Heterodontosaurus

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Heterodontosaurus
Temporal range: Early Jurassic, 199–196Ma
Iziki Heterodontosaurus fossil.JPG
Cast of SAM-PK-K1332 in Cape Town
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Family: Heterodontosauridae
Subfamily: Heterodontosaurinae
Genus: Heterodontosaurus
Crompton & Charig, 1962
Species
  • H. tucki Crompton & Charig, 1962 (type)

Heterodontosaurus (meaning "different toothed lizard") is a genus of small herbivorous dinosaur with prominent canine teeth which lived in the Early Jurassic of South Africa. It was similar to a hypsilophodont in shape, and ate plants, despite its canines.[1]

Description[edit]

Skeletal restoration

Heterodontosaurus was a small, fleetfooted ornithischian that reached a maximum size of about 3 feet. It had a long, narrow pelvis and a pubis which resembled those possessed by more advanced ornithischians.[1][2]

More unusual was that the hand of Heterodontosaurus had five fingers, two of which seem to be opposable. This configuration allowed Heterodontosaurus to grasp and manipulate food. The bone in the foot and ankle were fused in a manner reminiscent of those in birds.[1][2]

Dentition[edit]

Restored skull

Another interesting feature is the specialization of teeth which gave rise to the animal's name. Most dinosaurs (and indeed most reptiles) have a single type of tooth in their jaws, while Heterodontosaurus had three. At the front of the jaw beside the beak were small teeth likely used for chopping off leaves and stems.[1][2]

Next in the jaw was a large pair of tusks whose purpose is unknown, but it is speculated that they were used as sexual displays (where the tusks could have been used as weapons by rival males in disputes over mates and territories) or to break open prehistoric termite mounds. The final type of teeth were tall and squared off. This type of teeth was well adapted for chewing. Fleshy cheeks helped keep the food in the mouth while chewing occurred.[1][2] Chewing is relatively common in dinosaurs, but uncommon for other groups of reptiles.

This bizarre suite of teeth has led to debate over what heterodontosaurs ate. Some scientists think heterodontosaurs were omnivores who used their differently-shaped teeth to eat both plants and small animals.[1][3]

Discovery[edit]

Heterodontosaurus is currently known from specimens of the SAFM (South African Museum) from South Africa. There are two known morphologies of this genus, the second of which is thought by some to represent a different species. The type species, H. tucki, is from the Upper Elliot Formation of the Hettangian age, around 199-196 million years ago.

Classification[edit]

Timelapse of the construction of a model of H. tucki

The cladogram below follows the analysis by Butler et al., 2011:[4]

Heterodontosauridae 

Echinodon



Abrictosaurus





NHM RU A100



Heterodontosaurus



Lycorhinus





Fruitadens



Tianyulong





References[edit]

  1. ^ a b c d e f Benton, Michael J. (2012). Prehistoric Life. Edinburgh, Scotland: Dorling Kindersley. p. 271. ISBN 978-0-7566-9910-9. 
  2. ^ a b c d "Heterodontosaurus." In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. The Age of Dinosaurs. Publications International, LTD. p. 37. ISBN 0-7853-0443-6.
  3. ^ Tiny Juvenile Dinosaur Fossil Sheds Light on Evolution of Plant Eaters Newswise, Retrieved on October 23, 2008.
  4. ^ Richard J. Butler, Jin Liyong, Chen Jun, Pascal Godefroit (2011). "The postcranial osteology and phylogenetic position of the small ornithischian dinosaur Changchunsaurus parvus from the Quantou Formation (Cretaceous: Aptian–Cenomanian) of Jilin Province, north-eastern China". Palaeontology 54 (3): 667–683. doi:10.1111/j.1475-4983.2011.01046.x. 
  • Dinosaurs and other prehistoric creatures. edited by Ingrid Cranfield, 2000. Salamander Books, pg 132-135.