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Reptiles
General Characteristics
1. Amniotic egg – shelled
2. Internal fertilization
3. Scales or plates
4. If legs – 2 pair with claws
5. Well developed lungs
6. Ectothermic – don’t generate their
own body heat
Importance of the Amnion
 Amphibians 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 Breakdown
 Kingdom –
 Animalia
 Phylum –
 Chordata
 Class –
 Reptilia
Order Testudines
Order Chelonia or Testudines
 Turtle – sea turtles
 230 species
 Webbed feet
 Soft-shelled (streamlines)
 Omnivorous – eat both plants and animals
Order Chelonia or testudines
 Terrapin – fresh water turtles
 Claws and webbed feet
 Symmetrical plates called scutes covering bony under layers
 Top shell – carapace
 Bottom shell – plastron or parapace
Order Chelonia or testudines
 Tortoise – land turtle
 Long necks, short limbs
 Appendages completely drawn into shell, if not – very aggressive
 No teeth
 Tympanic membrane (poor hearing)
 Nicitating membrane (3rd eyelid)
 Good sense of smell, good color vision
 Temperature determines sex of eggs: low temp = males
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Order Squamata
 Suborder – Sauria
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Suborder –Serpentes
some snakes are venomous
due to hemotoxins,
neurotoxins or both.
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 Mexic
 Poison is found in saliva… no fangs
 The 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 Monster
Beaded 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 feet
 FYI: 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 ears
 Evolved from lizards
 Most numerous reptile
 2,800 species (300 poisonous)
Snake Anatomy
 Long, thin – head, trunk, tail
 Scales and scutes
 Protect skin
 Prevent water loss
 Molting or ecdysis
 Skeleton
 Flexible spine of 150 vertebrae
 1 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 Movement
http://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 mouth
 Tongue picks up scent particles and inserts into Jacobson’s organ
 Tongue is forked shaped to sense the direction of the smells
Snake Sense Organs
Sight
 Cornea – permanently protected with spectacle
 Most have poor vision with exception of the arboreal (tree dwelling)
snakes
Snake Feeding
 Carnivorous
 Kills via: Poison or constriction
 Swallow food whole
 Jaw comes unhinged
 Elastic ligaments
 Glottis moves forward (so can breathe while swallowing)
 Large esophagus
 No sternum
 Strong stomach acid
Swallow Prey
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Non poisonous snakes
 Garter snake
 Black snake
 King snake
 Boa constrictor
Poisonous Snakes
 Vipers
 Rattlesnakes, copperheads, adder
 Heat sensitive pits on head (pit vipers)
 Long thin fangs – fold up when mouth is closed
Copperhead
Rattlesnake
Puff Adder
 Elapsids (cause swelling of lymph nodes)
 Cobras, coral, kraits
 Permanently erect fangs (short)
 Hydrophiidae (family) – sea snakes
 Highly poisonous – nonaggressive
 Colubridae (family, both non and poisonous) – African boomslang and twig snakes
 rear fanged
Cobra
Coral Snake
Krait
Top Ten Most Deadly Snakes
1) 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 Venom
 Neurotoxin – affect nervous system
 Hemotoxin or hemmoragin – affects red blood cells
 All contain both types, the amounts of each may
differ
 Danger is in the amount and concentration of
injected venom
 Where:
 In blood vessel… spread fast
 In muscle or fat… spread slow
Snake Reproduction
 Oviparous – lay eggs
 Oviviparous – retain
eggs in body, born alive
 Viviparous – primitive
placenta forms; receives
nourishment from
mother (rare)
Order Crocodilia
Order Crocodilian
 Carnivorous
 4 chambered heart
 Raised nostrils and eyes (so rest of body is underwater)
 Valve at back of mouth prevents water from entering lungs
when mouth is open
 Teeth in sockets (thecodont)
Eyesight in Reptiles
 Most 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 Crocodilian
 Differences 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 Crocodilian
 Both Alligators and Crocodiles are…
 Oviparous (egg-laying)
 Guard nest and care for young
 As with many turtles and some lizards – temperature of
nest determines sex of young
 Low temperature = females
Hearing & Smelling
 All 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.
The End
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