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Two new species of spinosaur dinosaurs discovered from the Isle of Wight
Two new species of carnivorous dinosaurs have been discovered from the Isle of Wight.
Named 'riverbank hunter' and the 'hell heron' after the environment in which they would have lived, both were a type of dinosaur known as spinosaurids. They are thought to have roamed what is now the island around 129 million years ago.
The Isle of Wight has revealed two astonishing new species of carnivorous dinosaurs. The finds are important in improving the understanding of the group to which they belong, the spinosaurs, and how these animals spread out across the world.
While remains of these dinosaurs have been found widely, the fossils of spinosaurids are often missing major bones that make it difficult to assess their species. What sets the new finds on the Isle of Wight apart is that significant features, such as the skull and tail, are relatively intact.
Jeremy Lockwood, a PhD student at the Museum who helped discover the fossils, says, 'To find two animals is extraordinary. They're so rare, and spinosaurid material across the world is very fragmentary, so to get substantial amounts of skull material from two animals is amazing.
'Then, to find these were two different species was phenomenal!'
The research, led by scientists from the University of Southampton, was published in Scientific Reports.
Beach combing
The spinosaurids were huge carnivorous dinosaurs that most likely walked on upright. Their massive, crocodile-like jaws show that they mostly ate fish, although other dinosaurs were probably also on the menu.
One of the most famous members of this group is Baryonx walkeri, which was named in 1986. Discovered in a clay pit in Surrey, it is one of the most complete fossils of the group ever discovered. Its naming and classification by Museum scientists Alan Charig and Angela Milner caused a sensation in the 1980s, with its large claws capturing the public imagination.
Since then, fossil fragments have continued to be uncovered from the same layers of rock, known as the Wealden formation, which runs under much of the south of England and the Isle of Wight.
Most of these finds have been teeth, which have usually been attributed to Baryonx. However, some differences in these fossils have led to suggestions they may actually be from unknown spinosaurids.
However, there was little evidence of this until Jeremy and local fossil collector Kai Bailey began to find bones on beaches near Chilton Chine, on the southwest of the Isle of Wight.
'I was present with Kai Bailey on the beach when he picked up the snout of one of these dinosaurs, with nice big teeth in it' says Jeremy. 'He was delighted!
'To find parts of the skull of a theropod is very rare, but a week later he found another snout so we knew we had two animals. We started searching the beach quite regularly, and later I found the back end of the skull and excavated it.'
Bones gradually emerged from the rocks over a four-year period between 2013 and 2017, which Jeremy says is not uncommon.
'This dinosaur, like many on the Isle of Wight, was probably spread over quite a large area,' he says. 'If the skeleton wasn't buried rapidly then it would probably be distributed by predators or natural features like streams.
'Very often, the rocks that have these bones in are being worn away by marine erosion, so it takes quite a long time to come out.'
Over this period, Jeremy regularly returned to the beach, finding part of the tail on one visit. Other fossils from the dinosaurs were found by a variety of other people, with the bones being deposited at the Dinosaur Isle Museum on the Isle of Wight for further study.
Co-existence
The researchers found that the two sets of bones were sufficiently different from other spinosaurids to name not one but two new species, each in their own genus.
The first, Riparovenator milnerae, of which parts of the skull and tail were found, is named 'riverbank hunter' to reflect the fish-eating nature of the dinosaur, while its species name honours Dr Angela Milner.
Meanwhile, Ceratosuchops inferodios, or 'hell-heron horned crocodile-face', is again named for its presumed lifestyle of living in wetlands and due to features of the skull such bony ridges around the eye.
The scientists compared the remains to the family tree of the group and found that they were likely close relatives. Not only that, but they may have lived side-by-side at the same time.
'Both dinosaurs were found on the foreshore and were pretty much together,' says Jeremy. 'One would expect they were contemporaneous and there at the same time.
'It's difficult to say for sure, as one was found loose on the foreshore so we can't confirm they were there on the same day, but the species were around at a similar time.'
The pair may also have been contemporaries of Baryonx, potentially putting three spinosaurids together in the same place. To avoid competing with each other, the dinosaurs may each have lived in different habitats, targeted different prey or have been active at different times.
These new dinosaur species also help researchers piece together the history of the spinosaurids. Their findings suggest that the spinosaurids started out in what was then Europe, before spreading into Africa on a number of occasions and giving rise to species like Suchomimus.
Work to discover more about this diversification of the spinosaurids is underway by the researchers, who also plan to carry out more detailed investigations into both R. milnerae and C. inferodios.
