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