Evolution of reptiles

1. Seminartopic:
EVOLUTION OF REPTILES THROUGHAGES

2. Seminar Content
• Introduction - EVOLUTION
• Representing vertebrate evolution
• Labyrinthodonts
• Amniotic egg
• Classification of reptiles
• Skull
• Vertebral Column
• Limbs and Skin
• Mass extinction
• Conclusion
• References

3. INTRODUCTION
•Evolution is the change in the inherited characteristics of
biological populations over successive generations.
• Evolutionary processes give rise to diversity at every level
of biological organization, including species, individual
organisms and molecules such as DNA and proteins
• A Reptile is any amniote (tetra pod that can lay eggs on
land) that is neither a mammal nor a bird.
• Unlike mammals, birds, and certain extinct reptiles, living
reptiles have Scales or scutes (rather than fur or feathers)
and are cold blooded.

4. BODY
FINSFINS
BODY
BODY
BODY
EVOLVED VERTEBRATES-
Terapods to Bipods body
lifted from the ground
with two legs
REPTILES-TETRAPOD –Body
lifted from the ground
AMPHIBIANS-
TETRAPOD –Both Limbs
(Fore & Hind) and body
touches the ground
(Parallel to ground)
PISCES – Body
adopted to live in
water with fins
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REPRESENTING VERTEBRATE EVOLUTION

5. LABYRINTHODONTS
• The reptiles were derived from the amphibians, specifically
from certain Labyrinthodonts
• Transition from amphibian to reptile took place during the
Carboniferous period of the earth history
• Of course the final crossing from the amphibians to the reptiles
occurred with the perfection of Amniote Egg
• The oldest known fossil amniote egg is from Lower Permian
sediments in North America
• The appearance of the lower jaw or the migration of the
backboned animals from the water on to the land paved a way
for the success of reptiles on the earth

6. Amniote Egg
The egg mainly consists of:
Amnion : consists of
amniotic liquid
and embryo
Yolk : provides nutrients
to the embryo
Allantois: receives the waste
products produced
by the fetus
Chorion : encloses Amnion, Allantois, yolk and yolk sac
Shell : It is both tough and porous to protect and
exchange O2 and CO2 respectively.

7. CLASSIFICATION OF REPTILES:
Subclasses:
Anapsida-
Proto reptiles which include turtle
Diapsida-
majority of the reptiles, progenitor of birds
Euryapsida-
Plesiosaurs, Placodonts and Ichthyosaurs
Synapsida-
mammal like reptiles, progenitors of
mammals

9. CLASSIFICATION OF REPTILES

11. PICTURE
SHOWING
PTEROSAURS
WHICH HAD
GLIDER WINGS

12. •Pineal foramen, characteristic
of labyrinthodonts persists in
the early reptiles but disappears
with the advancement
• Pterygoid bone of the palate
are prominent in reptiles and in
primitive forms, these bones
carry well developed teeth
•Skull in reptiles is rather deep,
in contrast to the flattened skull
of the Labyrinthodonts
• Primitive otic notch is
suppressed
SKULL
• The occipital condyle is single in
most of the reptiles, a character
that is fore shadowed in the
Anthracosaurs

13. VERTEBRAL COLUMN OF A TYPICAL REPTILE
• The clavicle(collar bone) and the inter clavical bone is present in the
reptilian shoulder girdle which is much reduced as compared with these
elements in the Labyrinthodonts
• Among the primitive reptiles, the ribs form a continuous and generally
similar series from the skull to the pelvis
• Primitive reptiles have two sacral vertebrae wherein amphibians have
only one
• Ilium will be attached to the sacrum
Clavicle
Sacrum

14. LIMBSAND SKINOF REPTILES
•Limb bones are generally
slender than these bones in the
labyrinthodonts
• In the wrist there are never more
than 2 central bones but
labyrinthodonts have 4 central
bones
• 2 proximal bones in the ankle as
contrasted with the 3 in the
amphibians
• The phalangeal formula of
reptiles (seymouria) is 2-3-4-5-3(4)
Skin: It has horny epidermis
folded overlapping scales and
scutes

15. MASS EXTINCTION:
Evolution of reptiles has
been marked by three mass
extinction as shown in the
right.
MESOZOIC ERA
is known as the
age of reptiles.

16. EARTHDURING MESOZOICERA

17. C O N C L U S I O N
• Evolution is the fundamental property of life.
• Evolution of life through ages throw a light on
palaeobiosphere of the past.
• Evolution in all groups of life help in the reconstruction
of the historical geology. In particular the history of the
earth.
• Reptiles will bridge the connection between aquatic
and terrestrial vertebrates. This is the stage where we
can see all the modification.
• Some evolutionary aspects will remain unchanged
even today.
• Reptile evolution can be seen in all the forms of
nature i.e., air, water and on land.

18. •Edwin H Colbert (1969) Evolution of
Vertebrates- Publ. V.R. Damodaran for
Wiley Eastern limited- Second edition- Pp-
110 – 126.
• www.google.com/images
•en.wikipedia.org/wiki/Evolution_of_reptiles