REPTILE CHARACTERISTICS: The Snakes

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REPTILE CHARACTERISTICSThe Snakes
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Extant Reptiles

• 15,800 species
• Testudines (Chelonia) 260
• Aves 8,700
• Squamates 6,850
• Crocodilians 2
• Tuatara 2

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Characterisitcs of Reptiles

• Scales with keratin help prevent water loss.
• 3-chambered heart except crocodilians.
• Almost all have lungs.
• Internal fertilization.
• Most reptiles lay shelled amniotic eggs on land.
• Some have young born alive (viviparous) with
  extraembryonic membranes forming placenta.
• Ectothermic and regulate body temperature.

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Characteristics of Snakes

• Diapsid skull.
• Replacement of teeth occurs through life.
• Reduction of bones in limbs.
• Pair of copulatory organs, hemipenes.
• Oviparity and viviparity occur.
• Shedding of epidermis occurs regularly.
• Reduced left lung.
• Transparent spectacle covers the eye.
• 120 400 precloacal vertebrae.

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Reptilian Skull Patterns
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Diapsid Skull
Python Skull
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Snake Teeth

• Teeth are superficially attached
• Acrodont if located on top of jaw
• Pleurodont if attached to outside edge of jaw
• Or firmly attached in sockets
• Thecodont
• Teeth are replaced
• because of wear and
• tear.

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Limbs of Snakes

• Not present ordinarily
• but in primitive
• snakes (Boidae), a
• rudimentary pelvic
• girdle is represented
• by cloacal spurs.

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Copulatory Organs Hemipenes
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Oviparous
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Emergence of young snakes
Viviparous
Oviparous
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Shedding of Skin Ecdysis
Shedding cycle
After shedding
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Spectacle of Eye
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Viperidae

• Vipers may be terrestrial or arboreal.
• Habitats range from rain forests to deserts and
  high mountains.
• Oviparous or viviparous.
• Representatives include rattlesnakes, eyelash
  vipers, bushmasters, copperheads,
  fer-de-lances.
• All have fangs and are venomous.

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A Pit Viper Heat detecting pit located between
eye and nostril.
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Crotalus adamanteusEastern Diamondback
Rattlesnake
Crotalus
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Eastern Diamondback Rattlesnake
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Crotalus horridusTimber Rattlesnake (Canebreak)
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Eyelash ViperCentral, South America
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Agkistrodon piscivoorusCotton Mouth
Broad dark stripe present behind eye. Black
crossbands on lighter background.
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Agkistrodon contortrixCopperhead