The Ankylosaurs are Ornithischian Dinosaurs noted for their broad body, short limbs and extensive covering of dermal armour on the head, body and tail. They are a diverse group, found on all continents, but reaching their greatest diversity on the continents of the former Laurasian landmass, i.e. North America, Europe, and Asia. They split from their sister group, the Stegosaurs, in the Early or early Middle Jurassic, but appear to have remained a minor component of most ecosystems until the Early Cretaceous, when they underwent a significant radiation, remaining a significant member of the herbevore community until their demise in the End Cretaceous extinction.
A number of Ankylosaurs have been described from the UK, from the Middle Jurassic onwards, although the group reach their maximum abundance in the UK in the Early Cretaceous Wealden Group of southern England. For a long time, all Ankylosaurs from the Wealden Group were referred to two species, Polacanthus foxii and Hylaeosaurus armatus, but this is now thought likely to hide considerable diversity, as the Wealden Group is thought to cover at least 8 million years of time, including all of the Barremian Stage and part of the Aptian.
Traditionally, all Ankylosaur material from the Isle of Wight was referred to Polacanthus foxii, but a recent study of Ankylosaur diversity within the Wealden Group, led by Thomas Raven of the Fossil Reptiles, Amphibians and Birds Section at the Natural History Museum, has suggested that this name should be restricted to the holotype specimen, NHMUKPV R175, and other specimens should be considered taxonomically uncertain until re-examined. One notable specimen examined in Raven et al.'s study was IWCMS 1996.153, known as the Spearpoint Ankylosaur, which was shown to be particularly different to the Polacanthus foxii holotype, and not likely to be closely related.
In a paper published in the Journal of Systematic Palaeontology on 15 June 2023, Stuart Pond, also of the Fossil Reptiles, Amphibians and Birds Section at the Natural History Museum, Sarah-Jane Strachan of the Department of Earth Sciences at University College London, Thomas Raven (again), Martin Simpson of Lansdowne on the Isle of Wight, Kirsty Morgan of Fayetteville in Arkansas, and Susannah Maidment, again of the Fossil Reptiles, Amphibians and Birds Section at the Natural History Museum, formally describe the Spearpoint Ankylosaur as the holotype of a new species.
The Wessex Group consists of a series of terrestrial, lacustrine, flu-vial and lagoonal deposits which outcrop in the Wessex Sub-basin of the Isle of Wight and the Weald Sub-basin of south-east England. On the Isle of Wight the group comprises two formations, the Wessex Formation, considered Barremian in age, and the Vectis Formation, thought to be late Barremian to early Aptian. The Wessex Formation is a sequence about 180 m thick, consisting of variegated mudstones and interbedded sandstones deposited as river channel, floodplain and point bar deposits by a high-sinuosity river system flowing west to east. The overlying Vectis Formation is thought to have been laid down in a shallow lagoon. The largest exposures of both formations are on the southwestern coast of the Isle of Wight, with smaller exposures at Yaverland on the south-east coast.
The Wessex Formation is thought to have been laid down in a Mediterranean climate, with distinctive dry and wet seasons, the latter associated with periodic flood events in which debris flows including large trees and Dinosaur remains were swept down from the (now lost) highlands from which the river descended, and were deposited on the flood plain. This formation is rich in fossils, producing numerous Plant (particularly Gymnosperms), Invertebrates, trace fossils, and a diverse Vertebrate assemblage, including Bony Fish, Turtles, Crocodilians, Pterosaurs and Dinosaurs.
The Spearpoint Ankylosaur was discovered within the Compton Chine to Steephill Cove Site of Special Scientific Interest, about 50 m to the west of Chilton Chine. Chines on the Isle of Wight, are gullies which cut into the overlying chalk grassland by seasonal streams, and emerging from the cliffs as waterfalls. These features never erode down to beach level, as the cliffs are eroded backwards by the action of the sea faster than the chines are eroded downwards by the streams, and form a unique environment with their own distinctive flora and fauna, including many rare Plants and Insects.
In November 1993 fossil hunter Gavin Leng found several Ankylosaur vertebrae on beach, which he later donated to the Dinosaur Isle Museum. The following spring another fossil hunter Lin Spearpoint, discovered the remainder of the skeleton in the cliffs above, on land belonging to dairy farmer Richard Fisk. Fisk gave permission for Lin Spearpoint, Dick Spearpoint, and Martin Simpson, to excavate the skeleton, which was then prepared by Lin Spearpoint, housed at the University of Southampton, where it was the subject of several MSci, MRes and PhD projects, some of which were carried out by Stuart Pond, Sarah-Jane Strachan, and Kirsty Morgan, temporarily displayed at the SeaCity Museum, Southampton, and eventually acquired by the Dinosaur Isle Museum.
Pond et al. formally describe the Spearpoint Ankylosaur as the holotype of a new species, Vectipelta barretti, where 'Vectipelta' means 'Vectis-shield' (Vectis was the name used by the Romans for the Isle of Wight), and 'barretti' honours Paul Barrett of the Natural History Museum, in recognition of his major and ongoing contributions to Dinosaurian Vertebrate palaeontology, and his importance to Stuart Pond, Thomas Raven and Susannah Maidment as a mentor, supervisor, colleague and friend.
Geological setting and stratigraphy. (A) Map of Isle of Wight with the extent of Wessex Sub-basin marked in orange, and the site of the Vectipelta barretti (IWCMS 1996.153 and IWCMS 2021.75) excavation indicated by the black arrow. (B) Schematic stratigraphical log of the outcrop between Sudmore Point and Ship Ledge showing the approximate stratigraphical location of Vectipelta barretti (IWCMS 1996.153 and IWCMS 2021.75). Pond et al. (2023).The new species is described from two specimens, both believed to have come from the same individual and therefore treated as one. WCMS1996.153 comprises portions of four cervical vertebrae and six free dorsal vertebrae discovered on the foreshore by Gavin Leng in 1993, while IWCMS 2021.75 comprises five fused dorsal vertebrae, forming the sacral rod, fragments of several dorsal ribs, a fused sacrum made up of four and a half fused vertebrae, thirteen caudal vertebrae, and fragments of four more, the proximal part of the left scapula, the proximal and distal ends of the left humerus, a possible ulna fragment, multiple pieces of the iliosacral block, including parts both the left and right ilia, both pubes, fused to the anteromedial margins of the acetabula, a more-or-less complete left ischium, some possible fibula fragments, and second metatarsal, the sacral shield, a large number of osteoderms, and three recurved spines. Specimen IWCMS 2021.75 was found lying on its back, with its (missing) head pointing towards the cliff face, leading to the assumption that the cervical and upper dorsal vertebrae of WCMS1996.153 came from the same individual. Pond et al, note that several years prior to the discovery of WCMS1996.153, a beach-rolled Ankylosaur braincase was found at the same location by fossil hunter David Cooper, and acquired by the University of Cambridge's Sedgwick Museum, and a partial femur and posterior part of an ilium were found nearby by David Richards in the 1990s and donated to the Natural History Museum. These specimens may also relate to the Spearpoint Ankylosaur, but all are heavily eroded, making it impossible to assess them with any confidence, so they were excluded from the study.
The recurved spines of the Spearpoint Ankylosaur are notable, as NHMUKPV R175, the holotype of Polacanthus foxii, lacks any such structure, supporting the idea that the two are quite different Animals. Some spines assigned to Polacanthus sp. have been described from Early Cretaceous of Soria, Spain, but these are also unlikely to derive from that genus. Recurved spines are known in a wide range of Ankylosaurs, including the other Wealden Group species, Hylaeosaurus armatus, but the form of the Spearpoint Ankylosaur's spines is different to any of these, supporting the idea that it should be described as a new species.
Understanding the diversity of Early Cretaceous Ankylosaurs is not just important because we are interested in Dinosaurs; it has implications for our understanding of Mesozoic ecosystems and geology as a whole. The Jurassic is believed to have ended with a mass extinction event, although the nature of this is poorly understood. Terrestrial deposits with good fossil preservation are rare from the Early Cretaceous, leading to the apparent emergence of a quite new ecosystem in the Middle Cretaceous. However, the clustering of multiple specimens from diverse groups under a few poorly constrained species names in Early Cretaceous deposits, as has happened with Wealden Ankylosaurs (and, it has also been suggested, Iguanodontids), could be hiding a more gradual faunal turnover during this interval.
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