Size and Weight:
Lesothosaurus dates from a murky time--the early Jurassic period--when the first dinosaurs had just split into the two main dinosaur groups, saurischian ("lizard-hipped") and ornithischian ("bird-hipped") dinosaurs. Some paleontologists say the small, bipedal, plant-eating Lesothosaurus was a very early ornithopod (which would place it firmly in the ornithischian camp), while others maintain that it predated this important split.
Whatever the case, Lesothosaurus isn't the only dinosaur of the early Jurassic that continues to puzzle paleontologists. This may or may not have been the same creature as Fabrosaurus (the remains of which were found much earlier, thus giving the name "Fabrosaurus" precedence if the two genera wind up being merged), and it may also have been ancestral to the equally obscure Xiaosaurus, yet another tiny ornithopod native to Asia.