Reptiles
Characteristics of Reptiles
1. Strong, bony skeletons and feet with
claws
2. Ectothermic (cold-blooded)
3. Dry scaley skin
4. Amniotic eggs
5. Respiration with lungs
6. Ventricle partially divided
7. Internal fertilization
Order Rhynchocephalia
Tuatara - Only found in New
Zealand, they have no
external ears and a 3rd eye
Turtles and Tortoises
• Turtles and tortoises differ from other reptiles in
that their bodies are encased within a hard, bony,
protective shell. Many of them can pull their head
and legs into the shell for effective protection
from predators.
• Today’s turtles and tortoises differ little from the
earliest known turtle fossils, which are more than
200 million years old.
Still under debate…
• Turtles are the last big living vertebrate group to be placed firmly on the tree
of life
• Three fields in particular — paleontology, developmental biology and
microbiology/genomics — disagree about how, and from what, turtles may
have evolved.
• Some scientists argue turtles are more closely related to snakes and lizards
other feel they are birds and crocodiles.
• Turtles and tortoises lack teeth but have
jaws covered by sharp plates.
• Many are herbivores, but some, such as
the snapping turtle, are aggressive
carnivores.
Turtles vs. Tortoises
• There are 260 species of turtles, but
only seven species of sea turtles in the
world, 5 of which are found in the south
east.
• Most turtles live in the water and
tortoises on land.
• While most tortoises have a domeshaped shell, water-dwelling turtles
have a streamlined, disk-shaped shell
that permits rapid maneuvering in water.
The top of a turtle's shell is the carapace, the
bottom is the plastron
Is this a turtle or a tortoise?
Order Squamata
Snakes & Lizards
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Have legs (vestigial on snakes)
clawed toes
external ears
moveable eyelids
Komodo Dragon
• When hunting, Komodo dragons rely on
camouflage and patience, lying in wait for
passing prey.
• When a victim ambles by, the dragon
springs, using its powerful legs, sharp claws
and serrated, shark-like teeth to eviscerate
its prey.
• Their saliva contains over 50 strains of
bacteria, and within 24 hours, the stricken
creature usually dies of blood poisoning.
• Dragons calmly follow an escapee for miles
as the bacteria takes effect, using their keen
sense of smell to hone in on the corpse.
• A dragon can eat a whopping 80 percent of
its body weight in a single feeding.
Snakes
All snakes swallow their prey whole.
Snakes can be constrictors or venomous to kill prey.
One day, a baby snake went over to his dad and said
“Dad, are we the kind of snakes that are venomous, or
are we the constricting kind?”. The dad replied “Why
do you ask, son?”
The baby snake said: “Because I bit my lip.”
Myth Busted!
• Snake jaws DO NOT DETATCH
• The two lower jaws move
independently of one another
• The quadrate bone is not rigidly
attached to the skull, but articulates with
the skull at one end and is therefore
freely moving.
• The elasticity of the ligament between
the mandibles allows for further
stretching
Lost snake species rediscovered!
Family Crocodilia
• 4 chambered heart
• Poikilotherm (cold blooded)
• Live in groups known as “pods”
Alligator or
Crocodile?
Crocodilians
• There are 23 recognized species of Crocodilians broken
down into: (will be 26/27 soon)
– 2 Species of Alligators
– 14 Species of Crocodiles
– 6 Caiman
– 1 Gharial
• The only place in the world where Crocodiles and
Alligators co-exist in the wild is in Southern Florida
What’s the difference?
• The rounded or
shovel shape of the
alligator's head
versus the triangular
tapering shape of the
crocodile is the most
visual distinguishing
features.
• Crocodiles usually
have an “under-bite”
allowing teeth to be
seen even with its
mouth closed.
Dermal
Pressure
Receptors
• Both crocodiles and alligators have small, sensory pits
dotted around the upper and lower jaws.
• These are capable of detecting small pressure
changes in water, and assist in locating and capturing
prey.
• Crocodiles have similar organs covering virtually every
scale on their body, but alligators and caimans only
have those around the jaws
• Crocodiles and gharials also have functioning
modified salivary glands on their tongue. While
alligators and caimans also have these
structures they appear to have lost the ability to
use them for excreting significant amounts of
salt. This makes crocodiles more tolerant to life
in saline water.
• It suggests that crocodiles have a more recent
marine ancestry: the ability to migrate across
wide marine bodies, and even live there for
extended periods. would certainly explain their
current wide distribution across different
continents. Alligators and caimans have lost
much of this osmotic ability to secrete excess
salt through the tongue glands, and can only
tolerate it for short periods of time.
Modern Dinosaurs
• Crocodilians date back over 230 million years
• Crocodilians have been virtually unchanged for the last 65
million years
SuperCroc likely measured about 40 feet (12
meters) long and weighed as much as ten tons. Its
jaws alone measured 6 feet (1.8 meters)—as long
as a tall human
Sarcosuchus imperator,
or “flesh crocodile
emperor,” lived roughly
110 million years ago,
when rivers coursed
over what is now subSaharan Africa.
Sarcosuchus prowled
the rivers’ banks,
crushing fish — and
other creatures—in its
massive jaws.
Fossilized skull of Dunkleosteus terrelli, or "terrible fish," a 33foot (10-meter) behemoth that lived 400 million years ago.
Scientists used the monster's skull to recreate the
musculature of the fish's head and found that its colossal jaws
delivered a bite with a remarkable 1,100 pounds (540
kilograms) of force.
Bite Force
• In the American Alligator (Alligator
mississippiensis) has been measured
at up to 2,125 P.S.I. and is known to
be the 2nd greatest in the animal
kingdom
• In the Salt Water Crocodile
(Crocodylus porosus) has been
measured at up to 3,000 P.S.I. and is
thought to be the greatest in the
animal kingdom
• Compare that with a lion at 940
pounds.
Bite Force Studies
Teeth
• Crocodilians have between 70 and 80
teeth at any given time
• Teeth are last and replaced continuously
with each individual tooth being replaced
at a rate of approximately once annually
(That’s approximately 2,000 teeth in a
lifetime!)
• Crocodile vs. Alligator teeth
• Nutritional Importance
“Egg Tooth”
• A modified piece of skin which forms
during development of the embryo
(Not a true tooth made from bone.)
• When the time comes to emerge, the
crocodile normally rubs the tip of its
snout up and down against the inner
membrane of the egg. The sharp egg
tooth slices apart the inner
membrane, and the hatchling can
then push its nose forwards forcefully
to crack the outer membrane.
This event, where the
baby crocodilian pierces
the eggshell membrane
and sticks its snout out
into the air, is called
pipping
The Amniote Egg
Contains a water and food supply for the
embryo and can be laid on land.
Must be
fertilized
internally,
has a shell
Snakes Hatching
Parts of the Amniote Egg
Amnion = watery environment
Yolk = food for embryo
Allantois = stores waste
Chorion = membrane, gas exchange
Albumen = egg white, cushion
Juvenile crying
http://www.flmnh.ufl.edu/cnhc/images/!amis9b.wav
The eye-shine of an alligator (and
other nocturnal vertebrates) is
caused by a layer of cells called the
tapetum lucidum (a Latin phrase
meaning "bright carpet").
This structure reflects light back into
these cells to increase the amount of
light detected and improve the
animal's vision in low light conditions.