suspectum, the Gila Monster, is one of
the two lizards in the Helodermatidae Family. The other, its closest
relative, is Heladerma horridum which is the Mexican beaded lizard.
The helodermatidae family is also very close with the Monitor lizards (the
varanidae family). A well known member of the Varanidae family is the
Komodo Dragon, the biggest lizard in the world.
This phlogenetic tree is based off the class Reptilia, which includes the
turtles, lizards, crocodiles, alligators, and snakes. The branching off of
this tree is separating the morphological features of the skull and jaw between
the reptiles. The Helodermatidae family has skulls with postorbital archs
but without the supratemporal arch. You can trace the Helodermatidae
family all the way back the Cretaceous period 65 million years ago.
Fossils history proves that the Helodermatidae family lived during that period.