Thecodontosaurus
Early herbivorous dinosaur from the late Triassic of England.
Thecodontosaurus, meaning "socket-tooth lizard," was a small, plant-eating dinosaur that belongs to the group of early sauropodomorphs. It lived during the Carnian stage of the late Triassic period. Most of its fossils come from what are called Triassic "fissure fillings" in southern England. This dinosaur walked on two legs, measured roughly 2 meters (about 6.6 feet) long, and ranks among the earliest dinosaurs ever discovered—as well as one of the first to be found by scientists. Over the years, many species were assigned to the genus, but today only the type species, *Thecodontosaurus antiquus*, is considered valid.
The story of its discovery begins in the autumn of 1834, when surgeon Henry Riley and Samuel Stutchbury, curator of the Bristol Institution, started digging up "saurian remains" at a quarry on Durdham Down in Clifton, near Bristol. The site is part of the Magnesian Conglomerate. They gave brief reports in 1834 and 1835, and in 1836 they published the first description, naming the new genus *Thecodontosaurus*. The name comes from Greek words for "socket" and "tooth," referring to the fact that the tooth roots sat in separate sockets rather than being fused to the jawbone, as in modern lizards. *Thecodontosaurus* was the fifth dinosaur ever named, after *Megalosaurus*, *Iguanodon*, *Streptospondylus*, and *Hylaeosaurus*—though Riley and Stutchbury didn’t know it, since the concept of Dinosauria wasn’t introduced until 1842. In 1843, John Morris gave the full species name *Thecodontosaurus antiquus* in his catalogue of British fossils; "antiquus" means "ancient" in Latin.
The original holotype, a lower jaw labeled BCM 1, was destroyed during heavy bombing in World War II, specifically in November 1940 during the Bristol Blitz. However, most of the bones were saved, and today 184 fossil bones are kept at the Bristol City Museum and Art Gallery. Later finds near Bristol at Tytherington added more material. Currently, about 245 fragmentary specimens are known, representing many individuals. In 1985, Peter Galton designated a new neotype, another lower jaw (a right dentary) labeled BCM 2. These remains came from a breccia pocket sitting on Carboniferous Limestone, likely the eroded remains of a Triassic cave.
Quick Facts
- Taxon
- Thecodontosaurus
- Type Species
- Thecodontosaurus antiquus
- Type Species Authority
- Morris, 1843
Facts from the source article.
Lore & Background
In the autumn of 1834, surgeon Henry Riley and curator Samuel Stutchbury began excavating "saurian remains" at Durdham Down, Clifton, near Bristol. They briefly reported the finds in 1834 and 1835, and in 1836 provided the initial description, naming the new genus Thecodontosaurus. The name derives from Greek words meaning "socket" and "tooth," referencing the teeth being set in separate sockets. Thecodontosaurus was the fifth dinosaur named, after Megalosaurus, Iguanodon, Streptospondylus, and Hylaeosaurus, though Riley and Stutchbury were unaware of this—the concept of Dinosauria was only created in 1842. In 1843, John Morris gave the complete species name Thecodontosaurus antiquus, with "antiquus" meaning "ancient" in Latin.
The original type specimen, a lower jaw, was destroyed in November 1940 during the Bristol Blitz of World War II. However, most bones were salvaged; today 184 fossil bones are part of the collection of the Bristol City Museum and Art Gallery. Later remains were found near Bristol at Tytherington. Currently about 245 fragmentary specimens are known. In 1985, Peter Galton designated another lower jaw as the neotype. The remains were found in a breccia pocket on Carboniferous Limestone, probably eroded remnants of a Triassic cave. The geomorphological context indicates a late Carnian age.
Various other species were named over time, including Thecodontosaurus platyodon and Thecodontosaurus cylindrodon, but the hypothesis that such carnivorous prosauropods existed has been discredited. Material of Thecodontosaurus was once mistakenly described as the separate genus Agrosaurus macgillivrayi, thought to be the first dinosaur found in Australia, but in 1999 it was discovered the bones were probably mislabelled. Presently, the only valid species is T. antiquus.
Reader's Guide
Thecodontosaurus holds a significant place in paleontology as one of the earliest dinosaurs ever discovered and one of the oldest known. Its discovery in the 1830s predated the formal recognition of Dinosauria, and it was the fifth dinosaur named. The genus provides key insights into the early evolution of sauropodomorphs, the group that later gave rise to giant long-necked herbivores. Although fragmentary, the remains allow reconstruction of most of the skeleton except the front of the skull. Thecodontosaurus was a small, bipedal herbivore with a short neck, large skull, leaf-shaped teeth, and long tail. Its hands and feet each had five digits, and its front limbs were much shorter than the legs. Studies suggest it was exclusively bipedal and an extremely fast runner, likely to escape predators. The existence of a robust morph in the population may indicate sexual dimorphism. Its small size has been explained as insular dwarfism. Thecodontosaurus continues to be studied for its basal position among sauropodomorphs, possibly preceding the split between prosauropods and sauropods.
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