Lessemsauridae
Extinct clade of dinosaurs From Wikipedia, the free encyclopedia
Lessemsauridae is a clade (family)[1] 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.[2] 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.[3] A 2021 study by Pol and colleagues also assigned the genera Kholumolumo and Meroktenos to the group.[4]
| Lessemsaurids | |
|---|---|
| |
| Skeletal mount of Lessemsaurus | |
| Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Family: | †Lessemsauridae Apaldetti et al., 2018 |
| Genera | |
Description
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, with Lessemsaurus estimated to have reached a mass of 7 tonnes[2] and the later Ledumahadi estimated to have reached a mass of 12 tonnes.[3]
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.[2][3]
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.[6] Lessemsaurus is a member of the La Esquina Local Fauna,[4] which probably dates to at least 213 million years ago.[7] Antetonitrus and Ledumahadi 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.
References
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