Lessemsaurids were quadrupeds. Unlike later sauropods, which had columnar limbs, the forelimbs of lessemsaurids were flexed.[3] Sauropodomorph trackways have been found with widely-spaced front feet, indicating they were made by a trackmaker with flexed forelimbs as in lessemsaurids.[5]
Lessemsaurids could reach large sizes, withLessemsaurus estimated to have reached a mass of 7 tonnes[2] and the laterLedumahadi estimated to have reached a mass of 12 tonnes.[3]
They had highly pneumaticcervical anddorsal vertebrae, very antero-posteriorly short but tall cervical vertebrae, robust cervicals, a very expanded distalscapula blade, and uprightarms.[2][3]
Lessemsaurids first appeared during the middle Norian age of the Triassic. A specimen of an unnamed lessemsaurid from theElliot Formation of South Africa probably dates to approximately 218 million years ago.[6]Lessemsaurus is a member of the La Esquina Local Fauna,[4] which probably dates to at least 213 million years ago.[7]Antetonitrus andLedumahadi are found in the Upper Elliot Formation, which dates to the Hettangian and Sinemurian ages of the Jurassic.[8] Lessemsaurids are known from South Africa and Argentina.
^Apaldetti, C.; Martínez, R. N. (2022). "South American Non-Gravisaurian Sauropodiformes and the Early Trend Towards Gigantism". In A. Otero; J. L. Carballido; D. Pol (eds.).South American Sauropodomorph Dinosaurs. Springer Earth System Sciences. Springer. pp. 93–130.doi:10.1007/978-3-030-95959-3_3.ISBN978-3-030-95958-6.
^abPol, Diego; Otero, Alejandro; Apaldetti, Cecilia; Martínez, Ricardo N. (2021-01-11). "Triassic sauropodomorph dinosaurs from South America: The origin and diversification of dinosaur dominated herbivorous faunas".Journal of South American Earth Sciences.107 103145.Bibcode:2021JSAES.10703145P.doi:10.1016/j.jsames.2020.103145.ISSN0895-9811.S2CID233579282.
^Moopen, Atashni; Viglietti, Pia A; Choiniere, Jonah N (2023-12-15). "Anatomy and phylogenetic relationships of a possible lessemsaurid with associated plant fossils from the lower part of the Elliot Formation".Palaeontologia Africana.56:190–212.
