Diapsids

Kingdom: AnimaliaPhylum: Chordata

Subphylum:VertebrataClass: Reptilia

Subclass:AnapsidaSubclass:DiapsidaSubclass: Synapsida

What are diapsids?

It’s a subclass of class reptilia

It includes all living reptiles Turtles are excepted

It also includes reptiles that ruled the land, air and sea during the Mesozoic era

General characteristics

presence of two openings on each side of the skull

 the upper and lower temporal openings

General Characteristics

allows for the attachment of larger, stronger jaw muscles, and enables the jaw to open more widely

long slender feet with overlap in the bases of the wrist and toe bones

relatively long lower arm bone (the radius) compared to the upper arm bone (humerus).

Sample Organisms

Crotaphytus Dimetrodon

Diapsids

Lepidosauromorpha

Lepidiosauria Plesiosauria Ichtyosauria

Archosauromorpha

Crocodilia PterosauriaSaurischian Dinosaurs

Ornithischian Dinosaurs

Lepidosuria

Lepidosauria has 2 extant groups:

◦Rhynchocephalia

◦Squamata

Rhynchocephalia

Primitive lizard-like reptilesThey have quite different scales, teeth, and

internal morphology than modern lizards.Retained the Diaspid skulls from their

ancestorsAcrodont dentition (teeth fused to

jawbones)The only surviving Rhynchocephalian is

Sphenodon

Sphenodon

Feeds on small vertebrates Attains a length of 0.75m (2.5ft) Sexually mature @ 20 yrs. Old Life span may exceed 60 years The upper surface of the body is

covered with small granular scales and the lower surface is covered with transverse rows of large squarish scales.

Operate at very low body temperatures (between 6 and 16 C) Acrodont dentition

Squamata

Composed of lizards , snakes and amphisbaenians

2 Characteristics that unite squamates:

Periodic shedding of skin

◦ snakes shed their skin in one piece◦ Lizards and amphisbaenians shed their skin in patches

uniquely jointed skulls and jaws

◦ both strong and flexible◦ extraordinary jaw mobility of squamates enables them to open

their mouths very wide◦ consume large prey

Other Characteristics

Well developed appendicular musclesSuitably constructed skeletonRun agilely on their hind limbsSome are broad jumpers

Suction discs on toes◦Adhere to smooth vertical surfaces◦Geckoes

Glide through air◦Due to rib supported extensions of the lateral

body wall◦Draco, the flying dragon

Few lizards are either limbless or have only vestiges of limbs

Some lizards are blind

Spectacles-transparent eyelids

Nicitating membrane – 3rd eyelid

◦Protection and moisture for the eye w/o blocking vision

Snakes evolved from lizards◦Lost limbs◦Acquired other modes of locomotion

Lateral progression- lashing of body back and forth causing lateral waves that force longitudinal motion. To put it another way: They go forward by moving sideways.

◦Large ventral scales or scutes◦Viviparous

Giving birth to living offspring that develop within the mother's body.

Amphisbaenians are subterranean lizards◦Limbless◦Annulated bodies similar to apodans◦Drum and eyes are covered with opaque skin

much greater degree of bone in the skull Internally, their right lung is reduced in

size to fit their narrow bodies distinctive single median tooth in the

upper jaw. carnivorousThey move using an accordion-like

motion