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Lizards and snakes

DBS 402B.2Presidency University, 2016

Amniotes

Reptilia•

First true terrestrial chordate

•

Limbs ending in claw•

Skin is covered with non-glandular scales

•

Proceolous

vertebrae •

Thecodont

teeth

•

Nucleated, biconvex RBC•

Metanephric

kidneys

Reptiles •

Class Reptilia

[Dry skin with epidermal scales; skull with one point of articulation with the vertebral column (occipital condyle); respiration via lungs; metanephric

kidneys; internal fertilization; amniotic eggs]–

Order Testudines

or Chelonia

[Teeth absent in adults and replaced by a horny beak; short, broad body; shell consisting of a dorsal carapace and ventral plastron.] Turtles.

–

Order Rhynchocephalia

[Contains very primitive; lizardlike

reptiles; well-developed parietal eye. A single species, Sphenodon

punctatus, survives in New Zealand.] Tuataras.

–

Order Squamata

[Recognized by specific characteristics of the skull and jaws (temporal arch reduced or absent and quadrate movable or secondarily fixed); the most successful and diverse group of living reptiles.] Snakes, lizards, worm lizards.

–

Order Crocodilia

[Elongate, muscular, and laterally compressed; tongue not protrusible; complete ventricular septum.] Crocodiles, alligators, Chorion

caimans, gavials.

Miller Harley

Squamata•

Skull with superior temporal fossa

•

The maxilla, palatine and pterygoid

are immovable (in lizards but movable in snakes) but quadrate is movable (more in snakes than lizards)

•

Teeth is either acrodont

or pleurodont•

Procoelous

vertebrae

The skull

The skull development

Skull, musculature in jaw movement

Cranial kinesis in squamates

The differences

Lizards

Snakes

Lizard skull

Snake skull

The vertebrae

The difference

Lizards don’t have them

Lizard scale

Snake scales

Sum up?

Continued

Books

Kardong, Miller Harley, Linzey, Rastogy