The oldest known dinosaurs – Lesothosaurus


Another (referring to the first part of the article) old dinosaur was the slightly later Lesothosaurus – the Lesotho lizard. In addition to the typical teeth, the herbivore Lesothosaurus had another feature very characteristic of bird-pelvic (Ornithischia) dinosaurs. A new bone appears at the front of the jaw – usually in the form of a toothless beak. The toes are claws rather than hooves.

As the discoveries in northeastern Argentina, and recently also in Madagascar and Poland (in the Opole region), where the remains of the most primitive reptilian herbivores, Prosauropods (Plateosaurids), were found, the Late Triassic was an important moment in the appearance of dinosaurs. Their remains are not common, but each find is of extraordinary value.

Already 225 million years ago, dinosaurs split into reptilian (Saurischia) and bird-pelvis (Ornithischia). Apparently, they evolved from small reptiles running on two legs. They evolved very rapidly. At first, the greatest improvements to their body were to the hind legs and the improvement of fast yet efficient locomotion.

Lesothosaurus diagnosticus

Lesothosaurus – characteristics

Analysis of Lesothosaurus teeth showed that the Lesothosaurus cut the food with its beak and could not chew it. Studies of tooth wear have shown much less tooth wear than would be expected from a herbivore that ate mostly hard vegetation in arid climates, and concluded that Lesothosaurus was probably an omnivore that ate predominantly small animals. Lesothosaurus was one of the earliest Ornithischia dinosaurs. Lesothosaurus lived probably in groups. The Lesothosaurus did not have any special means of protection from predators; it hid from danger by running.

Lesothosaurus was originally considered an ornithopod. However, the work of Paul Sereno suggested that Lesothosaurus is actually one of the most primitive Ornithischians.


The approximately 2-2.5 meter (6.6 – 8.2 ft) long herbivore dinosaur had an iguana-like, short, flat and small skull, with pointed arrow-shaped teeth, short front legs (with five-fingers), long hind legs and a long tail. The long hind legs indicate that Lesothosaurus could run very quickly. Lesothosaurus was a bipedal dinosaur.

Its remains were found in the Upper Elliot Formation. They are approximately 201 to 199 million years old.

Lesothosaurus diagnosticus

Detailed data / dimensions (size)


  • Length: 2-2.5 m (6.6 – 8.2 ft)
  • Height: 45 cm
  • Weight: 10-20 kg (22-44 lb)
  • Lived: 199-189 million years ago
  • Era: Late Triassic, Early Jurassic
  • Food: low vegetation, maybe small animals
  • Occurrence: Africa (Lesotho, South Africa), South America (Venezuela)


  • Kingdom: Animalia
  • Phylum: Chordata
  • Clade: Dinosauria
  • Order: †Ornithischia
  • Clade: †Genasauria
  • Genus: †Lesothosaurus
  • Species: † Lesothosaurus diagnosticus
  • Synonyms:
    • Fabrosaurus australis Ginsburg, 1964
    • Stormbergia dangershoeki Butler, 2005
Lesothosaurus diagnosticus


Dinosaur Database


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