Phylum Chordata
Class Reptilia:
-First truly terresterial vertebrates.
-amnion: enclosed a fluid-filled cavity "the Pond" embryo floats.
-allantois: serves as a respiratory & store nitrogenous wastes
-chorion: O2 and CO2 freely pass
-Finally the Shell
-turtle, lizards, snakes, crocodilians, tuataras are survivors of radiation that happened
during mesozoa period.
-Reptiles & birds came from same ancestors.
Characteristics:
1.exoskeleton, horny epidermal scales
2. few glands in integument
3.usually pair of limbs with five toes
4.ossified skeleton, no sternum in snake
5.skull has one occipital condyle
6.Lungs and no gills
7.Cloaca can be used for respiration by some.
8.three chambered heart, crocodilians have four
9.Uric acid is nitrogenous waste
10.Cranial nerves 12 pairs
11.sexes separate, fertilization internal
12.Eggs covered with calcareous or leathery shells
13.no aquatic larval stages
What makes Reptiles different from Amphibians:
1.tough skin
A.keratin in scales
B.not homologous to fish
C.Snakes shed their skins, turtles add a new layer to the old one.
2.the shelled eggs with amniotic fluid.
3.jaws are for crushing, gripping, fishes and amphibians jaw for quick closure. Jaw
muscles in reptiles bigger.
4.copulatory organ for internal fertilization
5.more efficient circulatory system and higher blood pressure
6.lungs better developed than those of amphibians.
7.more efficiently designed limbs, for traveling on land
8.more complex nervous system
Anapsid reptiles:
Subclass Anapsida:
-Skull has no temporal opening, behind the orbits. only turtles are representative
of this group
order Testudines (chelonia): Turtules
-dorsal carapase and ventral plastron (breastplate)
-shell fused to thoracic vertebrae and ribs
A.outer layerkeratin
B.inner layer bone
-jaw lack teeth but have horny plates for gripping
-they have middle and inner ear but sound perception is poor
-good vision
-oviparous
-low metabolism so they live long
-Eastern snapping turtule have small shell
-Snappers are carnivorous
-Snappers are aquatic and come to shore to lay eggs.
Diaspid reptiles
-skull has two temporal opening
order squamata: Lizards, snakes, and worm lizards
-most recent group 95% of all reptiles belong to this group
-Kinetic skull
-skull of snakes is even more kinetic than of Lizard
suborder Sauria: lizards
-geckos, small, agile, nocturnal, adhesive toe
-iguanas, brightly colored
-new world's lizards, marine iguana
-Skinks, elongated bodies, reduced limbs
-glass lizards, no limbs at all
-lizards eyes are movable and snake eyes are covered with a cap
-Lizards have cones and rods
-geckos have rods
-lizards have external ear snakes don't
-lizards in hot region
-They have semisolid urine
-made up of crystalline uric acid.
-Gila monster store fat in their tail.
suborder Amphisbaenia: worm lizards
-burrowing organism, means "double walk"
-eyes & ears hide under skin
-
one species found in Florida "graveyard snake"
suborder Serpentes: snakes
-all limbless
lack pectoral and pelvic girdles
-Kinetic skull
-can eat preys several times of their size
-most poor vision, except tree-living ones
-have internal ear, no external and middle ear
-so they can hear low frequency pitch
-sensitive to vibrations carried in the ground
-chemical senses lead them to hunt
-Jacobson's organs
-skin is covered with scales that overlap each other
-skin is not elastic
-after a meal folds of skin unfold
-family viperidae, pit vipers
-rattlesnakes, copperhead
-all vipers have a pair of teeth on maxilla as a fang
-sensetive to heat and vibration
-two types of venoms:
1. neurotoxic
2. hemorrhagin
-toxicity of venom is meared by a method called LD50, median lethal dose
-most snakes are oviparous
order sphenodenta: the tuatara
-only survivor of sphenodontid from mesozoic era
-
found only in New Zealand
order crocodilia: crocodiles, and alligators
-All have elongate robust, well reinforced skull, massive jaws,
-teeth with indentation
-secondary palate allow breathing when mouth is filled with food or water or both
-Alligators are less aggressive
-leave nests unguarded
-alligators unusual that can make noise
-both are oviparous
-Incubation temperature determine the sex of animal
turtlesalligator & crocodiles
low temp.malelow temp.female
high temp.femalehigh temp. male
-temperature - dependent reptiles lack sex chromosomes