Thecodontosauridae is a family of basal sauropodomorph dinosaursM.J. Benton, L. Juul, G.W. Storrs and P.M. Galton, (2000), "Anatomy and systematics of the prosauropod dinosaur Thecodontosaurus antiquus from the upper Triassic of southwest England", Journal of Vertebrate Paleontology 20(1): 77-108 that are part of the Bagualosauria, known from fossil remains found exclusively in the Magnesian Conglomerate of Bristol, England,Magnesian Conglomerate in the Paleobiology Database which has been traditionally considered to date back to the Rhaetian stage of the Late Triassic. However, other studies have challenged this and suggested a much older date extending back to the Carnian (Other publications have suggested alternative dates ranging from the Norian stage of the Late Triassic to as young as the Hettangian stage of the Early Jurassic). Two genera are known: AgrosaurusSeeley. H. G. (1891). On Agrosaurus macgillivrayi (Seeley), a saurischian reptile from the N.E. coast of Australia. Quarterly Journal of the Geological Society of London 47:164-165 and Thecodontosaurus;Riley, H., and 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 the former is often considered to be the same animal as the latter.
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