Heloderma horridum (Wiegmann 1829) Miocene to the present ~35cm is commonly referred to as the Gila monster. Derived from a sister to Shinisaurus, Gobiderma and Cryptolacerta, Heloderma was a phylogenetic predecessor of Lanthanotus .
The skull of Heloderma had a short, round snout with a small orbit. The lateral and upper temporal fenestrae are confluent and comprise more than half the skull exposing the pterygoid. The parietal is broad and the jugal is robust.
The cervicals are smaller, more like the dorsals. The neural spines are very short and small. The tail is relatively small.
The scapula is small. The forelimbs are larger than the hindlimbs. The manus is nearly symmetrical the medial digits longer than typical and the lateral digits shorter.
The pelvis is likewise small. Pedal digit IV is only slightly longer than III and V is as long as II.