Lessemsauridae
Early sauropodiform clade with flexed forelimbs and large size.
Lessemsauridae is a family of early sauropodiform dinosaurs known from the Triassic and Jurassic of Argentina, South Africa, and possibly Lesotho. The group was identified in a 2018 study by Apaldetti and colleagues, which linked the genera *Lessemsaurus*, *Antetonitrus*, and *Ingentia* through phylogenetic analysis. As a node-based clade, it includes all descendants of the last common ancestor of *Lessemsaurus sauropoides* and *Antetonitrus ingenipes*. Depending on how Sauropoda is defined, Lessemsauridae sits either among the most basal sauropods or as a sister group to Sauropoda. Later in 2018, *Ledumahadi* was added to the family, and a 2021 study by Pol and colleagues also placed *Kholumolumo* and *Meroktenos* within it.
These dinosaurs were quadrupeds. Unlike later sauropods with columnar limbs, lessemsaurids kept their forelimbs bent. Sauropodomorph trackways with widely spaced front feet suggest they were made by animals with flexed forelimbs, matching the lessemsaurid condition. Some lessemsaurids grew very large: *Lessemsaurus* likely weighed about 7 tonnes, and the later *Ledumahadi* may have reached 12 tonnes. Their vertebrae in the neck and back were highly pneumatic, and their neck vertebrae were short from front to back but tall and robust. They also had a greatly expanded lower shoulder blade and upright arms.
Lessemsaurids first appeared in the middle Norian stage of the Triassic. An unnamed specimen from South Africa’s Elliot Formation dates to roughly 218 million years ago. *Lessemsaurus* comes from the La Esquina Local Fauna, which is probably at least 213 million years old. *Antetonitrus* and *Ledumahadi* are found in the Upper Elliot Formation, dating to the Hettangian and Sinemurian stages of the Jurassic. Known fossils come from South Africa and Argentina.
Quick Facts
- Taxon
- Lessemsauridae
Facts from the source article.
Lore & Background
Lessemsaurids were quadrupedal dinosaurs. Unlike later sauropods, which had columnar limbs, the forelimbs of lessemsaurids were flexed. Sauropodomorph trackways with widely-spaced front feet have been found, indicating they were made by a trackmaker with flexed forelimbs as in lessemsaurids. They could reach large sizes: Lessemsaurus was estimated to have reached a mass of 7 tonnes, and the later Ledumahadi reached an estimated 12 tonnes.
Reader's Guide
Lessemsauridae represents a significant early branch in sauropodiform evolution, providing insight into the transition from basal saurischians to the giant sauropods. Their flexed forelimbs contrast with the columnar limbs of later sauropods, suggesting a different mode of locomotion. The clade's large body sizes—with Lessemsaurus at 7 tonnes and Ledumahadi at 12 tonnes—demonstrate that gigantism appeared early in sauropodiform history. The phylogenetic position of Lessemsauridae is debated: it is either among the most basal sauropods or a sister group to Sauropoda, depending on how Sauropoda is defined. Their fossils are known from Argentina and South Africa, indicating a Gondwanan distribution during the Late Triassic and Early Jurassic. The clade was formally named in 2018, with additional members (Ledumahadi, Kholumolumo, Meroktenos) assigned later. Their highly pneumatic vertebrae and robust cervicals are distinctive features. The trackways attributed to flexed-forelimb trackmakers further support the interpretation of lessemsaurid locomotion.
Did You Know?
- Lessemsauridae was named in a 2018 phylogenetic analysis by Apaldetti and colleagues.
- Lessemsaurids had flexed forelimbs, unlike the columnar limbs of later sauropods.
- A specimen of an unnamed lessemsaurid from South Africa probably dates to approximately 218 million years ago.
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