Class Reptilia

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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.

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Class Reptilia• Scales

• Amniotic egg

• One occipital condyle

• Ectothermic

• Three chambered heart

– Alligators have 4

• Claws4

Ectothermic

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Common Features• Positioning of legs more

directly under animal (more support).

• Paired limbs with five toes. – Adapted for running,

climbing, swimming.– Absent in snakes.

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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.

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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.

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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.

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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.

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Amniote Egg

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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.

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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.

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Reptile Skulls• Anapsid

– No opening

• Synapsid– One opening

• Diapsid– Two openings

• Euryapsid– One small opening

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Subclass AnapsidaOrder Testudines

• 260 species of turtles/tortoises• Oldest group of reptiles (225

mya)• Protective body shell

– Encases vital organs– Provides some protection to

head/limbs– Composed of bony plates

covered by horny epidermal scales

– 2 parts: upper carapace, lower plastron

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Primitive features

– Loss of body-wall muscles

– Ribs/trunk vertebrae fused to carapace

– Lack teeth; hard beak grab and tear food

Subclass AnapsidaOrder Testudines

• All lay eggs on land.

• Third eyelid = nictitating membrane.

• Longest living vertebrates (100+years in wild)!

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TURTLES & TORTOISES

• Only reptile with shell• Only reptile WITHOUT TEETH

http://www.perlgurl.org/archives/2006/05/hawaiian_honu_the_green_sea_turtle.htmlhttp://www.carcosa.net/jason/blog_images/2005/07/04/african-spurred-tortoise.jpg

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Turtle ShellCarapace

Plastron 21

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Box TurtleTerrapene

• Adapted to live on land– Feet not webbed– High domed shell– Safe

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Red-Eared SliderTrachemys

• Red stripe behind eye

• Live in or near water

– Ponds

– Slow moving water

• Pets

• Carry Salmonella

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Snapping TurtleChelydra

• Live in water

• Lay eggs on land

• Long tail

• Muscular limbs

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Giant TortoiseLifespan 150 Years

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Leatherback Sea Turtle

• 6 feet long• 1,400 pounds

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Diapsids

• Dinosaurs• Snakes• Lizards• Crocodilians• Birds

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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

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Order Rhynchocephalia

• 2 species of Tuatara

• Solitary, nocturnal, burrowing animal

Order Squamata

• Kinetic skull

– Movable joints

• Lizards

• Snakes

• Dinosaurs

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• Most successful, diversified of living reptiles.

• Occur in most habitats of world.

• Lizards: – Legs, eyelids, ear openings– Halves of lower jaw united

Order Squamata

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Geckos

• Small lizards

• Adhesive toe pads

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Gecko Toe Pads

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Wall LizardLacerta

• Color is variable

• Slender body

• Small scales

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AUTOTOMY• Self amputation to escape predators• Can’t regrow• Costly; lose muscle/stored fat

http://www.californiaherps.com/lizards/images/ecprincipis1dn.jpg 37

Texas Horned Lizard• Spines for

protection

• Eats ants

• Endangered species

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Gila Monster

• Poisonous lizard

• Not very aggressive

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Green Iguana

• Ornamental crest

• Five feet long

• Tropical rainforest

– Mexico

– South America

• Omnivores

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Chameleons

• Arboreal - live in trees

• Africa and Madagascar

• Catch insects with tongue

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Komodo Dragon

• Attack and eat humans

• 10 feet long

• 300 pounds

• Indonesia

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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

Snakes• No legs• No external ears• Jacobson’s organ

– Sense smell with aid of tongue

• Cornea of eye protected with a spectacle– transparent membrane

• Skull bones loose – Swallow large prey

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JACOBSON’s ORGAN• An extrasensory organ in the roof of a snake's mouth • Sharpens its sense of smell. • Two hollow, highly sensitive saclike structures • Allows it to track both prey and potential mates

http://www.kwic.com/~pagodavista/schoolhouse/species/herps/snktonge.htm45

HEAT SENSING ORGAN• “Pit" organ located between the eye and the nostril on

each side of the head. • Detects heat given off by warm-blooded prey

http://www.kwic.com/~pagodavista/schoolhouse/species/herps/snktonge.htm46

Swallow Prey

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Constrictors• Wrap around prey and kill by suffocation

• Ex: Boa constrictors

http://www.eastrock.org/brazil/images/bra19.jpg

http://www.thematzats.com/snakes/images/squeeze.gif

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VIPERS• Inject venom with large movable fangs

Ex: rattlesnakes, copperheads, water moccasins

Images from: http://www.worsleyschool.net/science/files/rattle/snakes.html

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ELAPIDS• Inject venom with small fixed (non-movable)

fangs

Ex: cobras, kraits, coral snakes

http://www.kidsturncentral.com/animals/cobra.htm51

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Snake Venom

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Copperhead Agkistrodon

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Cottonmouth or Water Moccasin Agkistrodon

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Western Diamond Backed RattlesnakeCrotalus

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Prairie Rattlesnake Crotalus

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Timber Rattlesnake Crotalus

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Black Rat Snake

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Diamond Backed WatersnakeNerodia

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Green Snake

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Coral Snake

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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

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• 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

Dinosaurs

Dominate animals in Mesozoic Era

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Euryapsid

• Extinct• Ichthyosaurs

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Synapsids

• Pelycosaurs• Dimetrodon

– Mammal like reptile

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Order Crocodilia

• Crocodiles

• Caimans

• Alligators

• Gavials

• Elongated skull

• Four chambered heart

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Alligator

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Caiman

• Elevated eyes

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Gavial

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Alligator

Crocodile

Caiman

Gavial

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The End

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