Class Reptilia

An introductory presentation for my high school Zoology Course that examines the Class Reptilia.

2. Phylum
Chordata

3. Class Reptilia
Includes turtles, lizards,
snakes, crocs, alligators,
caimans, tuatara
Tetrapods
Shelled, amniote egg
(leathery)
Inhabit every continent
except Antarctica
Ectotherms
On Earth for 300 MY

4. More Reptile Characteristics:
Many are egg-bearing
Some bear live young
Parental care
Lungs
Rows of identical teeth
Dry,scaly, impermeable
skin (keratin)
Mostly carnivorous
(insectivorous)
Claws or digits
(if present)

5. Reptile babies. . .
Eggs
Calcified shell
Leathery shell
Larval forms?

7. Order Squamata
(from L. ~ squamatus: “scaly”)
Snakes & lizards
Comprises about 96% of reptile species.
Snakes likely evolved from burrowing lizards
Very dry, scaly skin, periodically shed outer epidermis
Only vertebrates with hemipenes
Only reptile group with oviparous, viviparous and ovoviviparous
species

13. Order Chelonia
Turtles & tortoises
What is the difference?
Tortoises: land ~ Turtles: both
Shell composed of horn-like scales
Top shell: CARAPACE
Bottom shell: PLASTRON
Only the shoulders & hips move

21. Order Crocodilia
(from Greek: “krokodeilos” meaning pebble worm)
Crocodilians, Alligators, Caimans & the
Ghavial
21 species total
Crocs have a narrower face & pointed jaw
Most closely-related to dinosaurs
4 heart chambers
Single croc can go through 3,000 teeth in its
lifetime

25. Only one species of gavial (or gharial): Gavialis gangeticus

26. Order Rhynchocephalia
(from Maori for “spiny crest”)
The Tuatara
Only one genus: Sphenodon
Inhabit a few small islands of New Zealand
Disappeared from most of their original range

27. =>
Th e Tu a ta ra
Only one genus: Sphenodon
Recently split into two species; Sphenodon punctatus & Sphenodon guntheri
Inhabit a few small islands of New Zealand
Disappeared from most of their original range
Long lived: 60 to 100 years or more
Pineal eye in juveniles- becomes covered over in adults
Teeth are solid projections of the jawbone
Determination of gender by temperature
warmer: males - cooler: females
Performs best at temps around 12-17C
Most reptiles: 25-38C
Adults live in underground burrows and are nocturnal. They also are known to eat
their offspring. Therefore, juveniles live in the open for about 15 years to avoid
predation. They do not reach full size until 25-35 years!
Estimates of their remaining numbers vary largely, from 50,000 to 100,000 remaining
in the wild. (Cassey and Ussher 1999)

28. Four Legs and A Third Eye?
It's pretty common knowledge that vertebrate animals have two eyes,
but this was not always the case. Our earliest fish-like ancestors,
evolved with a third hole in their skulls and an eye that connected
directly to the brain called the pineal eye. It appears that this
adaptation became converted over time to a small organ associated
with the control of hormone production — the pineal body or gland. But
in tadpoles, other amphibians, and some of the lizards, among them
the Tuatara, a living relic lizard of the Sphenodont group, a third
centrally located eye has remained although the function is not fully
understood. It is sensitive to changes in light and dark, but it does not
form images, having only a rudimentary retina and lens. It is visible as
an opalescent gray spot on the top of the animal's head. Also, some
snakes have an "extra" pair of "eyes" (more correctly, sensory organs)
located on the forehead that can detect infrared radiation. They can
"see" the heat of a mouse from a meter away, even in conditions
where our eyes would see only pitch dark.