Diapsids are a subclass of reptiles that first appeared during the Permian period. They are distinguished by having two openings on each side of the skull. Modern diapsids include reptiles like lizards, snakes, crocodilians, birds, and their extinct relatives. Diapsids ruled land, air, and sea during the Mesozoic era and are characterized by having two temporal fenestrae in each side of the skull which allowed for stronger jaw muscles.

1. Diapsids

2. Kingdom: Animalia
Phylum: Chordata
Subphylum:Vertebrata
Class: Reptilia
Subclass:Anapsida
Subclass:Diapsida
Subclass: Synapsida

3.  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
What are diapsids?

4. presence of two openings on each side
of the skull
 the upper and lower temporal openings
General characteristics

5.  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
General Characteristics

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

7. Crotaphytus Dimetrodon
Sample Organisms

8. Diapsids
Lepidosauromorpha Archosauromorpha
Lepidiosauria Saurischian Ornithischian
Plesiosauria Ichtyosauria Crocodilia Pterosauria Dinosaurs Dinosaurs

9. Lepidosuria

10.  Lepidosauria has 2 extant groups:
◦ Rhynchocephalia
◦ Squamata

11.  Primitive lizard-like reptiles
 They have quite different
scales, teeth, and internal morphology
than modern lizards.
 Retained the Diaspid skulls from their
ancestors
 Acrodont dentition (teeth fused to
jawbones)
 The only surviving Rhynchocephalian is
Sphenodon
Rhynchocephalia

12. 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

13.  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
Squamata

14.  Well developed appendicular muscles
 Suitably constructed skeleton
 Run agilely on their hind limbs
 Some are broad jumpers
 Suction discs on toes
◦ Adhere to smooth vertical surfaces
◦ Geckoes
Other Characteristics

15.  Glide through air
◦ Due to rib supported extensions of the lateral
body wall
◦ Draco, the flying dragon

16.  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

17.  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.

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

20.  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.
 carnivorous
 They move using an accordion-like
motion