Researchers have named a new species of iguanodontian dinosaur from fossils found on the Isle of Wight.  The dinosaur has been named Comptonatus chasei.  The fossil material represents the most complete iguanodontian skeleton discovered in the Wealden Group for over a hundred years.  This new taxon has been erected based on numerous unique characteristics (autapomorphies) related to the skull, the straight dentary bone and a markedly expanded pubic hip bone described as being “the size of a dinner plate”.

A view of the head of the newly described iguanodontian Comptonatus chasei. Picture credit: John Sibbick.

Comptonatus chasei

The fossil material is around 125 million years old (Barremian faunal stage). The dinosaur fossils was found in the cliffs of Compton Bay on the Isle of Wight in 2013 by fossil collector Nick Chase, before he tragically died of cancer.  Dr Jeremy Lockwood, helped with the excavation of the bones and teeth. He then spent years carefully comparing these fossils to other Wealden Group iguanodontians before he was confident that these fossils represented a new species.

Dr Jeremy Lockwood walking on the beach in front of the cliffs that mark the excavation site. Picture credit: University of Portsmouth.

Dr Lockwood has become synonymous with Isle of Wight ornithopods along with Professor David Martill (University of Portsmouth) and Professor Susannah Maidment (London Natural History Museum).  These three scientists described Brighstoneus simmondsi, another Isle of Wight ornithopod in 2021.  The discovery of Comptonatus chasei demonstrates that these dinosaurs were particularly diverse during the Barremian to early Aptian faunal stages.

Lateral views of the skulls of three taxa of Isle of Wight iguanodontian dinosaurs. Comptonatus chasei (A), Brighstoneus simmondsi (B) and Mantellisaurus atherfieldensis (C). Picture credit: University of Portsmouth.

Honouring the Late Nick Chase

A total of 149 fossil bones were collected.  The genus name translates as “Compton thunderer”.  This dinosaur was named after Compton Bay where the fossils were found and the “thunderer” element of the genus name relates to the large size of this dinosaur.   Bone histology indicates that the animal was around five or six years old when it died. It is estimated to have weighed around nine hundred kilograms.

The species name honours Nick Chase, winner of the Palaeontological Association’s Mary Anning Award in 2018, who made the initial discovery and through his lifetime contributed enormously to the collections at the Dinosaur Isle Museum on the Isle of Wight, and the Natural History Museum, London.

The late Nick Chase who found the fossil remains in 2013. The species name honours him, a winner of the Palaeontological Association’s Mary Anning Award in 2018, Nick Chase made the initial discovery. During his lifetime he contributed enormously to the study of the dinosaur biota of the Wessex Formation. Picture credit: University of Portsmouth.

Dr Lockwood commented:

“Nick had a phenomenal nose for finding dinosaur bones – he really was a modern-day Mary Anning. He collected fossils daily in all weathers and donated them to museums. I was hoping we’d spend our dotage collecting together as we were of similar ages, but sadly that wasn’t to be the case. Despite his many wonderful discoveries over the years, including the most complete Iguanodon skull ever found in Britain, this is the first dinosaur to be named after him.”

The Comptonatus chasei excavation in 2013. Nick Chase (in the foreground sketching), Steve Hutt (blue jumper), Jeremy Lockwood (wearing gloves), and Penny Newberry examining the exposed fossil material. Picture credit: University of Portsmouth.

Unique Autapomorphies

During the collection and initial preparation it was thought that these fossils represented a Mantellisaurus atherfieldensis. However, a detailed study identified several autapomorphies (unique characteristics) that led to the erection of a new taxon.

Dr Lockwood explained:

“I’ve been able to show this dinosaur is different because of certain unique features in its skull, teeth and other parts of its body. For example its lower jaw has a straight bottom edge, whereas most iguanodontians have a jaw that curves downwards. It also has a very large pubic hip bone, which is much bigger than other similar dinosaurs. It’s like a dinner plate!”

The large pubis bone of Comptonatus pubis. The enlarged blade-like feature of the pubis is a unique characteristic that helped to define this new taxon. Picture credit: University of Portsmouth.

The scientists are uncertain as to why the pubic hip bone is so large. It could have been for muscle attachments indicating that this ornithopod had a different mode of locomotion. Perhaps it could have helped support the large stomach, or played a role in respiration.

The Geological Setting of Comptonatus chasei

Comptonatus chasei and Brighstoneus simmondsi fossils are associated with the Wessex Formation of the Wealden Group.  However, the deposits where Brighstoneous fossils have been found might be two million years older than the strata associated with C. chasei.  Conversely, Mantellisaurus atherfieldensis is geologically younger than Comptonatus.  Mantellisaurus fossils seem confined to the overlying Vectis Formation (Wealden Group).  This means that Comptonatus and Brighstoneus lived during the early Barremian faunal stage of the Cretaceous.  Mantellisaurus lived several million years later (late Barremian).

The scientists state that the Wessex Formation may have supported a greater diversity than previously realised, or that evolutionary and or migratory pressures resulted in faunal turnover. Comptonatus provides further evidence for a greater iguanodontian diversity and it is now unclear as to which iguanodontian taxon or taxa dominated the Wessex sub-basin during the Barremian.  In addition, the researchers postulate that a reassessment of ornithopod fossil material may be required, as with our improved understanding of the differences between these taxa, more new species might be identified.

Isle of Wight Dinosaur Taxa

Despite only four new dinosaur species being described on the Isle of Wight in the whole of the 20th century, there have been eight new species named in the last five years.  A remarkable number of new dinosaur taxa have been described from fossils found on the Isle of Wight. Ornithischians such as Vectidromeus insularis, Brighstoneus simmondsi and Vectipelta barretti have been named.

To read more about Vectidromeus insularis: Vectidromeus – A New Hypsilophodontid.

An article on Brighstoneus simmondsi: A New Iguanodontid from the Isle of Wight.

A scale drawing of the recently described Isle of Wight iguanodontian Brighstoneus.  CollectA added a model of Brighstoneus simmondsi to their CollectA Age of Dinosaur Popular range of figures.  Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

A new, armoured dinosaur from the Isle of Wight described in 2023 (Vectipelta barretti): New Armoured Dinosaur Honours Natural History Museum Professor.

In addition, several theropod dinosaurs have been described including Vectiraptor greeni, Ceratosuchops inferodios and Riparovenator milnerae. Furthermore, there is evidence of a gigantic spinosaurid (the “white rock spinosaurid”). These discoveries suggest that the Wessex Formation supported a greater diversity of dinosaurs than previously realised. It could also indicate a substantial faunal turnover during the deposition of the Wessex Formation deposits.

Ancient relative of Velociraptor from “Dinosaur Isle”: Early Cretaceous Dromaeosaurid from the Isle of Wight.

To read about Ceratosuchops inferodios and Riparovenator milnerae: Two New Spinosaurids from the Isle of Wight.

News about the enormous “white rock spinosaurid”: Super-sized Carnivorous Dinosaur from the Isle of Wight.

Everything Dinosaur acknowledges the assistance of a media release from the University of Portsmouth in the compilation of this article.

The scientific paper: “Comptonatus chasei, a new iguanodontian dinosaur from the Lower Cretaceous Wessex Formation of the Isle of Wight, southern England” by Jeremy A. F. Lockwood, David M. Martill and Susannah C. R. Maidment published in the Journal of Systematic Palaeontology.

The Everything Dinosaur website: Dinosaur Models.