DIVERSITY OF EXTANT REPTILES I

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DIVERSITY OF EXTANT REPTILES I

• Turtles

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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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Amniote Egg with Shell
Reptiles, birds, mammals produce amniotic eggs.
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Groups of Reptiles

• Testudines or Chelonia (Turtles)
• Squamata (Lizards, Snakes)
• Lizards are the most numerous.
• Crocodylia (Crocodilians)

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Reptilian Skull Patterns
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Dorsal View of Turtle Skull
1.Supraoccipital  2. Opistotic  3. Quadrate  4.
Prootic  5. Postorbital  6. Squamosal  7.
Parietal  8. Postorbital  9.Frontal 10.
Prefrontal
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Side View Snapping Turtle Skull
Postorbital  2. Prefrontal  3. Premaxilla  4.
Maxilla  5. Zygomatic (jugal)  6.  Quadratojugal
  7. Quadrate  8. Squamosal 9. Supraoccipital  1
0. Parietal
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Alligator skull
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Alligator Skull
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Characteristics of the Turtles

• Outer shell encases the body.
• Anapsid skulls.
• No teeth. Tough keratinous beak present.
• Flippers present or stout club-like limbs.
• All are oviparous and lay eggs in nests or out on
  the ground.
  
• Often an elaborate courtship.

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Turtle Skeleton
The turtle body is encased in a shell made up of
a series of bony plates covered with a horny shie
ld. The vertebrae and ribs are fused to the
inside of this shell, which gives it additional
support and strength. It is impossible for turtl
es or tortoises to crawl out of their shells.
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Turtle Neck Retraction
Side neck turtles
Head pulled in
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