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Sunday, 5 June 2011

Scelidosaurus: the Dorset Dinosaur

The cliffs around Lyme Regis contain a lot of fossils from the early Jurassic period, but not many of these are dinosaurs. An important exception is Scelidosaurus, which was one of the earliest dinosaur species -- a large, armour-plated plant-eater similar in appearance to the later Stegosaurus and Ankylosaurus. The short stretch of Dorset coast between Lyme Regis and Charmouth is the only place in the world where Scelidosaur specimens -- about eight of them -- have been identified with certainty (some bones from Arizona were identified as a possible Scelidosaur, but this is far from certain).

Most of the fossils around Lyme come from marine species like ichthyosaurs and ammonites... for the simple reason that the area was part of a shallow sea at the time the rocks were formed. So what was a land-dwelling Scelidosaur doing in Lyme Regis? Probably drowning! It's thought that a small group of Scelidosaurs were swept into the sea by a flash flood. This would explain the complete nature of many of the skeletons... carcasses that had rotted on land and been scavenged would be far less complete. Further evidence that several animals were swept into the sea at once is that most of the skeletons found have come from one layer in the cliffs.

The name Scelidosaurus (meaning leg-lizard) was coined by Sir Richard Owen, who first described the creature in 1859 (some of the bones he described can be seen in Lyme Regis Museum). The most complete Scelidosaur specimen was discovered between Charmouth and Lyme by local fossil collector David Sole in December 2000. It had been preserved in limestone nodules and was recovered over a period of years by careful collecting. The bones were then removed with acetic acid from their encasing rock by Dave Costin of Lyme Regis. A cast of the nearly complete specimen is on display at the Charmouth Heritage Coast Centre, as illustrated below.
[Thanks to our Education Officer Chris Andrew for providing the information on Scelidosaurus. For more about the palaeontology and geology of Lyme, see the Fossils and Rocks page of the main website.]

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