Heterodontosaurus
Small dinosaur with three types of teeth from Early Jurassic.
Heterodontosaurus was a small dinosaur from the Early Jurassic, around 200 to 190 million years ago. Its only known species, *Heterodontosaurus tucki*, was given its name in 1962 after a skull turned up in South Africa. The genus name translates to "different toothed lizard," a nod to its unusual mix of tooth shapes, while the species name honors G. C. Tuck, who backed the people who found it. More fossils have been uncovered since, including a nearly complete skeleton in 1966. Although small, it was one of the bigger members of its family, measuring somewhere between 1.18 and 1.75 meters long and weighing 2 to 10 kilograms. Its skull was long, narrow, and triangular from the side, with a horny beak at the front of the jaws. It had three kinds of teeth: small incisor-like teeth in the upper jaw, followed by long, canine-like tusks, then a gap before chisel-like cheek teeth. The body was short with a long tail. Its five-fingered forelimbs were long and fairly sturdy, while the hind limbs were long, slender, and ended in four toes.
Heterodontosaurus is the namesake and most familiar member of the family Heterodontosauridae, a group considered basal among ornithischian dinosaurs, though exactly where they fit within that order is still debated. Despite its big tusks, it likely ate plants or at least a mix of plants and meat. Once thought to walk on all fours, it is now believed to have been bipedal. Unlike its relatives, its tooth replacement happened sporadically rather than continuously. At least four other heterodontosaurid genera come from the same rock layers as Heterodontosaurus.
The first specimen, the holotype (SAM-PK-K337), was dug up during a British–South African expedition to South Africa and Basutoland (now Lesotho) in 1961–1962. It now sits in the Iziko South African Museum. It came from a mountain about 1,890 meters high at a site called Tyinindini, in the Transkei district (sometimes called Herschel) of Cape Province. The find was a crushed but nearly complete skull; any postcranial bones mentioned in the original write-up could not be located by 2011. Paleontologists Alfred Walter Crompton and Alan J. Charig described and named the animal in 1962. The specimen wasn't fully prepared when published, so only the front parts of the skull and lower jaw were described, and the authors called it a preliminary description mainly to give the creature
- lived
- Early Jurassic, 200–190 million years ago
- length
- 1.18 m to possibly 1.75 m
- weight
- 2 to 10 kg
- diet
- Herbivorous or at least omnivorous
- locomotion
- Bipedal
- known_for
- Heterodont dentition with three types of teeth
- discovered_in
- South Africa
Lore & Background
The holotype specimen of Heterodontosaurus tucki (SAM-PK-K337) was discovered during the British–South African expedition to South Africa and Basutoland in 1961–1962. It was excavated on a mountain at an altitude of about 1,890 m, at a locality called Tyinindini, in the district of Transkei in the Cape Province of South Africa. The specimen consists of a crushed but nearly complete skull. The animal was scientifically described and named in 1962 by palaeontologists Alfred Walter Crompton and Alan J. Charig. The specimen was not fully prepared by the time of publication, so only the front parts of the skull and lower jaw were described. Preparation was very time consuming because the bones were covered in a thin, very hard, ferruginous layer containing haematite, which could only be removed by a diamond saw, damaging the specimen.
In 1966, a second specimen (SAM-PK-K1332) was discovered at the Voyizane locality, in the Elliot Formation of the Stormberg Group, on Krommespruit Mountain. This specimen included both the skull and skeleton, preserved in articulation with little displacement. The postcranial skeleton was briefly described in 1976, and the skeleton was fully described in 1980. SAM-PK-K1332 is the most complete heterodontosaurid skeleton described to date. The skull was not fully described until 2011 by palaeontologist David B. Norman and colleagues. Other specimens referred to Heterodontosaurus include a juvenile skull, fragmentary maxillae, and a partial snout originally thought to belong to Massospondylus. In 1970, palaeontologist Richard A. Thulborn suggested Heterodontosaurus was a junior synonym of Lycorhinus, but this was disputed by Charig and Crompton and later by palaeontologist James A. Hopson, who defended generic separation.
Reader's Guide
Heterodontosaurus is significant as the best-known member of the Heterodontosauridae, a basal family of ornithischian dinosaurs. Its discovery in the early 1960s was important because few early ornithischian dinosaurs were known at the time. The almost complete skeleton found in 1966 helped establish that Dinosauria was a monophyletic natural group, contrary to the prevailing view that Saurischia and Ornithischia were not directly related. Despite its large tusks, Heterodontosaurus is thought to have been herbivorous or at least omnivorous. It was formerly thought capable of quadrupedal locomotion but is now considered bipedal. Tooth replacement was sporadic and not continuous, unlike its relatives. The family contains some of the smallest known ornithischian dinosaurs, though Heterodontosaurus was among the largest members of its family. At least four other heterodontosaurid genera are known from the same geological formations. The 2016 scanning of a new specimen at the European Synchrotron Radiation Facility has aided research into its anatomy and lifestyle.
Did You Know?
- The genus name Heterodontosaurus means 'different toothed lizard', referring to its three types of teeth: incisor-like, canine-like tusks, and chisel-like cheek-teeth.
- The holotype skull was covered in a hard ferruginous layer containing haematite, which could only be removed with a diamond saw, damaging the specimen.
- A 1966 specimen (SAM-PK-K1332) is the most complete heterodontosaurid skeleton described to date and helped establish that Dinosauria was a monophyletic group.
- In 1970, Heterodontosaurus was suggested to be a junior synonym of Lycorhinus, but this was disputed and later rejected by other palaeontologists.
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