Among heterodontosaurids, only Heterodontosaurus itself is known from a complete skeleton.
Fragmentary skeletal remains of Abrictosaurus are known but have not been fully described, while most other heterodontosaurids are known only from jaw fragments and teeth.
Consequently, most heterodontosaurid synapomorphies (defining features) have been described from the teeth and jaw bones.
Heterodontosaurus measured just over 1 meter (3.3 ft) in length, while the fragmentary remains of Lycorhinus may indicate a larger individual.

Tianyulong from China appears to preserve filamentous integument which has been interpreted to be a variant of the proto-feathers found in some theropods.
These filaments include a crest along its tail.
The presence of this filamentous integument has been used to suggest that both ornithischians and saurischians were endothermic.
Among heterodontosaurids, only Heterodontosaurus itself is known from a complete skeleton. Fragmentary skeletal remains of Abrictosaurus are known but have not been fully described, while most other heterodontosaurids are known only from jaw fragments and teeth. Consequently, most heterodontosaurid synapomorphies (defining features) have been described from the teeth and jaw bones. Heterodontosaurus measured just over 1 meter (3.3 ft) in length, while the fragmentary remains of Lycorhinus may indicate a larger individual.
Tianyulong from China appears to preserve filamentous integument which has been interpreted to be a variant of the proto-feathers found in some theropods. These filaments include a crest along its tail. The presence of this filamentous integument has been used to suggest that both ornithischians and saurischians were endothermic.
Heterodontosauridae