Lessemsaurids | |
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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 | |
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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 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]
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.