in sediments from the Wadhurst Clay Formation suggests tyrannosaurs roamed the Bexhill-on-Sea region of East Sussex around 135 million years ago. The research, published earlier this month in the journal “Papers in Palaeontology” highlights a community of theropods with many different families represented. In addition to the tyrannosaurs, there were large spinosaurids and also dromaeosaurids present.
An Early Cretaceous floodplain around 135 million years ago. A large spinosaurid chases off some tyrannosaurs (left) from the carcass of an ornithopod. Dromaeosaurids (bottom right) dart in to snatch what they can as the larger theropods are preoccupied. Picture credit: Anthony Hutchings
Picture credit: Anthony Hutchings
Wadhurst Clay Formation
The Wadhurst Clay Formation is part of the Hastings Group, which in turn is a component of the Wealden Supergroup. These Lower Cretaceous sediments have a rich diversity of theropod dinosaurs. Fragmentary remains predominate, however, some of the most significant theropod fossils in the whole of Europe have been found in these rocks. Taxa include spinosaurids, neovenatorid allosauroids, tyrannosauroids, and dromaeosaurids. It is noted that most specimens come from the younger Barremian Upper Weald Clay and Wessex formations. The theropod diversity of the older Berriasian–Valanginian Hastings Group remains poorly understood. For example, fragmentary specimens identified so far pose challenges in terms of their phylogenetic relationships and origins.
Berriasian–Valanginian dinosaur fossils are globally scarce. Any insights gleaned from studying the Lower Cretaceous exposures representing Berriasian–Valanginian deposits is welcomed.
The research team examined an assemblage of theropod teeth from the Valanginian Wadhurst Clay Formation. Most of the teeth coming from the Ashdown Brickworks site near Bexhill, East Sussex. Dave Brockhurst, a retired quarryman has spent the last thirty years uncovering fossils from the Ashdown Brickworks. His discoveries have been crucial in helping to better understand the theropod biota of the Wadhurst Clay Formation.
Retired quarryman Dave Brockhurst who has spent the last thirty years uncovering fossils from the Ashdown Brickworks.
Picture credit: University of Southampton
Theropod Dinosaur Fossils are Rare
Dr Chris Barker, visiting researcher at the University of Southampton and lead author of the study explained:
“Meat-eating dinosaurs, properly called theropods are rare in the Cretaceous sediments of southern England. Usually, Isle of Wight dinosaurs attract most of our attention. Much less is known about the older Cretaceous specimens recovered from sites on the mainland.”
For example to read about the discovery to two new spinosaurs from fossils found on the Isle of Wight: Two New Spinosaurids from the Isle of Wight.
It’s the first time tyrannosaurs have been identified in sediments of this age and region. The new Bexhill-on-Sea dinosaurs are represented by teeth, no other body or trace fossils have been found. Fortunately, theropod teeth are complex. They vary in size, morphology and their denticles (serrated edges) can be diagnostic. The researchers used several different techniques to analyse the theropod teeth including phylogenetic analysis along with discriminant and machine learning methods.
Dr Barker added:
“Dinosaur teeth are tough fossils and are usually preserved more frequently than bone. For that reason, they’re often crucial when we want to reconstruct the diversity of an ecosystem. Rigorous methods exist that can help identify teeth with high accuracy. Our results suggest the presence of spinosaurs, mid-sized tyrannosaurs and tiny dromaeosaurs – Velociraptor-like theropods – in these deposits.”
CT scan of the one of the theropod teeth. Picture credit: University of Southampton.
Picture credit: University of Southampton
Tyrannosaurs from the Wadhurst Clay Formation
The discovery of teeth that likely came from tyrannosaurs (tyrannosauroids) is particularly notable. These theropods had not previously been identified in these sediments. They would have been about thirty percent the size of the famous Tyrannosaurus rex of the Late Cretaceous. They probably filled a secondary predator niche in the Wadhurst Clay Formation ecosystem.
Co-author Lucy Handford, a former University of Southampton Master’s student, who is now undertaking a PhD at the University of York, commented:
“Assigning isolated teeth to theropod groups can be challenging, especially as many features evolve independently amongst different lineages. This is why we employed various methods to help refine our findings, leading to more confident classifications. It’s highly likely that reassessment of theropod teeth in museum stores elsewhere will bring up additional discoveries.”
Intriguingly, the study identified representatives of Spinosauridae, Tyrannosauroidea, and Dromaeosauridae, along with some specimens of uncertain classification within Coelurosauria. Notably, these taxa differ from those previously identified in the Wealden Supergroup. For instance, the spinosaurid cannot be linked to Baryonyx, nor can the tyrannosauroid be associated with Eotyrannus. Although the researchers did not designate any new taxa, their findings, in conjunction with other research from the Wadhurst Clay Formation, suggest that theropod diversity during the Valanginian was on a par with that of later Wealden Supergroup formations. This indicates that the distinctive theropod components of Wealden faunas were established early in this well-known geological sequence.
Discovered theropod teeth of (a) spinosaur, (b) tyrannosaur, (c) dromaeosaur, (d) possible tyrannosaur, (e) indeterminate tyrannoraptoran – the group containing tyrannosaurs and dromaeosaurs (Velociraptor and their kin). Note scale bar equals 1 cm. Picture credit Barker et al.
Picture credit: Barker et al
Providing a Unique Perspective on Early Cretaceous European Theropods
Dr Darren Naish (University of Southampton), a co-author of the study added:
“Southern England has an exceptionally good record of Cretaceous dinosaurs, and various sediment layers here are globally unique in terms of geological age and the fossils they contain. These East Sussex dinosaurs are older than those from the better-known Cretaceous sediments of the Isle of Wight, and are mysterious and poorly known by comparison. We’ve hoped for decades to find out which theropod groups lived here, so the conclusions of our new study are really exciting.”
The research project was supervised by Dr Neil Gostling (University of Southampton). He explained that this study highlights the importance of museum collections, curators and local fossil collectors in developing our understanding of the Dinosauria. The scientists acknowledged the assistance of the owners of the Ashdown Brickworks for their co-operation in this project.
Dr Neil Gostling stated:
“Two hundred years after the naming of the first dinosaur, Megalosaurus, there are still really big discoveries to be made. Dinosaur palaeobiology is alive and well.”
The research was funded by the University of Southampton’s Institute for Life Sciences.
Everything Dinosaur acknowledges the assistance of a media release from the University of Southampton in the compilation of this article.
The scientific paper: “Theropod dinosaur diversity of the lower English Wealden: analysis of a tooth-based fauna from the Wadhurst Clay Formation (Lower Cretaceous: Valanginian) via phylogenetic, discriminant and machine learning methods” by Chris T. Barker, Lucy Handford, Darren Naish, Simon Wills, Christophe Hendrickx, Phil Hadland, Dave Brockhurst and Neil J. Gostling published in Papers in Palaeontology.
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