Abrictosaurus

Abrictosaurus was a heterodontosaurid dinosaur from the Lower Jurassic of what is now southern Africa. It was a small bipedal herbivore or omnivore, about 1.2 meters (4 feet) long, and weighing less than 45 kilograms (100 pounds).

Abrictosaurus is usually thought to be the most basal member of the family Heterodontosauridae.Norman D.B. et al. 2004. Basal Ornithopoda. In Weishampel D.B., Dodson P., & Osmolska H. (eds). The Dinosauria. 2nd ed, Berkeley: University of California Press. 393-412Weishampel D.B. & Witmer L.M. 1990. Heterodontosauridae. In: Weishampel D.B., Dodson P., and Osmolska H. The Dinosauria 1st ed, Berkeley: University of California Press. 486-497 Lycorhinus and Heterodontosaurus both had high-crowned cheek teeth, which went over each other in the jaw, making a continuous chewing surface analogous to those of Cretaceous hadrosaurids. Abrictosaurus had more widely-split cheek teeth, with lower crowns, more similar to other early ornithischians. 

The family as a whole has canine-like tusks.Sereno, P.C. 1986. Phylogeny of the bird-hipped dinosaurs (Order Ornithischia). National Geographic Research 2: 234-256. Tusks were clearly present on one of the two specimens of Abrictosaurus. The upper caniniform measured 10.5 millimeters (0.4 inches) high, while the lower reached 17 mm (0.67 in).Thulborn, R.A. 1970. The systematic position of the Triassic ornithischian dinosaur Lycorhinus angustidens. Zoological Journal of the Linnean Society 49: 235-245.Hopson, J.A. 1975. On the generic separation of the ornithischian dinosaurs Lycorhinus and Heterodontosaurus from the Stormberg Series (Upper Triassic) of South Africa. South African Journal of Science 71: 302-305. 

Abrictosaurus had smaller, less powerful forelimbs than Heterodontosaurus and one fewer phalanx bone (finger joint) in both the fourth and fifth digits of the forelimb.Thulborn, R.A. 1974. A new heterodontosaurid dinosaur (Reptilia: Ornithischia) from the Upper Triassic Red Beds of Lesotho. Zoological Journal of the Linnean Society of London. 55: 151-175.

 References 

Category:Dinosaurs of Africa
Category:Heterodontosaurs
Category:Jurassic dinosaurs