Class Reptilia

• Testudines (around 300 species – Tortoises and Turtles)

• Squamata (around 7,900 species – Snakes, Lizards and amphisbaenids)

• Crocodilia (around 23 species – Alligators, Crocodiles, Caimans and Gharials)

• Sphenodontia — (2 species of Tuataras)

Class Reptilia

Characteristics of Reptiles

• A variety of body shapes that are covered with scales and plates for protection against desiccation and injury.

• Most have paired limbs with five toes except snakes.

• Skeleton is well ossified and well developed.

• Respiration with lungs, reptiles do not have gills like the larval stage of amphibians.

Characteristics of Reptiles

• 3 chambered heart, a four chambered heart in crocodilians

• Efficient water conservation organs and behaviors. An example of well-developed organs include paired kidneys and salt glands.

• Sexes separate with internal fertilization.

• They can give live birth or lay eggs. Reptile eggs have a harder shell that can be buried on land and it won’t dry out, similar to the egg of a bird.

• All reptiles are ectothermic.

Testudines…Turtles and Tortoises

• Turtles evolved longs before there were mammals, birds, lizards or snakes, over 200 million years ago.

Characteristics of Testudines…Turtles and Tortoises

• Their unique shell appeared very early. The top is called the carapace and the bottom is the plastron.

• The dorsal bony carapace(shell) is to protect the species from potential predators but it also helps the turtle buffer tough environmental conditions

The shell of turtles and tortoises

Modifications to the shell over evolutionary time:Making the shell lighter in large land tortoises and water turtlesHinges for closing up tight in some species

The protection of the shell protection results in:The great longevity over ecological time of the order of turtles and tortoisesThe fact that turtles/tortoises are such long-lived individuals

Characteristics of the shell in turtles and tortoises

Modifications to the shell over evolutionary time:• Making the shell lighter in large land tortoises and water turtles• Hinges for closing up tight in some species

The protection of the shell protection results in:• The great longevity over ecological time of the order of turtles and

tortoises• The fact that turtles/tortoises are such long-lived individuals

Characteristics of Testudines

• Lacking teeth, a pronounced keratin-made beak is adapted to tear and hold food.

• Testudines have a varied diet– Omnivorous….box turtle

– Herbivorous…many tortoise species

– Carnivorous…many aquatic species

Characteristics of Testudines

• Limbs are modified to suit the habitat and behavior of species.

• Aquatic animals have flattened paddle-like feet for swimming.

• Land dwelling animals often have elephantine feet for walking on substrate.

Squamata…. Snakes and LizardsThe order of snakes and lizards is the largest of the

reptiles. The differences between snakes and lizards…

Snakes• No legs

• No external ears

• No eyelids

Lizards• Usually have legs, but not all

• Have external ears

• Have eyelids

Sensory Perception in snakes and lizards

• Flicking their forked tongue collects chemical molecules that are brought into the mouth and are inserted into the Jacobson’s organ on the roof of the mouth. This organ analyzes the chemical signals

• Lengthened by extra vertebrate

• Internal organs are modified to allow for such a narrow body plan

• Rapid locomotion with three types of crawling, rectilinear, undulation or side winding

Serpentine body plan, the unique morphology of snakes

Sensory Perception in Snakes

• While snakes do not have external ears, they due have a single earbone allowing them to hear low-frequency sound very well.

• Some diurnal snakes such as black racers track prey by keen eyesight

• Some snakes such as pit vipers and most boas and pythons have “pits” on the side of their face to detect infrared heat rays.

Squamata…the Lizards• Versatile tongue for sensory perception with Jacobson’s organ,

for catching food or as a warning to would be predators• Locomotion usually on land with developed legs. Lizards can

also climb well and many species are arboreal or tree dwelling.• Defense through speed, tail shedding, intimidation and/or

camouflage.• Tail can be voluntarily shed to escape attack. Can regenerate

but at a cost in energy, fat storage and even reproduction

Squamata…the Lizards• Lizards have radiated into a

wide variety of habitats and display an array of behavioral, morphological and physiological adaptations.o Keen eyesight (diurnal activity)

o Water conserving organs (can inhabit deserts)

o Most with legs, some without

o Several venomous species

o Behavioral thermoregulation

Crocodilia…Crocodiles, Alligators and Relatives

Complete separation

of arterial and venous blood

True cerebral cortex

“Third” eyelid as in birds

Position of nostrils and

ears that close when

submerged

Crocodilia…Crocodiles, Alligators and Relatives

• Large compressed tail for

swimming

• Modified appendages

• Complex behaviors such as parental care and communication

What is the difference between alligators and crocodiles?

Coloration Blackish/grey

Snout Wider U-shaped snout

Aggressiveness Less aggressive

Preferred Water Freshwater

Lingual Salt Glands Non-functioning

Habitat Southern U.S. and China

Length of adult 4.3 meters

Nesting Lay eggs in mounds of vegetation surrounding freshwater

Location of dermal pressure receptors Limited to jaws

Teeth of the lower jaw Hidden(cannot be seen when jaw is closed)

Lifespan 30 – 50 years

What is the difference between alligators and crocodiles?

American Saltwater CrocodileColoration Olive green/brownSnout Longer V-shaped snoutAggressiveness More aggressivePreferred Water Brackish/SaltwaterLingual Salt Glands FunctioningLength of adult 5.8 metersHabitat Brackish or Saltwater Range: Africa, Australia, and AmericaNesting Lay their eggs in mud or sandLocation of dermal pressure receptors Over most of the bodyTeeth and lower jaw Visible (teeth of lower jaw can be seen when jaw

is closed)Lifespan 70 – 100 years

Sphenodontia…Tuataras• The tuatara is a living

fossil, having many primitive features similar to fossils over 200 million years old!

• Some of these features are:– A primitive skull– A “third eye” or parietal

eye which is on the top of the skull, complete with lens, cornea and nerves to the brain.

– These animals are only found on a handful of islands north of New Zealand.

“third eye” or parietal eye.

• This eye is positioned on the top of the skull, complete with lens, cornea and nerves to the brain.

Questions???