KINGDOM ANIMALIA Phylum Chordata Subphylum Vertebrata Class Reptilia

1. KINGDOM ANIMALIAPhylum ChordataSubphylum VertebrataClass Reptilia

2. Vertebrate Classes

3. History • 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.

5. Common Features • Positioning of legs more directly under animal (more support). • Paired limbs with five toes. • Adapted for running, climbing, swimming. • Absent in snakes.

6. 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.

7. Story About the Crocodile Heart 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.

8. 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.

9. 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.

10. Amniote Egg

11. 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.

12. 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.

13. Subclass AnapsidaOrder 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

14. Subclass AnapsidaOrder Testudines • All lay eggs on land. • Third eyelid = nictitating membrane. • Longest living vertebrates (100+years in wild)!

15. 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

16. 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

17. 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