Class Reptilia
contains ~6500 species of crocodiles, turtles, snakes, and lizards, tuatara in Australia
more widespread than the amphibians, which are limited by temperature and moisture
Reptiles are only limited by temperature, found in warmer climates up to southern Canada
General reptilian characteristics:
tetrapods - a few have secondarily lost their limbs (snakes and glass lizards)
have a protective skin covered with reptilian scales of epidermal origin made from keratin - prevents water loss and slows dehydration rates
found in essentially all habitat types
claws usually present on the ends of the digits
have an amniotic egg - the developing embryo is surrounded by an amnion which contains the watery amniotic fluid
shells also present to protect the egg from dessication
all have internal fertilization accomplished by a copulatory organ
hemipenis: outpocketing of the cloaca
tuatara lack a copulatory organ - mate by repressing the cloaca
oviparous, viviparous, or ovoviviparous
ectothermic - cannot control their body T physiologically; must depend on behavioral actions by moving to suitable habitats
most with three-chambered heart but crocodilians with functional four-chambered heart
lung-breathers - no gills or larval stages
Four living Orders of Class Reptilia:
Order Testudinata (Chelonia) - turtles
Order Crocodilia - crocodiles and allies
Order Rhynchocephalia - tuatara
Order Squamata - snakes and lizards
Subdivided into three subclasses
Subclass Anapsida
based on lack of a temoral opening on the side of the skull
only living order Testudinata - turtles
Subclass Diapsida
reptiles with two temporal openings
have radiated into large groups
Archosaurians: advanced lizards with tendencies toward bipedalism; led to development of thecodonts (teeth in sockets) - dinosaurs, pterosaurs, crocodilians
Lepidosaurians: primitive reptiles which developed into Rhynchocephalans and Squamates
Subclass Synapsida - gave rise to mammals
Order Testudinata (Chelonia) - turtles In general, Family Chelydridae - snapping turtles Family Emydidae - freshwater and box turtles Family Kinosternidae - mud and musk turtles
Mud turtles
no white areas on sutures
more rounded plastron
Musk turtles
white areas on plastron
more elongated plastron Family Trionychidae - softshell turtles Order Rhynchocephalia - tuataras
  • Represented only by Sphenodon punctatus and S. guentheri on small islands off the coast of New Zealand
  • primitive lizard-like reptile with two temporal openings
  • premaxillaries somewhat beak-like with teeth fused to the jaw and not replaced throughout life span
  • Order Rhynchocephalia - tuataras Order Squamata - snakes and lizards Suborder Lacertilia: lizards
    Suborder Serpentes: snakes Suborder Lacertilia - Lizards 18 families worldwide, 9 in US, 5 in Texas
    Family Iguanidae - iguanids Family Anguidae - glass lizards Family Teiidae - Family Gekkonidae - geckos Family Scincidae - skinks Suborder Serpentes - Snakes 10 families in the world, 5 in US, 4 in Texas
    Family Boidae - boas and pythons only US family not in Texas Family Leptotyphlopidae - blind snakes Family Elaphidae - cobras, mambas, coral snakes Family Viperidae - pit vipers Family Colubridae - nonvenomous constrictors and rear fanged poisonous snakes Three basic forms of feeding Venom delivery by Order Crocodilia - crocodiles and allies The order generally contains three subfamilies in the family Crocodilia breed via internal fertilization - penis develops off the cloaca