VVI Examples of Reptiles for Entrance Exams:
- Turtles
- Tortoises
- Sphenodon (Tuatara)
- Lizards and Snakes
- Draco (flying lizard)
- Heloderma (Gila monster)
- Phrynosoma (Horned toad)
- Chameleon (Color-changing lizard)
- Calotes (Garden lizard)
- Python
- Hydrophis
- Vipers (Vipera)
- Typhlops (Blind snakes)
- Bungarus (Kraits)
- Crocodiles, Alligators, and Gavials or Gharials
General Characters of Reptiles
· Evolved during the carboniferous period and flourished well in the Jurassic period of the Mesozoic era ® also known as the Golden age of reptiles.· Basically terrestrial. Few are secondarily aquatic. Poikilothermic.
· Skin is dry and is covered by epidermal scales or plates. No glands in the skin (Exception: Femoral glands in male lizards).
· Respiration by lungs.
· Generally 3-chambered heart with incompletely divided ventricle. But, Crocodiles have a 4-chambered heart.
· Renal portal system reduced, the first appearance of the hypophyseal portal system.
· Monocondylic skull. All vertebrae are procoelus.
· Presence of 3 chambered cloaca.
· Uricotelic mode of excretion, metanephric kidney.
· Presence of 12 pairs of cranial nerves.
· Sexual dimorphism present. Oviparous. No larval stage in development.
· Egg is cledoic, macrolecithal and telolecithal egg.
· Cleavage is meroblastic.
· Amniota (i.e. extraembryonic membranes present). Classification and Examples
SOME IMPORTANT NOTES ON SNAKES
a) Body covered with small horny scales known as ‘ventrals’ on the ventral surface and ‘shields’ on the head.b) Fangs: Modified maxillary teeth.
c) Poison glands: Modified salivary (parotid) gland.
d) Eyes: Circular and covered with transparent scale.
e) Tongue: Long, slender, and forked at the tip. NOT concerned with a taste sensation. Rather it is concerned with the sense of smell. Particles floating in the air are picked up by the tongue and conveyed to the olfactory organ (known as Jacobson's organ) at the roof of the mouth that is concerned with the smell.
f) Snake venom: Maybe myotoxic, hemotoxic, or neurotoxic.
Sea snakes: Myotoxic
Vipers: Hemotoxic
Cobra, Krait: Neurotoxic
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g) Hood of cobra (Naja naja) is formed by expansion of cervical ribs.
h) Chameleon- color changing and viviparous lizard
i) Python is the largest non-poisonous and viviparous snake.
j) Foramen of Panizza is the aperture present in the heart of the crocodile.
k) Mesozoic era is the golden age of Dinosaurs.
Classification of Reptiles
This classification is based on the temporal fossa on the skull.1. Subclass - Anapsida
2. Subclass – Diapsida
It is divided into 4 order
They are primitive reptiles that have solid skulls without temporal openings.
Order – Chelonia or testudinata
· It includes turtles (aquatic form), tortoises (terrestrial form), and terrapins (edible freshwater form)
· Body is covered by dorsal carapace and ventral plastron.
· Sternum is absent.
· Limbs has claws or webbed feet or flippers
Order – Chelonia or testudinata
· It includes turtles (aquatic form), tortoises (terrestrial form), and terrapins (edible freshwater form)
· Body is covered by dorsal carapace and ventral plastron.
· Sternum is absent.
· Limbs has claws or webbed feet or flippers
Differences between turtles and tortoises
| S.N | Turtles | Tortoises |
|---|---|---|
| 1. | Mostly live on the sea | Mostly terrestrial form or found in freshwater also. |
| 2. | All are herbivores | Maybe herbivores |
| 3. | Limbs have 4 or 5 digits with claws | Limbs are modified into paddles or flippers for swimming. |
| 4. | The neck is long, the head can be withdrawn completely inside the carapace | The neck is short. The Head can not be completely withdrawn inside the carapace. |
| 5. | The carapace is oval and high | The carapace is heart-shaped and low |
2. Subclass – Diapsida
It is divided into 4 order
A. Order – Rhynchocephalia
· All are extinct except Sphenodon. Commonly called a tuatara.
· Sphenodon is burrowing carnivorous and nocturnal in habit.
· Presence of pineal or third eye.
· It is also known as a living fossil because it shows the characteristics of stem or fossil reptiles or connecting link between amphibia and reptile.
· All are extinct except Sphenodon. Commonly called a tuatara.
· Sphenodon is burrowing carnivorous and nocturnal in habit.
· Presence of pineal or third eye.
· It is also known as a living fossil because it shows the characteristics of stem or fossil reptiles or connecting link between amphibia and reptile.
B. Order – Squamata
· Commonly called Lizards and Snakes
DIFFERENCES BETWEEN LIZARDS AND SNAKES
| S.N | Lizards | Snakes |
|---|---|---|
| 1. | They have pentadactyle limbs with four claws except for the Ophisaurus (limbless lizard), anguis and rhineura and barkudia | They are limbless. |
| 2. | Their tails show autotomy | But not show autotomy. |
| 3. | Eyelids are movable and present in the nictitating membrane. | The eyelids of snakes are immovable and have no nictitating membrane. |
| 4, | These are present. | Sternum, pectoral girdle, tympanum, and urinary bladder are absent. |
| 5. | Mostly non-poisonous if poisonous its poison is neurotoxic. | Poison is neurotoxic as well as haemotoxic. |
| 6. | Eg . Draco (flying lizard), Heloderma (Gila monster is only poisonous lizard) Viviparous lizard is Phrynosoma (Horned toad) and Chameleon (colour-changing lizard), Calotes (Garden lizard) |
Eg. largest non-poisonous snake – python; Viviparous snakes- sea snakes (Hydrophis) and vipers (Vipera), typhlops ( blind snakes) Bungarus ( kraits). |
| 7. | Both lungs are equally developed. | The left lung is greatly reduced. |
| 8. | Premaxilla bears conical teeth. | Premaxilla is toothless. |
· Commonly called crocodiles, alligators, and gavials or gharials.
· They are large-sized, carnivorous and aquatic reptiles
· Tail is laterally compressed.
· Teeth numerous, thecodont and heart is 4 chambered.
· Pineal gland is absent
· Lungs cavity is separated by the muscular diaphragm to body cavity which is analogous to mammals.
· Presence of Foramen panizzae in crocodiles and lizards which is the aperture present between left and right aortic cross.
DIFFERENCES BETWEEN CROCODILES, ALLIGATORS, AND GAVIALS
| Crocodiles | Alligator | Gavials |
|---|---|---|
| They are found in Asia, Africa, Central America. Indonesia, Malaya, North Australia. | They are found in North America and China. | They are found in India and Nepal. |
| The body is olive green with black spots or bands. | Body colour is steel grey. | Body colour is dark olive green. |
| The snout is moderately long and pointed. | The snout is broad and rounded. | The snout is very long and slender. |
| Body length is about 8 meters. | The body is about 3 meters. | The body is about 6 meters. |
| Teeth range from 18 to 19 in number. | Teeth range from 17 to 22 in number. | Teeth range from 27 to 29 in number. |
| Their mandibular rami united up to the 8th tooth | Their mandibular rami united up to 5th tooth 14th tooth | Their mandibular rami united up to the 14th tooth |
| 4th mandibula tooth is visible externally | 4th mandibular tooth is not visible externally | absent |
| They are more aggressive and can attack human. | They are less aggressive. | They can only feed upon fish due to their smaller throat size. |
D. Order – Parapsida (Extinct Reptiles or Dinosaurs)
· They were large and heavy.
· They were originated in the Triassic period and got extinct in the cretaceous period of the Mesozoic era.
· Therefore Mesozoic era is the golden age of reptiles.
· The Thecodontia at the end of the Triassic period gave rise to dinosaurs such as allosaurus, pterosaur, etc.
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