Reptiles

General Characteristics

1. Amniotic egg – shelled2. Internal fertilization3. Scales or plates4. If legs – 2 pair with claws5. Well developed lungs6. Ectothermic – don’t generate their

own body heat

Importance of the AmnionAmphibians had to lay their eggs in water

to prevent them from drying out and killing the embryo inside.

With the advance of the reptilian egg with its leathery outer shell and amniotic sac, now the animal could live its life fully on land without fear that its eggs would dry out as the embryo developed inside.

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Taxonomic BreakdownKingdom –

AnimaliaPhylum –

ChordataClass –

Reptilia

Order Testudines

Order Chelonia or TestudinesTurtle – sea turtles

230 speciesWebbed feetSoft-shelled (streamlines)Omnivorous – eat both plants and animals

Order Chelonia or testudinesTerrapin – fresh water turtles

Claws and webbed feetSymmetrical plates called scutes covering bony under

layers Top shell – carapaceBottom shell – plastron or parapace

Order Chelonia or testudines Tortoise – land turtle

Long necks, short limbsAppendages completely drawn into shell, if not – very aggressiveNo teethTympanic membrane (poor hearing) Nicitating membrane (3rd eyelid)Good sense of smell, good color visionTemperature determines sex of eggs: low temp = males

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Order Squamata

Order Squamata – Lizards/Snakes Iguanas – horned toad, anoles (chameleons) change color

in response to light, temperature, and mood True chamelons – arboreal (tree dwelling); tongue longer

than body

Skinks – shiny cylindrical body, weak legs, tails fall off when grabbed

Gila Monster (aka Beaded Lizard) – only poisonous lizard known to the world Native to the desert southwest of the US and MexicPoison is found in saliva… no fangsThe poison is a nerve toxin, that is produced in glands located in

the lower jaw. When a Gila Monster bites an animal, the poison flows into the wound via grooved teeth. This poison only rarely kills people.

Gila MonsterBeaded Lizard

Gecko (Geico?) – most primitive; pads on toes to cling; makes noises, insectivores, eye has vertical pupil to see at night

Monitor – Komodo dragon is largest = 10 feetFYI: The Komodo dragon is not venomous or

poisonous; however, its saliva contains a number of toxic strains of bacteria which often infect the wounds inflicted on its prey, causing death.

Snakes

Loss of limbs and external earsEvolved from lizardsMost numerous reptile2,800 species (300 poisonous)

Snake Anatomy

Long, thin – head, trunk, tail Scales and scutes

Protect skinPrevent water lossMolting or ecdysis

SkeletonFlexible spine of 150 vertebrae1 pair ribs attached to each

vertebrae

Snake Systems• Respiratory – 1 well developed right lung; left missing• Circulatory – 3 chambered heart; partially divided ventricle• All organs long and thin and lie alternating, not side by side

Snake Movementhttp://www.ucs.louisiana.edu/~brm2286/locomotn.htm

Lateral undulation – crawling quickly or swimming, s-shaped motion, most common

Rectilinear locomotion– straight movement, no lateral movement, used by large snakes

Sidewinding – twists into loops and touches ground at 2-3 points; used by desert dwelling snakes or on slippery surfaces

Concertina locomotion– pulling up the body into bends and then straightening out the body forward, used in crawling through tunnels or narrow passages

Snake Sense Organs

Internal ear – low frequency; sensitive to vibrations Acute sense of smell

Jacobson’s organ – roof of mouthTongue picks up scent particles and inserts into Jacobson’s organTongue is forked shaped to sense the direction of the smells

Snake Sense OrgansSightCornea – permanently protected with spectacleMost have poor vision with exception of the

arboreal (tree dwelling) snakes

Snake FeedingCarnivorousKills via: Poison or constrictionSwallow food whole

Jaw comes unhingedElastic ligamentsGlottis moves forward (so can breathe while

swallowing)Large esophagusNo sternumStrong stomach acid

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Swallow Prey

Non poisonous snakesGarter snakeBlack snakeKing snakeBoa constrictor

Poisonous SnakesVipers

Rattlesnakes, copperheads, adderHeat sensitive pits on head (pit vipers)Long thin fangs – fold up when mouth is closed

Rattlesnake

Copperhead

Puff Adder

Elapsids (cause swelling of lymph nodes)Cobras, coral, kraitsPermanently erect fangs (short) Hydrophiidae (family) – sea snakes

Highly poisonous – nonaggressiveColubridae (family, both non and poisonous) – African

boomslang and twig snakes rear fanged

Cobra Coral SnakeKrait

Top Ten Most Deadly Snakes1) Fierce Snake or Inland Taipan (Oxyuranus microlepidotus ), Australia. The most toxic

venom of any snake. Maximum yield recorded (for one bite) is 110mg. That would probably be enough to kill over 100 people or 250,000 mice. These rare snakes are virtually unknown in collections outside of Australia.

2) Australian Brown Snake (Pseudonaja textilis ), Australia. One 1/14,000 of an ounce of this venom is enough to kill a person.

3) Malayan Krait (Bungarus candidus ), Southeast Asia and Indonesia. 50% of the bites from this snake are fatal even with the use of antivenin treatment.

4) Taipan (Oxyuranus scutellatus ), Australia. The venom delivered in a single Taipan bite is enough to kill up to 12,000 guinea pigs.

5) Tiger Snake (Notechis scutatus ), Australia. The Tiger snake is a very aggressive snake that kills more people in Australia that any other snake on that continent.

6) Beaked Sea Snake (Enhydrina schistosa ), South Asian waters Arabian Sea to Coral Sea..7) Saw Scaled Viper (Echis carinatus ), Middle East Asia. Saw Scaled Vipers kill more people in

Africa that all the other venomous African snakes combined. Its venom is 5 times more toxic than that of the cobra and 16 more toxic than the Russell's Viper.

8) Coral Snake (Micrurus fulvius ), North America. Coral Snakes have a very potent venom but many are too small to deliver enough venom to kill a human. This is the only elapid (relative of the cobras and mambas) in the US.

9) Boomslang (Dispholidus typus ), Africa. The Boomslang is the most seriously venomous rear-fanged snake in the world. They have very long fangs and can open their mouths a full 180 degrees to bite. Famous herpetologist Karl P. Schmidt died 28 hours after a Boomslang bite. The day after the bite, he called in to say he felt well and would be in to work...2 hours before he literally dropped dead from the bite.

10) Death Adder (Acanthophis antarcticus ), Australia and New Guinea. The Death Adder looks like a viper but is more closely related to the cobras. A dosage of 10mg of Death Adder venom is enough to kill a human. A good sized Death Adder can deliver up to 180mg in a single bite.

Snake Venom

Snake VenomNeurotoxin – affect nervous systemHemotoxin or hemmoragin – affects red blood cellsAll contain both types, the amounts of each may

differDanger is in the amount and concentration of

injected venomWhere:

In blood vessel… spread fastIn muscle or fat… spread slow

Snake ReproductionOviparous – lay eggsOviviparous – retain

eggs in body, born aliveViviparous – primitive

placenta forms; receives nourishment from mother (rare)

Order Crocodilia

Order CrocodilianCarnivorous 4 chambered heartRaised nostrils and eyes (so rest of body is

underwater) Valve at back of mouth prevents water

from entering lungs when mouth is openTeeth in sockets (thecodont)

Eyesight in ReptilesMost reptiles are sight hunters, and can see

in color both during the day and at night. Most reptiles have both an upper and lower eyelid along with a nictitating membrane.

Some reptiles even have a third eye in the middle of their forehead called a median eye or a parietal eye. The tuatara’s parietal eye can actually see, but in most lizards it is barely noticeable and can only detect light and dark.

Order CrocodilianDifferences Between Alligators and Crocodiles

Alligators Crocodiles

Less aggressive More aggressive

More terrestrial More aquatic

Rectangular head Triangular head

Teeth not visible when mouth is closed

Teeth visible when mouth is closed

Definite vocalizations No definite vocalizations

Order CrocodilianBoth Alligators and Crocodiles are…

Oviparous (egg-laying)Guard nest and care for youngAs with many turtles and some lizards – temperature

of nest determines sex of youngLow temperature = females

Hearing & SmellingAll reptiles can hear, but some hear better

than others; for example, snakes hear mainly vibrations and are not good at picking up actual sound

All reptiles can smell, but some smell better than others; for example, snakes and lizards have extra olfactory organs called Jacobson’s organs specifically for smelling.

Certain snakes (rattlesnakes and pit vipers) can detect temperature differences in their surroundings through pit organs on the sides of their head, almost like infrared vision.

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The End