Reptiles

Reptiles
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Evolutionary Perspective
Reptiles were first vertebrates that possess amniotic eggs

Amniotic egg have extra embryonic membranes
Those membrane perform following functions
1. These protect embryo from desiccation
2. These support the embryo like cushion
3. These membrane promote gas transfer
4. These membrane remove waste material
Amniotic egg structure
 Shell: birds and reptiles have hard or leathery shell. This shell
protect the developing embryo
 Albumin: the albumin cushion the embryo. It also provide
moisture and nutrients to the embryo

 Yolk: the yolk supply food to the embryo
 The amniotic egg is the major synapomorphy
 It distinguishes the reptiles, birds and mammals from non amniotic
vertebrates
Adaptive radiation in reptiles
 Adaptation: characters change according to surrounding environment

 Radiation: Formation of many species from one common ancestor
 “It is differentiation of a single ancestor into many species hat cause

different morphological and physiological traits according to their
habitat”
Groups of Reptiles
 Three groups of reptiles
 Anapsid
 No posterior lateral opening
 Turtles
 Diapsid: 2 postero lateral openings
 2 subclases 1. leidousoria snakes, lizards, tutara)
 2. Archosouria: dinosours
 Living archosours are crocodiles
Synapsid
 One opening in temporal region

 All of synapsid become extinct
 It give rise to mammals
Characteristics of reptiles
 Their surface has one surface condyle for articulation with the first
neck vertebrae
 Respiration takes place by lungs
 They have internal fertilization and amniotic egg
 Reptiles have dry skin. It has keratinized epidermal scales. Keratin
is a resistant protein. It is found in epidermal derived structures of
amniotes. It is chemically bounded to phospholipids. Therefore, it
prevent loss of water through body surface
 They are found in all continent except Antarctica. However they are
most abundant on tropical and subtropical environments.
Orders
ORDER TESTUDINES
Turtles (L. testudo, tortoise)
Teeth are abundant in adults. The are replaced by a horny beak. They have
keratinized beak
They have short broad body
Their shell consist of dorsal carapace and ventral plastron
Turtles have 225 species. They have a bony shell
Their limbs articulate internally with the ribs
Example: turtle
Shell in turtle:
Carapace: the dorsal portion of the shell is the carapace. Carapace is formed
by the fusion of vertebrae, ribs and bones in the dermis of skin. Keratin
cover the bone of the carapace
Plastron: the ventral portion of the shell is plastron.
It is formed from bones of the pectoral girdle and dermal bone
Keratin also cover it
The shell of some turtle have flexible area or hinges
These hinges attach the anterior and posterior edges of the plastron
The hinges close the opening of the shell during withdrawal of body into the
shell
Turtle have eight cervical vertebrae
These vertebrae articulated to form an S shaped structure
It draws the head in to the shell
Reproduction and life span
 Long life pan
 Most reach at sexual maturity after seven or eight years
 They can live 14 or more years
 The age of large tortoise
 Age of tortoise of Galapagos island may be above 100 years
 All turtles are oviparous
 Female use their hind limbs to dig nest in the soil
 There they lay eggs
 Their clutches contain 5 to 100 eggs
 They cover eggs with soil
 Development takes from 4 months to one year
 Parent does not attend o the egg during this time
 The young are independent of the parent at hatching
Turtle in danger
 turtle have slow rate of growth
 They have long juvenile period
 They have high mortality rate
 The turtle are becoming extinct
 Dogs and other animals are hunting young turtles
 It has severely threatened some species of turtle
 They make nest on certain beaches years after year
 Observation program of sea turtle is difficult
 The have rage of thousands of kilometer of ocean
Order Renchocephalia
 Rhynchos, snout + kephole, head
 Renchocephalia has only one surviving species
called tuatara (Sphenodon punctalus)
 It is lizard like reptile
 It has remain unchaged since it eveolved from
extinct relatives ere present at the begening of
mesozoic era, nerly 200 myo
Distinct features
 Tooth attachment and structures distinguish the tuatara from other
reptiles.
 They have two rows of teeth on upper jaw and single row of teeth in the
lower jaw
 They bite the bird with these teeth
 This biting can decapitate a small bird
 It was widely distributed in Newzeeland
 The population of tuatara is affected b human influences and domestic
animals
 It is now present in far of offshore islands
 It is protected by Newzeeland law
 It is oviparous and it share underground burrows with ground nesting
seabirds
 Tuatara come out of their burrows at dusk and dawn
 They feed on insects or sometime on vertebrates
Order Squamata
 Snakes, lizards
 Squamas, scale + ata hear
 They have specific character of skull and jaw
 They are more successful and diverse group of living reptiles
 Example: snakes, lizards
Sub orders
 Order Squamata has three suborders

 1. Sauria (Lizards)
 2. Serpents (Snakes)
 3. Amphisbeania (worm lizards)
Sub order Sauria
 Lizards
 3,300 species
 Two pair of legs
 Few lizards are legless
 Vary in size
 Few cm to 3m
 Most are oviparous
 Some are oviparous or ovoviviparous
 They deposit eggs under rocks or debris or in
burrows
 Geckos
Commonly found on the walls of houses

Body is short and stout
They are nocturnal
They produce sound of clicking
They have large eyes
Their pupil contract and narrow during the day and
widen at night
they have adhesive disk on their digits
these disk help in clinging to the tree and walls
Iguanas
Iguanas have heavy body
They have short neck and distinct head
this group include marine iguana of
galapagos Island and flying dragon of south
east Asia
Draco has lateral fold of skin
It is supported by ribs
The ribs of Draco expand to form a gliding
surface it can glide 30 m or more
 Chameleons
It is another group of iguana
It is found in Africa and India
Chameleon are adapted for arboreal
lifestyles
They use long sticky tongue to capture
insects
Anolis the pet store chameleon is as known
as iguanid

Reptiles

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Reptiles

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Reptiles

Reptiles were first vertebrates that possess amniotic eggs

moisture and nutrients to the embryo

 The amniotic egg is the major synapomorphy

 It distinguishes the reptiles, birds and mammals from non amniotic

 Adaptation: characters change according to surrounding environment

 “It is differentiation of a single ancestor into many species hat cause

 One opening in temporal region

 Order Squamata has three suborders

 Two pair of legs

 Few lizards are legless

 Most are oviparous

 Some are oviparous or ovoviviparous

 They deposit eggs under rocks or debris or in

Commonly found on the walls of houses

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