This document provides a classification of reptiles based on their anatomical features. It discusses the five subclasses of reptiles: Anapsida, Euryapsida, Parapsida, Synapsida, and Diapsida. Within Diapsida are two superorders - Lepidosauria containing lizards and snakes, and Archosauria containing crocodilians. Key characteristics are described for each order, including turtles within Anapsida, lizards and snakes within Lepidosauria, and crocodilians. Temporal bone structure is an important distinguishing feature between subclasses.

1. Class:Reptilia-Classification
Turtles, Tortoises, Tuataras,
Crocodilians, Lizards, and Snakes
B.Ashok Kumar
Assistant Professor
KRK Govt. Degree College
Addanki-523201
9652929696
ashokkumarzoology@gmail.com

2. Classification
• Kingdom Animalia
• Phylum Chordata
– Subphylum Vertebrata
• Class Reptilia
There are more than 7,000 living and several
extinct species
• Five sub classes- Temporal fossae
– Anapsida
– Euryapsida
– Parapsida
– Synapsida and
– Diapsida

5. Sub class: Anapsida
• Temporal fossae absent
• Temporal region is completely bony
• Two orders:
– 1. Cotylosauria
– 2. Chelonia

6. Order:Cotylosauria
• Extinct
• Stem reptiles
• Pelvic girdle plate like
• Resembles Labyrinthodont Amphibians
• Eg: Seymouria

7. Order: Chelonia/Testudinata
• Turtles , Terrapins and Tortoises
– Body- short, broad
– Limbs paddle like with claws
– Shell consists of fused boney plates
• Carapace (Dorsal, top)
• Plastron (Ventral, lower) Head &Tail -retracted into the shell
– Anapsid skull
– Jaws- edentate & covered by horny sheath
– Most species ribs and spine fused to inner surface of
carapace
– Pelvic and Pectoral girdles lie within the ribs
– Sharp beak instead of teeth

8. • Ductus Botalii- connects
systemic and pulmonary
arches
• Males- single penis,
longitudinal cloacal
aperture
• Variety of habitats, longest
life span
• Eg:Testudo, Chelonian
mydas, Dermochelys,
Trionyx
Order: Chelonia

9. • Shell and limbs reflect habitat

10. Sub class2: Euryapsida
Extinct
Skull with a single dorso-lateral temporal
opening on either side.
These openings are bounded below by
postorbital and squamosal bones.
They lived during Triassic period.

11. Sub class3: Parapsida
• Extinct
• Skull-parapsid
• Skull with a single dorso-lateral temporal opening
on either side.
• These openings are bounded below by the supra
temporal and post frontal bones.
• They lived during Mesozoic to cretaceous period.
– Mesosauria- Extinct Eg: Mesosaurus
– Ichthyosauria- Extinct Eg: Ichthyosaurus
– Proterosauria- Extinct Eg: Araoscelis
– Sauropterygia- Extinct Eg: Cyamodus, Kronosaurus

12. Mesosaurus

13. Sub-class 4:SYNAPSIDA
• Extinct
• Synapsid skull
• Skull with a single lateral temporal opening on
either side.
• These openings are bounded above by the
postorbital and squamosal bones.
• They lived during Carboniferous to Permian
period.
• Eg: Dimetradon, Cyanognathus, Tritylodon

14. Sub class4: Diapsida
• Skull with two temporal openings on either
side separated by the bar of postorbital and
squamosal bones.
• This sub- class includes 2 super orders.
• Super order 1. Lepidosauria(Scaly lizards)
• Super order 2. Archosauria(Ruling reptiles)

15. Super order1: Lepidosauria
• Two temporal vacuities- diapsid skull

16. Order1: Rhynchocephalia
• Ancient order inhabit few
small islands of New Zealand
• Body small, elongated, lizard
–like
• Limbs pentadactylous,
clawed and burrowing.
• Skin covered by granular
scales and a mid-dorsal row
of spines.
• Spiny crest that runs down
the animal’s back

17. Order1: Rhynchocephalia
• Vertebrae amphicoelous or biconcave.
• Numerous abdominal ribs present.
• Teeth acrodont.
• Perietal foramen-non functional median eye
• Cloacal aperture transverse/
• No copulatory organs in male.
• Tolerate cool temp, burrow during day and hunt at
night
• Example - Sphenodon punctatum or tuatara lizard

18. Order2: Squamata
• Lizards and Snakes

19. Order2: Squamata
• Body small to medium, elongated and advanced.
• Limbs, clawed, absent in snakes and few lizards.
• Body covered by horny epidermal scales, shields
and spines.
• Vertebrae procoelous.
• Ribs single headed.
• Teeth acrodent or pleurodent.
• Upper jaw is loosely joined to the skull
• Paired Jacobson’s organ

20. Order2: Squamata
• Cloacal aperture is transverse
• Male with eversible double copulatory organs
(hemi-penes)
• This order includes two sub-orders.
• Sub order – 1 Lacertilia
• Sub order – 2 Ophidia

22. Suborder – 1 – Lacertilia
• Commonly known as lizards.
• Limbs and girdles usually well-developed.
• Eyelids movable. Nictitating membranes present.
• Ear openings and tympanum present.
• Maxillae, palatines ad pterygoids fixed.
• Mouth non-expansible.
• Sternum, episternum and urinary bladder usually
present.
• Tongue rarely notched or extensile.
• Eg:Hemidactylus, Calotes, Uromastix Varanus,

23. Lizards
• Only 2 species venomous
– Gila Monster
– Bearded Lizard
• Autotomy

25. Sub- order – 2 Ophidia
• Limbs and griddles absent, vestigial hind limbs and
pelvic girdle in boa, python etc.
• Eye lids fixed. Nictitating membranes absent.
• Auditory openings and tympanum lost.
• Maxillae, palatines and pterygoids movable helping
in biting mechanism.
• Mouth can be widely separated.
• Sternum, episternum and urinary bladder usually
absent.
• Tongue slender, bifid and extensible.
• Ex - Python, Boa, Naja, Bungarus, Vipera etc.

28. Order Crocodilia
• Crocodiles, Alligators, Caimans, Gavial

29. Order3: Crocodilia
• Most closely related to dinosaurs
• Heavy bodied, mostly aquatic
• Carnivorous
• Double headed ribs
• Diaphragm

30. Order 3 – Crocodilia (Loricata)
• Body large-sized, carnivorous and aquatic reptiles.
• Limbs short but powerful, clawed and webbed.
• Tail long, strong & laterally compressed.
• Body surface-horny epidermal scales/bony plates/
scutes.
• Teeth thecodont, numerous.
• Abdominal ribs present (gastralia).
• Cloacal aperture-longitudinal
• Heart completely 4 chambered.
• Male with a median, erectile, grooved penis.