Reptiles!!!
Classification
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Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Reptilia
– Orders:
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Crocodilia
Sphenodontia
Squamata
Testudines
Characteristics
• Ectothermic(Cold-blooded)
• Regulate body temperature by seeking or
avoiding sun.
• Air Breathing
• Tetrapods
• Scales instead of feathers or hair
• Three and a half chambered hearts
• Most lay eggs
• Amniotes!
Evolutionary Milestone
• The Amniote Egg
– Adapted for land.
– Allows for full
development inside
safety of egg.
Reptile History
• First reptiles appeared around 380 million years
ago, during the Pennsylvanian time period, when
the climate was warm and humid, and
amphibians dominated.
• Many different reptile species appeared during
the Triassic, which had a drier, cooler climate.
• Today, 6,500 species of reptile walk and slither
on the Earth, and reside on every continent,
except Antarctica.
The Four Reptilian Orders
Testudines
Squamata
Crocodilia
Sphenodontia
Sphenodontia
• 2 species of Tuatara
living in New Zealand; all
others went extinct 60
mya.
• Has not changed in 225
million years
• Living fossil!
• They have a 3rd “eye”,
have no external ear
openings, and males lack
a penis.
Crocodilia
• Appeared 85 mya
• Large reptiles with
elongated head
• Alligators, Crocodiles,
Caimans, and Gharials
• 4 Chambered Heart
• Teeth in bony socket
• Closest living relative to
birds.
Testudines
• Turtles and Tortoises
• Bodies with two-piece
bony shell
– Carapace: dorsal; arose
from ribs
– Plastron: ventral
• Appeared in fossil
record 220 mya
Squamata
• Lizards and snakes
• 5640 species!
• Tough epidermal scales
made of keratin
• Possess moveable
quadrate bone.
• Most variable order in
size