Reptiles

The First True Terrestrial Tetrapods

# of Species of Reptiles

Species Numbers by Higher Taxa:Amphisbaenia (amphisbaenians) 165Sauria (lizards) 4765Serpentes (snakes) 2978Testudines (turtles) 307Crocodylia (crocodiles) 23Rhynchocephalia (tuataras) 2Reptiles total 8240

Reptile Characteristics• Ectothermic• Dry skin covered in scales• Most have 2 pairs of short legs & clawed feet• Oviparous reproduction (Internal fertilization – to avoid

desiccation of gametes)• Eggs have a leathery shell and yolk (amniotic)• Lungs to breathe• 3 or 4 chambered heart• No metamorphosis (young look like miniature parent)• Hibernate & aestivate

Ectothermy

– Body temperature regulated by ambient air temperature

Dry Scaly Skin

The body of reptiles is covered with horny epidermal scales to reduce water loss and provide protection.

Reptile Legs

• Short tetrapods for walking

• Positioning of the legs more directly under the animal. This position provided more support than the splayed arrangement of the Amphibian legs.

Paired Limbs• The paired limbs usually have five toes

and are variously adapted for:• Swimming• Running• Climbing• (Absent altogether in the snakes)

Oviparous

• Amniotic eggs have a leathery shell to prevent desiccation

Amniotic Egg

Amniotic Egg Structures & Functions

• Chorion provides a special hard covering that is permeable to respiratory gases (O2 and CO2) while being impermeable to water vapor.

• Allantois is a storage reservoir for metabolic waste products such as nitrogenous compounds.

• Amnion is a fluid filled sac that acts as a cushion for the embryo and also prevents desiccation.

• Yolk sac contains food for the embryo, thus eliminating the need for a larval stage.

Reptile Lungs

• Respiration is no longer through the skin, but only through internally protected and moistened lungs.

• They have a much greater surface area for the exchange of gases.

• They are inflated and deflated by the expansion & contraction of the rib cage.

Reptile Hearts

• Reptiles have a 3-chambered heart

• Crocodiles have a 4-chambered heart

Excretory Waste

• The excretory waste of the reptiles is uric acid unlike the dilute, water wasting ammonia in the urine of Amphibians.

Family AmphisbaenidaeFamily Amphisbaenidae (Worm Lizards)(Worm Lizards)

• Size: The total body length ranges from 10 cm to about 70 cm.

• Distribution: Mostly Africa & South America with a few species in Europe and North America.

• Habitat: Soil.

• Reproduction: usually oviparous, but some are live-bearing

Lizard Anatomy

Lizard Reproduction

Hatchling Komodo Dragon

Snake Anatomy

Jacobson’s Organ

Snake Reproduction

Turtle Anatomy

Turtle Shell Anatomy

Turtle Shell Anatomy

Fusion of ribs, vertebrae, & carapace

Turtle Life Cycle

Turtle Reproduction

                                                               

Crocodilians

• Crocodiles, Alligators, Caimans, & Gavials

Gavial

Alligator

Crocodile

Caiman

• The temperature inside the nest of several crocodilian species decides the sex of the young. ~50-80 eggs

• If the nest temperature is 30ºC, females will hatch from all the eggs

• If the temperature is above 34ºC, all will be males.

• If the temperature is in between, there will be young of both sexes.

Crocodilian Reproduction