Thecodontosaurus
From Greek theke (case, socket), odous (tooth) and sauros (lizard); meaning "socket-tooth lizard", reflecting Riley and Stutchbury's observation that the teeth are set in distinct deep alveoli — a configuration unusual among the reptiles known to them at the time.
Thecodontosaurus is a genus of herbivorous basal sauropodomorph dinosaur that lived during the late Triassic period (Rhaetian age). Its remains are known mostly from Triassic "fissure fillings" in southern England. Thecodontosaurus was a small bipedal animal, about 2 m (6.6 ft) long. It is one of the first dinosaurs to be discovered and is one of the oldest that ever existed. Many species have been named within the genus, but only the type species Thecodontosaurus antiquus is seen as valid today.
Diagnosis
- Postorbital flange absent.
- Maxillary and dentary tooth crowns not recurved, with coarse serrations.
- Extensive muscle scar for the origin of M. triceps brachii caput scapulare on the lateral side of the scapular glenoid lip (autapomorphy).
- Humeral cuboid fossa elaborate, with a bilobate proximal outline and an extensively pitted surface (autapomorphy).
- Brevis fossa and shelf reduced.
- Acetabulum incompletely perforated.
- Femoral trochanteric shelf absent.
- Posterolateral descending process of the tibia anteroposteriorly wide and mediolaterally narrow, not reaching the lateral extent of the anterolateral process (autapomorphy; convergent in Anchisaurus, Eucnemesaurus entaxonis, Aardonyx and sauropods).
Species
Thecodontosaurus antiquus Riley & Stutchbury, 1836
Type species
From Latin antiquus ("ancient"), referring to the great geological age of the Magnesian Conglomerate fauna relative to other reptiles known to Riley and Stutchbury in 1836.
- Neotype
- BRSMG C4529/2 , Bristol City Museum and Art Gallery
- Material
- Left dentary with teeth.
- Horizon
- Rhaetian, Late Triassic , 205.7–201.4 million years ago
- Locality
- Quarry Steps Quarry, Clifton, City of Bristol, United Kingdom
Synonyms
-
Thecodontosaurus cylindrodon junior subjective
Treated by Huene (1908) as a separate species on tooth morphology; sunk into T. antiquus by Galton (1973) and reaffirmed by Galton (2007), who attributed gracile vs. robust morphs to within-population variation rather than two species.
References
-
Riley, H.; Stutchbury, S. (1836). A description of various fossil remains of three distinct saurian animals discovered in the autumn of 1834 in the Magnesian Conglomerate on Durdham-Down, near Bristol. Proceedings of the Geological Society of London 2: 397-399.
Erects Thecodontosaurus and the type species T. antiquus on dentary and tooth material from the Durdham Down fissure fill; one of the first five non-avian dinosaurs ever named.
riley1836a -
Huene, F. V. (1908). Die Dinosaurier der Europäischen Triasformation mit berücksichtigung der Ausseuropäischen vorkommnisse [The dinosaurs of the European Triassic formations with consideration of occurrences outside Europe]. Geologische und Palaeontologische Abhandlungen Suppl. 1(1): 1-419.
Classic European Triassic monograph; recognizes T. antiquus and T. cylindrodon as distinct species (later synonymized by Galton 1973) and places the genus in Thecodontosauridae.
huene1908a -
Galton, P. M. (2007). Notes on the remains of archosaurian reptiles, mostly basal sauropodomorph dinosaurs, from the 1834 fissure fill (Rhaetian, Upper Triassic) at Clifton in Bristol, southwest England. Revue de Paléobiologie 26(2): 505-591.
Comprehensive modern review of the Clifton fissure-fill sauropodomorphs; reaffirms T. cylindrodon as a junior synonym of T. antiquus and erects Asylosaurus on previously confused material.
galton2007a -
Galton, P. M. (1973). On the anatomy and relationships of Efraasia diagnostica (Huene) n. gen., a prosauropod dinosaur (Reptilia: Saurischia) from the Upper Triassic of Germany. Paläontologische Zeitschrift 47(3-4): 229-255. Springer Science and Business Media LLC. doi:10.1007/bf02985709
Reassigned material to Thecodontosaurus antiquus.
galton1973a -
Ballell, A.; Rayfield, E. J.; Benton, M. J. (2020). Osteological redescription of the Late Triassic sauropodomorph dinosaur Thecodontosaurus antiquus based on new material from Tytherington, southwestern England. Journal of Vertebrate Paleontology 40(2): e1770774. doi:10.1080/02724634.2020.1770774
Redescribes the species from over 1,000 Tytherington bones, revises its diagnosis and rejects earlier diagnostic characters, and dates the localities to the Rhaetian.
ballell2020a