Tupinambis
Tupinambis is a lizard genus which belongs to the family Teiidae and contains eight described species. These large lizards are commonly referred to as tegus (teiús in Portuguese). "T. merianae" (Argentine black and white tegu), "T. rufescens" (red tegu), and "T. teguixin" (gold tegu) are popular in the pet trade. They are primarily found in South America, although "T. teguixin" also occurs in Panama. In 2012, a number of tegu species were reclassified from "Tupinambis" to the previously used genus "Salvator". The newly proposed classification comes from a restructuring of the family Teiidae based upon the study of 137  morphological characteristics. The new classification is as follows: "Salvator duseni" (yellow tegu), "Salvator rufescens" (red tegu), "Salvator merianae" (Argentine black and white tegu), "Tupinambis teguixin" (gold tegu), "Tupinambis longilineus" (Rhondonia tegu), "Tupinambis palustris" (swamp tegu) and "Tupinambis quadrilineatus" (four-lined tegu). Names. "Tupinambis" lizards are called teiú in Portuguese. The lizards are also called tishiriú in the extinct Tuxá language of Bahia, Brazil, and dzižuảsu in the extinct Potiguara language of Pernambuco, Brazil. As with many other animals from tropical South America (e.g. the Cariamae), "Tupinambis" owes its scientific name to the pioneering accounts given by Piso & Marcgrave in their  Historia Naturalis Brasiliae (1648). However, a misinterpretation (by Linnaeus) of the Latin text occurred, which reads "TEIVGVACV [...] Tupinambis", 'to the Tupinambá [Indigenous group] TEIVGVACU'. "Tupinambis" was merely a metalinguistic term meaning 'to/for the Tupinambá,' whereas the intended, indigenous name for the animal was "teiú-guaçú" [lizard-big]; lit. 'big lizard'. Description. The "Tupinambis" species have heterodont dentition consisting of four different types of teeth. Incisor-type—tricuspid—teeth reside at the tip of the mouth. Recurved canine-type teeth occur further back on the tooth row. Behind those reside a separate set of incisor-like teeth (though flattened in  a perpendicular plane to the first set of incisors). The rearmost teeth are blunt, rounded, peg-shaped teeth. The rearmost two tooth classes only occur in sexually mature individuals, thus indicating an ontogenetic shift in tooth morphology. Along with changes in tooth type, the frequency of each tooth type also changes with ontogeny, without an overall change in tooth count (approximately 70 teeth). Rather than increase tooth count, the teeth themselves increase in size as the jaw grows from hatchling to adult. This ontogenetic shift in tooth morphology suggests a shift in diet with age; however, few dietary studies have  been done to support this claim and limited stomach content observations do not show much variability between hatchlings and juveniles. Taxonomy. Species listed alphabetically by specific name. Evolution. Mitochondrial DNA analysis indicates a deep divergence between a northern clade (containing "T. teguixin", "T. palustris" and "T. quadrilineatus") and a southern clade (containing "T. duseni"). The northern and southern clades are morphologically distinct, with the northern clade possessing a single pair of loreal scales between the eye and the nostril and a smooth texture to the scales on the body and the southern clade possessing two pairs of loreal scales and  a bumpy texture to the scales on the body. At least one review of the morphology of the family Teiidae has placed the tegus of the southern clade in the genus "Salvator." Subsequent studies support the paraphyletic status of "Tupinambis", though further research will be necessary to determine if the split will gain wider acceptance among the herpetological community. Comparative analysis of hemipenial anatomy also provides support for the split between "Tupinambis" and "Salvator". Tegus probably originated sometime during the Cenozoic era. "Tupinambis" fossils from Argentina date back to the Late Miocene. Fossils of the extinct tegu "Paradracaena" can be  found in earlier Miocene deposits.