KINGDOM ANIMALIA Phylum Chordata Subphylum Vertebrata Class Reptilia
Dec 30, 2015
KINGDOM ANIMALIAPhylum Chordata
Subphylum VertebrataClass Reptilia
Vertebrate Classes
History
Reptiles are the evolutionary base for the rest of the tetrapods.Early divergence
of mammals from reptilian ancestor.Early reptiles
arose from amphibian ancestor and were small, lizard-like insectivores.
Common FeaturesPositioning of legs
more directly under animal (more support).Paired limbs with
five toes. – Adapted for running,
climbing, swimming.– Absent in snakes.
Common FeaturesBody covered with
horny epidermal scales made from protein keratin. – Scales serve to reduce
water loss and provide protection.
– Reptiles molt as they grow.
Jaws adapted to biting/tearing.
Common featuresRespiration through
internally protected and moistened (a moist cloacal surface in some turtles).Most reptiles have a 3-
chambered heart with a partially divided ventricle. – No mixing of blood from
lungs with deoxygenated blood.
– Crocodiles have 4 chambers and a unique feature: cog teeth.
Story About the Crocodile Heart
Common featuresExcretory waste = uric
acid (doesn’t waste water)Brain = first cerebral
cortex (capable of reasoning, planning, perception)
Still ectothermic– Must live in favorable
conditions or hibernate.– Being ectothermic enables an
organism to survive on much less food than an endothermic organism.
ReproductionInternal fertilization: gametes not subject
to desiccation. Amniote egg = significant evolutionary
breakthrough.– Egg covered by tough, water-resistant, leathery
or calcerous shell.– Extraembryonic membranes compartmentalize
the interior for several functions.
Amniote Egg
Amniote EggChorion = hard covering permeable
to respiratory gases but not water.
Allantois = functions in gas exchange and a storage reservoir for metabolic waste.
Amnion = fluid-filled sac acts as cushion for embryo and prevents desiccation.
Yolk sac = food for embryo; eliminates need for larval stage.
Reptile SkullsExcept for turtles, all reptiles
have two temporal openings in the skull.
These openings have allowed for attachment and expansion of the jaw muscles.
Subclass AnapsidaOrder Testudines
260 species of turtles/tortoisesOldest group of reptiles (225
mya)Protective body shell
– Encases vital organs– Provdes some protection to
head/limbs– Composed of bony plates covered by
horny epidermal scales– 2 parts: upper carapace, lower
plastronPrimitve features:
– Loss of body-wall muscles– Ribs/trunk vertebrae fused to
carapace– Lack teeth/horny beak grab and tear
food
Subclass AnapsidaOrder Testudines
All lay eggs on land.
Third eyelid = nictitating membrane.
Longest living vertebrates (100+years in wild)!
Subclass DiapsidaSuperorder Lepidosauria
– Order Squamata• 4675+ species of lizard• 2700+ species of snakes• 140 species of amphisbaenians
– Limbless, burrowing animals– Vestigial eyes under skin
– Order Rhynchocephalia• 2 species of Tuatara• Solitary, nocturnal, burrowing
animal
Most successful/diversified of living reptiles.
Occur in most habitats of world.Snakes:
– Elongated derivative of lizard (increased vertebrae, not lengthening of segments)
– Lack limbs, eyelids, ear openings– Jaw bones are loosely united to allow
swallowing of large prey– Throat and windpipe are at separate ends of
mouth to allow breathing while eating– Can be venomous (hemotoxin/neurotoxin)– Tongue to smell, some have heat pits to
sense body heatLizards:
– Legs, eyelids, ear openings– Halves of lower jaw united
Order Squamata
Superorder ArchosauriaIncludes extinct
dinosaurs/pterosaurs and birds
23 species of crocodiles, alligators, & caimans
Largest of the living reptiles
Amphibious carnivoresLive in tropics/subtropicsLizard-like body with short
legs, clawed/webbed toes, massive tail
Flat head with nostrils at tip
Powerful jawsDorsal side armored with
dermal plates