Scelidosaurus
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| Scelidosaurus harrisonii Owen, 1859 |
Scelidosaurus (meaning 'limb lizard', from Greek skelos/σκελος meaning 'leg' and saurus/σαυρος meaning 'lizard') was a quadrupedal, heavily plated, plant-eating (herbivorous) dinosaur about 4 metres long. It lived during the Early Jurassic Period and its fossils have been found in both England and in Arizona, United States. Scelidosaurus has been called the earliest complete dinosaur; [1] comparative anatomist Richard Owen described Scelidosaurus in 1859.
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[edit] Classification
Scelidosaurus was an ornithischian and has been classified at different times as an ankylosaur or stegosaur. This debate is still ongoing, although it is now considered by most to be more closely related to ankylosaurids than to stegosaurids and, by extension, a true ankylosaur. Despite its ankylosaur classification, it shared similarities with Stegosaurus, including a heavy body highest at the hips and bony plates down its back.
Scelidosaurus gives its name to the Scelidosauridae, a group of primitive ornithischians close to the ancestry of ankylosaurs and stegosaurs. Aside from Scelidosaurus, other members of the clade include Bienosaurus and possibly Scutellosaurus. The family was erected by Chinese paleontologist Dong Zhiming in 2001 after study of Bienosaurus, which shares close affinities with Scelidosaurus. The Scelidosaurids have been found in Early Jurassic formations, and may have persisted into the Late Jurassic. Their fossils have been found in China, England, and Arizona.
[edit] Description
A full-grown Scelidosaurus was rather small, compared to most other dinosaurs. Some scientists have estimated a length of 4 meters (13 ft.) Scelidosaurus was quadrupedal, with the hindlimbs considerably longer than the forelimbs. It may have reared up on its hind legs to browse on foliage from trees, but its forefeet were as large as its hind feet, indicating a mostly quadrupedal posture. Scelidosaurus had four toes, with the innermost digit being the smallest.
Unlike later ankylosaurs, the skull was low and triangular in shape, longer than it was wide, similar to that of primitive ornithischians. The head of Scelidosaurus was small, and it had a neck that was longer than that of most armored dinosaurs.
Like other thyreophorans, Scelidosaurus was herbivorous, with very small, leaf-shaped cheek teeth suitable for cropping vegetation. Later ankylosaurs had teeth which were not quite as leaf-shaped; it is believed Scelidosaurus chewed with simple up-and-down jaw movements. Unlike later Ankylosaurs, Scelidosaurus still had the five pairs of fenestrae (skull openings) seen in primitive ornithischians.
[edit] Armor
The most obvious feature of Scelidosaurus is its armor, consisting of bony scutes embedded in the skin. These osteoderms were arranged in parallel rows down the animal's body. Osteoderms are also found in the skin of crocodiles, armadillos and some lizards. These osteoderms ranged in both size and shape; most were small, flat plates, but thicker scutes also occurred. The scutes were aligned in regular horizontal rows down the animal's neck, back, and hips, with smaller scutes arranged on the limbs and tail. Compared to later ankylosaurs, Scelidosaurus was lightly armored.
[edit] Discovery and Species
While James Harrison of Charmouth, England was quarrying the cliffs of Black Ven (between Charmouth and Lyme Regis (possibly for raw material for the manufacture of cement), in 1858, he found a few fragmentary fossils of limb bones. He sent them to Professor Richard Owen of the Natural History Museum (originally the British Museum (Natural History), London. These, with later finds from the same spot, revealed a near-complete skeleton. Scelidosaurus was named by Sir Richard Owen in 1859; a complete description did not appear until 1863.
Scelidosaurus Species
- S. harrisonii
[edit] References
- Carpenter, Kenneth (2001). “Phylogenetic Analysis of Ankylosauria”, Carpenter, Kenneth(ed): The Armored Dinosaurs. Indiana University Press, 455–480. ISBN 0-253-33964-2.
- Liddell & Scott (1980). Greek-English Lexicon, Abridged Edition. Oxford University Press, Oxford, UK. ISBN 0-19-910207-4.
