Lessemsaurus
| Key | Value |
|---|---|
| Name Meaning | “Lessem’s lizard” |
| Location | Argentina |
| Time Period | c. 213 million years ago (Late Triassic) |
| Length | 33 ft (10 m) |
| Weight | 8 tons (7,500 kg) |
| Locomotion | Quadruped |
| Diet | Herbivore |
| Described | 1999 (Bonaparte) |
| Geological Formation(s) | Los Colorados |
| Valid Species | Lessemsaurus sauropoides (type) |
Phylogeny: Dinosauria > Saurischia > Sauropodomorpha > Plateosauria > Massopoda > Sauropodiformes > Sauropoda (?) > Lessemsauridae
Overview: Lessemsaurus may’ve been one of the earliest known sauropod dinosaurs. However, if it did or didn’t belong to the Sauropoda is somewhat debatable. Lessemsaurus itself is the namesake of a family called the Lessemsauridae, which contained other dinosaurs like Ingentia, Antetonitrus, and Ledumahadi. Most members come from either South America or southern Africa and would’ve lived during the Late Triassic. Often, the lessemsaurids are seen as the earliest branching and most basal known lineage within the Sauropoda proper, but other studies classify the group just outside of the Sauropoda, within the larger clade Sauropodiformes. Even if they weren’t true sauropods, it does seem that they were among the sauropodomorphs most closely related to them. This genus, at any rate, was more derived than dinosaurs like Melanorosaurus. Lessemsaurus and its kin show us that sauropodomorphs in general were already growing huge by the end of the Triassic.
Researchers usually put Lessemsaurus at maybe nine or ten meters long, with a weight of eight or more standard tons. While this was far smaller than some of its later relatives, Lessemsaurus was still among the largest land animals of its time. To bear its weight, it stood on all four limbs, unlike its more basal and bipedal relatives. Its legs were sturdy and muscular, but had yet to take on the pillar-like form later seen among most sauropods. Lessemsaurus would’ve had a mix of basal and derived traits, typical for a sauropodomorph of its phylogenetic status. It was a herbivore, eating plants like cycads and conifers. Lessemsaurus is known from the Los Colorados Formation in what is now Argentina, so it lived in a warm, seasonal climate. It had to contend with large predators like Fasolasuchus – a terrestrial crocodile relative. Lessemsaurus was named in honor of Don Lessem, an Argentine writer best known for his scientific works, including those on dinosaurs.