contains ~6500 species of crocodiles, turtles, snakes, and lizards, tuatara in Australia
more widespread than the amphibians, which are limited by temperature and moisture

tetrapods - a few have secondarily lost their limbs (snakes and glass lizards)
have a protective skin covered with reptilian scales of epidermal origin made from keratin - prevents water loss and slows dehydration rates
found in essentially all habitat types
claws usually present on the ends of the digits
have an amniotic egg - the developing embryo is surrounded by an amnion which contains the watery amniotic fluid
shells also present to protect the egg from dessication
all have internal fertilization accomplished by a copulatory organ

penis
hemipenis: outpocketing of the cloaca
tuatara lack a copulatory organ - mate by repressing the cloaca
oviparous, viviparous, or ovoviviparous

ectothermic - cannot control their body T physiologically; must depend on behavioral actions by moving to suitable habitats
most with three-chambered heart but crocodilians with functional four-chambered heart
lung-breathers - no gills or larval stages

Order Testudinata (Chelonia) - turtles
Order Crocodilia - crocodiles and allies
Order Rhynchocephalia - tuatara
Order Squamata - snakes and lizards

Subclass Anapsida

based on lack of a temoral opening on the side of the skull
only living order Testudinata - turtles

Subclass Diapsida

reptiles with two temporal openings
have radiated into large groups
Archosaurians: advanced lizards with tendencies toward bipedalism; led to development of thecodonts (teeth in sockets) - dinosaurs, pterosaurs, crocodilians
Lepidosaurians: primitive reptiles which developed into Rhynchocephalans and Squamates

Subclass Synapsida - gave rise to mammals

• has a shell consisting of plastron and carapace composed of bony underneath and horny epidermal scales called scutes
• vertebral column fused to the carapace except for the neck and tail
• cryptodira: “hidden-necked” turtles which retract their necks into the shell
• pleurodira: “side-necked” turtles which wrap their heads around the side of the shell
• some predaceous, some herbivorous
• all oviparous with no parental care
• some live over 100 years and weigh over 600 lbs - Galapagos tortoise
• ~240 species in the world, 47 in US

• males are smaller than females
• female plastron convex, male’s concave
• males have longer claws

• large predaceous freshwater turtles with ridged carapace joined to plastron by cartilage
• Chelydra serpentina (snapping turtle) and Macroclemys temmincki (alligator snapper)

• Graptemys kohni - Mississippi map turtle: spines sticking out at vertical scutes; stripes follow around the center of  the eye
• Terrapene carolina - three-toed box turtle: plastron and carapace not brightly colored; called “box turtles” because they can fully enclose body in shell
• T. ornata - ornate box turtle with four toes on back foot; more colorful
• Pseudemys concinna - River cooter: no red in head; yellow splits under the chin to form a “Y”
• Pseudemys scripta - red-eared slider: has red ear; older males tend to get melanistic
• Malaclemys terrapin - Diamondback terrapin: somewhat endangered because of highly prized meat

• Sternotherus carinatus - Razorback musk turtle: no coloration on carapace
• S. odoratus - Stinkpot: may be mistaken for the Mississippi mud turtle, has four barbels

• highly aquatic, long necks, no scales or scutes
• Trionyx sp. - Softshell turtles:

Represented only by Sphenodon punctatus and S. guentheri on small islands off the coast of New Zealand

primitive lizard-like reptile with two temporal openings

premaxillaries somewhat beak-like with teeth fused to the jaw and not replaced throughout life span

Represented only by Sphenodon punctatus and S. guentheri on small islands off the coast of New Zealand
primitive lizard-like reptile with two temporal openings
premaxillaries somewhat beak-like with teeth fused to the jaw and not replaced throughout life span

~6000 species
snakes have secondarily lost their limbs so the order split into two suborders

~74 species of lizards, 91 snakes in US, none in Alaska
lizards distinguished from snakes by moveable eyelids; glass lizards also distinguished from snakes by circular scale pattern (snakes elliptical) and external ear opening
smaller lizards 1st order insectivores, larger may be herbivorous; all snakes predaceous
reproduction via hemipenis - everted during copulation, one side inserted into female cloaca, sperm carried by groove called the sulcus spermaticus

the group mat be included in the Order Sauria
contain about 3000 species
all have eyelids, external ear openings in most
four legs in most
mandibles are fused anteriorly
most insectivorous, some carnivorous, some herbivorous
many species oviparous, some ovoviviparous, some may be viviparous
several species unisexual - reproduce via parthenogenesis: eggs of Cnemidophorus tessellatus (whiptail) develop without stimulus of male sperm

usually unspecialized with five clawed toes on each foot; tail may be easily separated (autotomous) - Sceloporus, Crotophytus, Anolis carolinensis

secondary loss of limbs to resemble snakes

whiptail lizards - Cnemidophorus

distinguished by expanded toe pads and large eyes for climbing and nocturnal foraging - Hemidactylus turcicus

small cylindrical bodies with short or absent legs - Scincella lateralis, Eumeces

~2125 species
no limbs
no external ear openings or eyelids
have lost the sternum, ribs extend the entire length of the vertebral column
all are carnivorous

rosy boa and rubber boa in California and Oregon

biggest about 12” long, 1/2” in diameter
eyes probably see light but can’t form image

highly venomous

characterized by a loreal pit which leads to a gland that detects heat - used to track prey

2/3 of all snakes in this form

• seize prey and swallow - unspecialized; most of this type
• constriction - captures large prey; wraps body around the prey constricting and suffocating the prey
• venom - injects a poison into the prey which kills and initiated digestion
• neurotoxic venomous snakes: chemical neuromuscular inhibitors blocking the nervous system, affects respiration where prey can’t breath - mainly in Elaphids
• hemotoxic venomous snakes: enzymes that damage tissues, breaking down tissue proteins - pit vipers

• opisthoglyphs (“behind-hollow” teeth) - one or more fangs near the maxilla with smaller teeth in front - boomslang
• proteroglyphs (“front hollow” teeth) - fangs at front of maxilla with smaller teeth behind - Elaphids, coral snakes effectively must “chew” to deliver poison
• solenoglyph teeth - hollow teeth in maxilla rotate out when mouth is opened; strike and wait for prey to die - pit vipers

largest with regard to length, up to 20 ft
21-24 species; 2 native, 1 introduced in US
• American alligator only in Walker Co.
• American crocodile
• Speckled caimen
have a distinct head, trunk, long tail; four toes of front feet, five on hind feet
have a complete secondary palate separating external and internal nares
semi-aquatic
come out on land to bask
predaceous - feed on fish, etc.

Crocodylinae - tropical crocodiles: distinguished by relatively pointed snout
Alligatorinae - alligators and caimens: snout more blunt
Gavialinae - gavial or gharial: snout beak-like

• egg layers - hard shells with rough texture
• female deposites 20-70 eggs in nest of rotting vegetation which creates heat as it decays; guarded by the female; young vocalize at hatching and female opens nest
• incubation temperature determines the sex of the developing egg
• growth rate ~1 ft per year
• ingested food not chewed - enters a gizzard that contains stones to grind the food