More than 160 years after its discovery, the first complete dinosaur skeleton ever identified has been described in great detail. Research from the University of Cambridge, published as four separate studies, reveals what the mysterious dinosaur looked like, as well as where it falls in the family tree.
The dinosaur, known as Scelidosaurus, was recovered from rocks on the infamous Jurassic Coast. These rocks date back about 193 million years to the Mesozoic Era, which is often called the “Age of Dinosaurs.”
The skeleton was initially sent to Richard Owen – the man who invented the word dinosaur – at the British Museum. Owen published two short papers on the anatomy of the specimen, but some of the most important details were not documented. For example, Owen did not reconstruct the skeleton or analyze the relationships of Scelidosaurus with other dinosaurs.
For the past three years, Dr. David Norman has been preparing a detailed description of Scelidosaurus. The work has revealed that it was an early ancestor of Ankylosaurus, an armor-plated herbivore of the Late Cretaceous Period.
For more than 100 years, dinosaurs have been primarily classified according to the shape of their hip bones as either “lizard-hipped” saurischians or “bird-hipped” ornithischians.
However, Dr. Norman and his team proposed that bird-hipped and lizard-hipped dinosaurs evolved from a common ancestor. The researchers also discovered that the first ornithischians appeared in the Early Jurassic Period.
“Scelidosaurus is just such a dinosaur and represents a species that appeared at, or close to, the evolutionary ‘birth’ of the Ornithischia,” said Dr. Norman. “Given that context, what was actually known of Scelidosaurus? The answer is remarkably little!”
“Nobody knew that the skull had horns on its back edge. It had several bones that have never been recognized in any other dinosaur. It’s also clear from the rough texturing of the skull bones that it was, in life, covered by hardened horny scutes, a little bit like the scutes on the surface of the skulls of living turtles. In fact, its entire body was protected by skin that anchored an array of stud-like bony spikes and plates.”
Scelidosaurus was regarded for many years as an early relative of the family that includes Stegosaurus, but the new investigation suggests that the dinosaur is an ancestor of Ankylosaurus alone.
“It is unfortunate that such an important dinosaur, discovered at such a critical time in the early study of dinosaurs, was never properly described,” said Dr. Norman. “It has now – at last! – been described in detail and provides many new and unexpected insights concerning the biology of early dinosaurs and their underlying relationships. It seems a shame that the work was not done earlier but, as they say, better late than never.”
The study is published in the Zoological Journal of the Linnean Society.