KINGDOM ANIMALIA Phylum Chordata Subphylum Vertebrata Class Reptilia
Vertebrate Classes
Reptiles are the evolutionary base for the rest of the tetrapods. Early divergence of mammals from reptilian ancestor. Early reptiles arose from amphibian ancestor and were small, lizard-like insectivores. History
Common Features Positioning of legs more directly under animal (more support). Paired limbs with five toes. Adapted for running, climbing, swimming. Absent in snakes.
Common Features Body covered with horny epidermal scales made from protein keratin. Scales serve to reduce water loss and provide protection. Reptiles molt as they grow. Jaws adapted to biting/tearing.
Common features Respiration through internally protected and moistened (a moist cloacal surface in some turtles). Most reptiles have a 3- chambered heart with a partially divided ventricle. No mixing of blood from lungs with deoxygenated blood. Crocodiles have 4 chambers and a unique feature: cog teeth. Story About the Crocodile Heart
Common features Excretory waste = uric acid (doesn t waste water) Brain = first cerebral cortex (capable of reasoning, planning, perception) Still ectothermic Must live in favorable conditions or hibernate. Being ectothermic enables an organism to survive on much less food than an endothermic organism.
Reproduction Internal fertilization: gametes not subject to desiccation. Amniote egg = significant evolutionary breakthrough. Egg covered by tough, water-resistant, leathery or calcerous shell. Extraembryonic membranes compartmentalize the interior for several functions.
Amniote Egg
Amniote Egg Chorion = hard covering permeable to respiratory gases but not water. Allantois = functions in gas exchange and a storage reservoir for metabolic waste. Amnion = fluid-filled sac acts as cushion for embryo and prevents desiccation. Yolk sac = food for embryo; eliminates need for larval stage.
Reptile Skulls Except for turtles, all reptiles have two temporal openings in the skull. These openings have allowed for attachment and expansion of the jaw muscles.
Subclass Anapsida Order Testudines 260 species of turtles/tortoises Oldest group of reptiles (225 mya) Protective body shell Encases vital organs Provdes some protection to head/limbs Composed of bony plates covered by horny epidermal scales 2 parts: upper carapace, lower plastron Primitve features: Loss of body-wall muscles Ribs/trunk vertebrae fused to carapace Lack teeth/horny beak grab and tear food
Subclass Anapsida Order Testudines All lay eggs on land. Third eyelid = nictitating membrane. Longest living vertebrates (100+years in wild)!
Subclass Diapsida Superorder Lepidosauria Order Squamata 4675+ species of lizard 2700+ species of snakes 140 species of amphisbaenians Limbless, burrowing animals Vestigial eyes under skin Order Rhynchocephalia 2 species of Tuatara Solitary, nocturnal, burrowing animal
Order Squamata Most successful/diversified of living reptiles. Occur in most habitats of world. Snakes: Elongated derivative of lizard (increased vertebrae, not lengthening of segments) Lack limbs, eyelids, ear openings Jaw bones are loosely united to allow swallowing of large prey Throat and windpipe are at separate ends of mouth to allow breathing while eating Can be venomous (hemotoxin/neurotoxin) Tongue to smell, some have heat pits to sense body heat Lizards: Legs, eyelids, ear openings Halves of lower jaw united
Superorder Archosauria Includes extinct dinosaurs/pterosaurs and birds 23 species of crocodiles, alligators, & caimans Largest of the living reptiles Amphibious carnivores Live in tropics/subtropics Lizard-like body with short legs, clawed/webbed toes, massive tail Flat head with nostrils at tip Powerful jaws Dorsal side armored with dermal plates