Iguanidae

Lore & Background

The family Iguanidae likely first appeared in the Cenozoic; two previously identified Cretaceous genera (Pristiguana and Pariguana) are now considered unlikely to belong to this family. The subfamily Iguaninae, which contains all modern genera, likely originated in the earliest Paleocene about 62 million years ago. The most basal extant genus, Dipsosaurus, diverged from the rest of Iguaninae during the late Eocene about 38 million years ago, with Brachylophus following about 35 million years ago after its dispersal event to the Pacific. All other modern iguana genera formed in the Neogene period.

Reader's Guide

Iguanidae is significant as a family of lizards that includes well-known species such as the green iguana and chuckwallas, and its members are distributed primarily across the Americas, with one genus (Brachylophus) endemic to Fiji and Tonga. The family's evolutionary history is marked by a likely Cenozoic origin and a complex taxonomy that has been reclassified multiple times. Various classification schemes have been proposed, from informal groupings to formal recognition of subfamilies and families, reflecting ongoing debate among researchers.

Iguanas are notable for their diverse adaptations, including herbivory, arboreal and terrestrial habits, nest-guarding behavior, and reliance on basking for thermoregulation. Their distribution has been influenced by natural rafting events and human introductions via the exotic pet trade. The family's fossil record includes extinct genera such as Lapitiguana and Armandisaurus, while Cretaceous genera once assigned to Iguanidae have been excluded.