Iguana iguana (Laurenti 1768) [extant] is a charter member of the Iguania, one of the two recognized lizards families. This herbivorous lizard was derived from a sister to the basal squamates, Dalinghosaurus and Lacertulus, and phylogenetically preceded Liushusaurus, Draco and Phrynosoma.

Distinct from Lacertulus, the skull of Iguana has a taller naris on a shorter rostrum. The upper temporal fenestra is further exposed on the occipital plane. The orbit is more nearly circular. The pineal foramen is absent or coincident with the frontal/parietal suture. The frontal-parietal suture is straight and wider than the frontal-nasal suture. The postfrontals are tiny ‘droplets’ at the tips of the frontals.

The cervicals are more robust and fewer number. The caudals have elongated neural spines and chevrons. No gastralia are present.

The scapula and coracoid are more deeply fenestrated.

The pubis and ischium are separated by a large thyroid fenestra. The ilium rises posteriorly.

The Iguania clade is relatively uncontroversial, which is why only three members from that clade are included in this study. The other two are Draco and Phrynosoma.

Here the two traditional squamate clades are joined by a third, now totally extinct. Lacertulus and Huehuecuetzpalli are at the base of the new clade, the Tritosauria or "third lizards". The Tritosauria is defined as Pteranodon, Lacertulus, their last common ancestor and all of its descendants.

At the base of all three clades is Dalinghosaurus. The Dalinghosauria includes Dalinghosaurus, Iguana, their last common ancestor and all of its descendants (in other words all lizards, snakes and pterosaurs).

The complete reptile family tree is here.

Laurenti JN 1768. Specimen Medicum, Exhibens Synopsin Reptilium Emendatum cum
Experimentis Circa Venena et Antidota Reptilium Austriacorum. Wien.

Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.

wiki/Iguana