| Lessemsaurids Temporal range: Late Triassic-Early Jurassic, 218–193 Ma PreꞒ Ꞓ O S D C P T J K Pg N | |
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| Skeletal mount of Lessemsaurus | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Family: | †Lessemsauridae Apaldetti et al., 2018 |
| Genera | |
Lessemsauridae is a clade (family) of early sauropodiform dinosaurs that lived in the Triassic and Jurassic of Argentina, South Africa and possibly Lesotho. A phylogenetic analysis performed by Apaldetti and colleagues in 2018 recovered a new clade of sauropodiforms uniting Lessemsaurus, Antetonitrus, and Ingentia which they named Lessemsauridae. It is a node-based taxon, defined as all descendants of the most recent common ancestor of Lessemsaurus sauropoides and Antetonitrus ingenipes. Depending on the definition of Sauropoda, Lessemsauridae is either one of the most basal sauropod taxa, or a sister taxon of Sauropoda. An additional member of the clade was named later in 2018, Ledumahadi. A 2021 study by Pol and colleagues also assigned the genera Kholumolumo and Meroktenos to the group.
Description
Lessemsaurids were quadrupeds. Unlike later sauropods, which had columnar limbs, the forelimbs of lessemsaurids were flexed. Sauropodomorph trackways have been found with widely-spaced front feet, indicating they were made by a trackmaker with flexed forelimbs as in lessemsaurids.
Lessemsaurids could reach large sizes, with Lessemsaurus estimated to have reached a mass of 7 tonnes and the later Ledumahadi estimated to have reached a mass of 12 tonnes.
They had highly pneumatic cervical and dorsal vertebrae, very antero-posteriorly short but tall cervical vertebrae, robust cervicals, a very expanded distal scapula blade, and upright arms.
Evolution and biogeography
Lessemsaurids first appeared during the middle Norian age of the Triassic. A specimen of an unnamed lessemsaurid from the Elliot Formation of South Africa probably dates to approximately 218 million years ago. Lessemsaurus is a member of the La Esquina Local Fauna, which probably dates to at least 213 million years ago. Antetonitrus and Ledumahadi are found in the Upper Elliot Formation, which dates to the Hettangian and Sinemurian ages of the Jurassic. Lessemsaurids are known from South Africa and Argentina.
References
- 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. ISBN 978-3-030-95958-6.
- ^ Apaldetti, C.; Martínez, R. N.; Cerda, I. A.; Pol, D.; Alcober, O. (2018). "An early trend towards gigantism in Triassic sauropodomorph dinosaurs" (PDF). Nature Ecology & Evolution. 2 (8): 1227–1232. Bibcode:2018NatEE...2.1227A. doi:10.1038/s41559-018-0599-y. hdl:11336/89332. PMID 29988169. S2CID 49669597.
- ^ McPhee; et al. (2018). "A Giant Dinosaur from the Earliest Jurassic of South Africa and the Transition to Quadrupedality in Early Sauropodomorphs". Current Biology. 28 (19): 3143–3151.e7. doi:10.1016/j.cub.2018.07.063. PMID 30270189.
- ^ Pol, 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. ISSN 0895-9811. S2CID 233579282.
- Sciscio, Lara; Bordy, Emese M.; Lockley, Martin G.; Abrahams, Miengah (2023-09-28). "Basal sauropodomorph locomotion: ichnological lessons from the Late Triassic trackways of bipeds and quadrupeds (Elliot Formation, main Karoo Basin)". PeerJ. 11: –15970. doi:10.7717/peerj.15970. ISSN 2167-8359. PMC 10542822. PMID 37790620.
- 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.
- Kent, Dennis V.; Santi Malnis, Paula; Colombi, Carina E.; Alcober, Oscar A.; Martínez, Ricardo N. (2014-06-03). "Age constraints on the dispersal of dinosaurs in the Late Triassic from magnetochronology of the Los Colorados Formation (Argentina)". Proceedings of the National Academy of Sciences. 111 (22): 7958–7963. Bibcode:2014PNAS..111.7958K. doi:10.1073/pnas.1402369111. PMC 4050597. PMID 24843149.
- Viglietti, P.A.; McPhee, B.W.; Bordy, E.M.; Sciscio, L.; Barrett, P.M.; Benson, R.B.J.; Wills, S.; Chapelle, K.E.J.; Dollman, K.N.; Mdekazi, C.; Choiniere, J.N. (2020-06-01). "Biostratigraphy of the Massospondylus Assemblage Zone (Stormberg Group, Karoo Supergroup), South Africa". South African Journal of Geology. 123 (2): 249–262. Bibcode:2020SAJG..123..249V. doi:10.25131/sajg.123.0018. eISSN 1996-8590. ISSN 1012-0750. S2CID 225859330. Retrieved 2021-02-17.
| Taxon identifiers | |
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| Lessemsauridae | |
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