A Galapagos land iguana, Conolophus subcristatus, photographed by David Benson.

The family Iguanidae has been subjected to many taxonomic discussions and rearrangements since 1989. At that time, two herpetologists, Frost & Etheridge, divided the large family as it was traditionally known into several smaller families. Previously, these small families had been ranked as subfamilies. Nearly a decade later, molecular systematists argued that a single large Iguanidae was indeed justified. While the debate continues, we herein regard the traditional Iguanidae as such, because there is considerable evidence to support such recognition, and because such recognition simplifies the taxonomy of the group.

Iguanids are lizards with important ancestral features: all have four limbs with five clawed digits, moveable eyelids, and pleurodont teeth. Most are capable of regrowing a lost tail (autotomy), and nearly all have an external ear opening.

The large iguanids, including the green iguanas, marine and land iguanas, chuckwallas, spiny-tailed and Caribbean iguanas are primarily herbivorous. Smaller iguanids, including collared and leopard lizards, earless lizards, swifts and the huge anoline group, are largely insectivorous.

Iguanids are primarily diurnal, and possess a distinct dorsal pineal eye. They display a great variety of crests, frills, and spines among their members, and dwell in forests, deserts, grasslands and the ocean. Iguanids are almost exclusively restricted to the Americas, but there are odd extralimital genera in the Fiji Islands and on Madagascar.

Literature:

Frost, Daryl and Richard Etheridge. 1989. A phylogenetic analysis and taxonomy of iguanian lizards (Reptilia: Squamata). University of Kansas Museum of Natural History Miscellaneous Publications 81: 1-65.

Macey, J. R.,  Allan Larson, Natalia Ananjeva and Theodore Papenfuss. 1997. Evolutionary shifts in three major structural features of the mitochondrial genome among iguanian lizards. Journal of Molecular Evolution 44: 660-674.

Sprackland, Robert. 1999. Iguanids, iguanines, and drawing lines. The Vivarium 10(2): 24-25.