Reptilia

Damnjanović Ivana

Gambassa

Groups of ReptilesSauria (lizards) Serpentes (snakes) Testudines (turtles) Crocodylia (crocodiles) Rhynchocephalia (tuataras)

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.

Shedding

• Snakes turn old skin (scales, epidermis) inside out when shedding

• Turtles add new layers of keratin under old layers of the plate-like scutes (modified scales)

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)

Reptile Lungs• Respiration is no longer through the skin, but

only through internally protected and moistened lungs.

Reptile Hearts• Reptiles have a 3-chambered heart• Crocodiles have a 4-chambered heart

Nervous System

• Sense organs generally well-developed• Hearing generally poorly developed in most

Excretory Waste

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

Oviparous• Eggs have a leathery

shell to prevent desiccation

Amniotic Egg

Squamata

• “Characterized by scales”

• Lizards, snakes• Most recent products

of reptile evolution• Most successful - 95%

of known living species of reptiles

Squamata

• Lizards began diversifying at time when dinosaurs were near end of their dominance

• Were successful because of adaptability

• Adopt various body forms, occupy various habitats

Lizards

• Very diversified group • Terrestrial, burrowing,

aquatic, arboreal, aerial

• Many familiar groups

Lizards

• Geckos • Mostly small,

nocturnal, with adhesive toe pads (walk anywhere)

• Iguanas • Often bright-colored

New World lizards

Lizards

• Skinks • Elongate bodies

Lizards

• Chameleons• Tongue flicked to

greater distance than body length

Draco volans

Snakes

• 10 cm long up to 10 m long

• Highly specialized body form

Snakes• Rearranged internal

anatomy• Left lung reduced or

absent• Hearing - no obvious

external ear• Sensitive to vibrations

carried in ground

Snake Sense Organs

• Olfaction important, but not in nostrils

• Jacobson’s organs (vomeronasal organs)

• Tongue carries scent particles to organ

Snake Feeding

• Skull, jaws highly specialized for feeding

• Eat prey several times their own diameter

• Non-joined mandibles• Loose skull bones

Snake Feeding

• Venom - toxic concentrations in saliva

• Neurotoxic - blindness, paralysis

• Hemolytic - ruptures blood vessels, cells

Snake Feeding

• King cobra most dangerous, largest (5.5 m) - kill 9,000 people per year

Snake Locomotion

Crocodilia

• Unchanged for 160 million years

• Crocodiles larger, more dangerous than alligators

• Prey drowned, ripped into pieces by rapid rolling

• No natural enemies

Crocodilia

• Oviparous - lay eggs in mass of vegetation

• Guarded by mother• Incubation temperature

determines sex of alligator hatchlings

• Low - females• High - males• 5:1 (M:F) in some areas

Chelonia• Turtles • Very ancient group• Little change in

morphology since Triassic period

Turtle Shell Anatomy

Turtle Life Cycle

Sphenodonta

• Tuatara - single species in New Zealand

• Lizard-like, <66 cm• Lives in burrows• Slow-growing, long-

lived (77 years)