Five British dinosaurs you've (probably) never heard of

Think of a dinosaur. It’s likely that the first animals popping into your head were Tyrannosaurus, Diplodocus or Velociraptor, which all hark from the fossil-rich fields of North America and Asia, and are frequent Hollywood stars.

However, although spectacular dinosaur remains have been found all over the world, from Antarctica to Alaska, the UK dinosaur record is often overlooked. This is despite the UK dinosaur record being the most historically important and one that many scientists are still working to unravel.

The first three dinosaurs to receive scientific descriptions, Megalosaurus, Iguanodon and Hylaeosaurus, were all found in the soft sandstones and mudstones of southern England, opening the eyes of scientists and an incredulous public to the existence of past worlds that were populated by animals radically different from anything alive today.

These three were later selected to form the core of a newly recognised group, Dinosauria, which was named in 1842 by prominent anatomist Sir Richard Owen (founder of the Natural History Museum, London). Since then, rocks of Triassic, Jurassic and Cretaceous age from across the UK, with a record spanning from around 220–100 million years ago, have continued to yielded new and important dinosaur fossils, from many corners of the British Isles.

This is the least well-known of the three animals which were used to found Dinosauria, but undeservedly so. Known primarily from a single partial skeleton and a handful of other bones, Hylaeosaurus was a relatively small (3–4 m long) dinosaur and a member of the tank-like armoured group Ankylosauria. In addition to the numerous stud-like bones embedded throughout its skin, its armour also included a series of impressive, curved shoulder spines, all of which would have deterred attacks from most would-be predators.

The remains of Hylaeosaurus were first described in 1833 by Gideon Mantell, a Sussex country doctor who made many of the first dinosaur discoveries. It has the distinction of being the first armoured dinosaur to have been discovered anywhere in the world.

The known specimens all come from Early Cretaceous rocks (~140 million years old) around Cuckfield and Hastings in Sussex, but we have yet to find a complete skeleton. Like other ankylosaurs, Hylaeosaurus was a herbivore that would have browsed on ferns and other low-growing plants and it walked on all fours.

A reconstruction of Hylaeosaurus can be found among the famous statues at Crystal Palace Park in southeast London, although modern reconstructions have updated this image.

Until recently dinosaurs were depicted as lumbering brutes, but vast amounts of new work have overturned this view and revealed them as dynamic, active animals. Nevertheless, a consistent exception to this earlier rule was Hypsilophodon, a bipedal, lightly-built species that has always been regarded as a speedster and the dinosaur equivalent of a gazelle.

Its slender hind legs and long counterbalancing tail anchored powerful muscles, which allowed this small, defenceless animal to outrun and out-manoeuvre most predators. Many skeletons of this dinosaur athlete have been found, providing us with one of the most complete pictures of how small plant-eating dinosaurs looked and behaved.

Hypsilophodon has also been an important animal for understanding the origin and evolution of its later relatives, like Iguanodon and the duck-billed dinosaurs.

Strangely, however, all of the skeletons we have are of youngsters: no adults have been found. All known Hypsilophodon remains come from a single thin layer of sandstone on the Isle of Wight, which dates from the Early Cretaceous period (~125 million years ago). Its currently thought that of these animals belonged to a single herd, which was wiped out in a single tragic event, such as a flash flood or miring in quicksand.

Dinosaurs began their evolutionary journey in the Triassic Period and their earliest definite fossils date from around 230 million years ago. Although the first dinosaurs were rare, small animals, they soon evolved into a number of different types, spreading around the world and experimenting with different lifestyles, behaviours and body types.

Pantydraco is one of the oldest dinosaurs known from the UK, with fossils dating back to the Late Triassic around 210 million years ago. Its fossils come from what is now southern Wales and Bristol, but during the Triassic the area looked quite different with several large islands set in a tropical sea. Pantydraco is a sauropodomorph dinosaur – a member of the same group that went on to include giants like Brachiosaurusand Diplodocus.

Unlike its later relatives, Pantydraco was small (no more than 1.5 m in length), ran on its hind legs and might have eaten both plants and animals. It had a small skull, a long neck and hands that were adapted for grasping, each with a large thumb claw that might have been for defence or to help in gathering food. It is named after the Welsh quarry where the fossils were first found, meaning ‘dragon from Pant-y-ffynnon’.

Most of our knowledge of dinosaur biology is built on bones, using their shapes, sizes and arrangements to reconstruct the animal’s overall appearance, as well as providing many of the clues used to infer important behaviours such as feeding and walking.

However, bones are just one of the many lines of evidence that palaeontologists can use, and other types of dinosaur fossils offer unique and important insights into dinosaur lifestyles, such as footprints or preserved gut contents. Sometimes we are fortunate enough to get the remains of dinosaur skin, which might be either scaly or feathered.

The first dinosaur skin impression found anywhere in the world was discovered in the UK, from the Early Cretaceous rocks of Sussex. It was described in 1852 (again, by Gideon Mantell) and was found together with two large arm bones. Although known from relatively meagre material, these bones are distinctive enough that they can be recognised as a distinct species: Haestasaurus becklesii.

Haestasaurus was a sauropod dinosaur and probably a close relative of animals like Camarasaurus from the USA. The skin impression shows that the body would have been covered with thousands of closely-packed polygonal scales, in an arrangement similar to those of many living reptiles.

In 1983, Bill Walker, an amateur palaeontologist, made a stunning discovery in a Surrey clay pit – the enormous claw of a theropod (meat-eating) dinosaur. The claw was unlike that of any other theropod and further excavation at the site uncovered one of the most complete theropod skeletons ever found in Europe. More surprising was that the new animal belonged to a theropod group that was very poorly known.

Analysis of the fossil showed that it shared many similarities with a famous, but poorly understood, dinosaur from north Africa: Spinosaurus. The new species was named Baryonyx walkeri in honour of its discoverer and the enormous hand claw, which measures 30 cm in length (Baryonyx means ‘heavy claw’).

Like Spinosaurus, Baryonyx has a long, almost crocodile-like snout, which was lined with over 200 conical teeth. These skulls are not adapted for ripping through flesh, as in most other meat-eating dinosaurs, but for impaling more slippery prey, namely fish. The huge claw would have been used to whisk fish from rivers and lakes as Baryonyx prowled through the shallows. We are sure that Baryonyx was a fish-eater for another good reason: in the region where its stomach would have been palaeontologists found a preserved set of partly digested fish scales.

Professor Paul Barrett is a researcher at the Natural History Museum in London, centring on the evolutionary palaeobiology of dinosaurs and other amniotes.

Main image: An artistic representation of Hypsilophodon. © Trustees of the Natural History Museum