The American Alligator and the American Crocodile are the native species in the order Crocodilian. The group has not changed much for over 200 million years. They share the same lineage that birds do. Crocodilians are the only reptile order that has a complete secondary palate, which allows it to eat and breath at the same time. At one time, the American Alligator was on the Endangered Species list, but has made a remarkable comeback with federal protection. The American Crocodile is still on the endangered species list. All Crocodilians use temperature-dependent sex determination (TSD), at lower temperatures, eggs develop into females and at high temperatures they develop into males. This is reversed in turtles.

Lizards belong in the order Squamata, this order also includes snakes. All except one species of Texas lizards have legs. The U.S. has two families of geckos, Gekkonidae and Eublepharidae, the former is a introduced species. The family Crotaphytidae are known for their bipedal locomotion, they can run on their saltatorial hindlegs when extra speed is needed. The family Phrynosomatidae contains the common fence & prairie lizards and the well known Horned Lizards. The common Green Anoles are the the family Polychrotidae, along with the introduced Brown Anole. Other families are Scincidae, Teiidae and Anguidae, which contains the Slender Glass Lizards & Alligator Lizards.

Snakes are just highly specialized lizards, most native snakes lack pectoral and pelvic girdles, they have one long right lung, with a reduced right lung. Snakes are the most numerous native reptiles species. Although they all share a similar body shape, they are one of the most interesting vertebrates. They vary in size from the tiny Plains Blind Snake (Leptotyphlops d. dulcis) to the enormous Bull Snake (Pituophis catenifer sayi). Snakes eat anything from spiders to other snakes, live anywhere from aquatic to subterranean environments, reproduce either by laying eggs or giving birth to live young. The sex of the young are determined by chromosomes, and not by temperature.

Turtles are a very unique order of Reptiles, besides the fact that they have a shell, their skull does not have any temporal openings. Mammals have a pair of lateral temporal openings, Lizards, Tuataras, Amphisbaenids, Crocodilians and Birds have a pair of dorsal and lateral temporal openings. Native turtles can be found from dry brushland to marine habitats. Spiny Softshell Turtles (Apalone spinifera) have a soft shell, while the Three-toed Box Turtles (Terrapene carolina triunguis) have a hard, dome like shell that can be closed by hinges on the plastron. All turtles are toothless, lay eggs, have internal fertilization and temperature-dependent sex determination in eggs.