Reptiles class
- 1. Priyanka Rani Majumdar Lecturer Dept. of FIMS NSTU
- 2. Class Reptilia • L. repere, creeping • Terrestrial tetrapods • Cold blooded, limbs 2 pairs; Skin dry and devoid of glands • Respiration by lungs • Covered by ectodermal horny scales or bony plates • Body divisible into head, neck, trunk and tail • Heart usually 2-3chambered except crocodiles • Amniote (shelled) egg with extra-embryonic membranes (gas exchange, waste storage, nutrient transfer) • Fertilization internal. Mostly oviparous e.g. snake, crocodiles, turtles
- 3. Classification Reptiles are grouped into approximately 16 orders of which only 4 are living. On the basis of absence or presence of certain openings through the posterolateral or temporal region of the skull I. Subclass Anapsida II. Subclass Euryapsida III.Subclass Parapsida IV.Subclass Synapsida V. Subclass Diapsida
- 5. Order 1. Chelonia or Testudinata Gr., chelone, turtle; L., testudo, turtle Body short, broad and oval Limbs clawed and webbed, paddle-like Body encased in a firm shell of dorsal carapace and ventral plastron, made of dermal bony plates Thoracic vertebrae and ribs usually fused to carapace Teeth absent. Jaws with horny sheaths. e.g. Chelone, Testudo Subclass 1. Anapsida Primitive reptiles with a solid skull roof. No temporal openings
- 6. Subclass 2. Euryapsida (extinct) Skull with a single dorso-lateral temporal opening on either side bounded below by postorbital and squamosal bones Subclass 3. Parapsida (extinct) Skull with a single dorso-lateral temporal opening on either side bounded below by the supratemporal and postfrontal bones. Subclass 4. Synapsida (extinct) Skull with a single dorso-lateral temporal opening on either side bounded above by postorbital and squamosal bones
- 7. Subclass 5. Diapsida Skull with two temporal openings on either side separated by the bar of postorbital and squamosal bones Order 2. Rhynchocephalia L., rhynchos-snout and Gr., kephale-head Body small,elongated and lizard-like Limbs pentadactyle, clawed and burrowing Exoskeleton of granualar scales and a mid dorsal row of spine Skull diapsid Teeth acrodont i.e. attached on the top surface of the jaw bone Cloacal aperture transverse No copulatory organ in male e.g. Sphenodon punctatum (Tuatara)
- 8. Order 3. Squamata L., squama-scale Small to medium, elongated Limbs clawed, absent in snakes and few lizards Exoskeleton of horny epidermal scales, shields and spines Teeth acrodont or pleurodont i.e. on the inner side and upper side of the jawbone Cloacal aperture transverse Male with eversible double copulatory organs (Hemipenes) Divided into two suborder-Lacertilia and Ophidia e.g. Lizards and snakes
- 10. Order 4. Crocodilia Gr., Krokodeilos- Crocodile Large-sized, carnivorous and aquatic reptiles Limbs short but powerful, clawed and webbed Skin thick with scales, bony plates and scutes Teeth numerous, thecodont, lodged in sockets Cloacal aperture is a longitudinal slit Male with a median, erectile, grooved copulatory organ (penis) e.g. Crocodylus, Gavialis, Alligator
- 12. Sphenodon punctatum (Tuatara) It is a single living species under the order Rhynchocephalia, commonly called Tuatara, found only in New Zealand. It is referred to as a living fossil because it has retained many primitive characteristics of stem reptiles i.e. Anapsida It is burrowing, carnivorous and nocturnal in habits Lives in small holes or burrows in rocks associated with petrels or in water. Feeds largely on small invertebrates (worms, insects, spiders, molluscs), fish, gecko During the day it basks in the sun to raise its body temperature It lays about 10 eggs with white egg shells in spring in holes in ground which require more than a year to develop and hatch Life span in captivity is 50 years
- 14. Lacertilia Ophidia Body elongated, lizard-like Body slender, narrow, snake-like Limbs and girdles usually well-developed Usually absent, vestigial hindlimbs and pelvic girdle in boa, python etc. Eyelids movable. Nictitating membranes present Eyelids fixed. Nictitating membranes absent Ear openings and tympanum present Auditory openings and tympanum absent Mouth non-expansible because two rami of mandible firmly united Mouth expansible because mandibular rami joined by an elastic ligament and can be widely separated during swallowing of large prey Tongue rarely notched or extensile Tongue slender, bifid and extensile The ventral side of the body is covered by the small scales The ventral side of the snake’s body is covered by the large shields
- 16. Crocodiles Alligators Gavials or Gharials Crocodiles or true Crocodiles are included in the family Crocodylidae and subfamily Crocodylinae An alligator is a crocodilian of the family Alligatoridae Gavials or Gharials is a crocodilian of the family Gavialidae More aggressive. Dangerous to man Less aggressive. Attack man in self- defense if provoked They can eat only fish because of narrow throat. They also known as the fish-eating crocodile Moderately long and V-shaped snouts Short broad and U-shaped snouts Very long and slender for their piscivorous diet The upper and lower jaws of crocodiles have same width. An alligator’s upper jaw is wider than its lower jaw The upper and lower jaws of Gavials have same width. When mouth is closed, Many interlocking teeth are visible When mouth is closed, only the top teeth are visible When mouth is closed, Many interlocking teeth are visible males growing much larger and more rapidly than females Male and female alligators can be hard to tell apart visually Sexes of gavials are separated easily by the presence of bulbous growth on the tip of the mature male’s snout which is looking as like as earthen pot known locally as 'ghara' Crocodiles can move by ‘belly-run’ and ‘high walk’ where the body is raised clear of the ground Crocodiles can move by ‘belly-run’ and ‘high walk’ but cannot walk on their hind legs for long distances do not have the ability to raise the body off the ground or to produce the "high-walk" and can only move in a forward "sliding" motion on land
- 20. Turtle Tortoise Mostly aquatic, especially in seawater Terrestrial Streamlined carapace The carapace of tortoise is rounded and domed A turtle cannot retract their heads and flippers into their shells They can completely retract their heads and legs into their shells They have webbed feet and the feet become long flippers in the case of sea turtles They have short, thick and stumpy feet for walking and their feet have claws for digging They are good swimmers They aren’t good swimmers They are heavy and cannot lift their bodies off the ground when crawling They can lift their bodies off the ground when crawling Mainly omnivorous Mainly herbivorous
- 22. Origin of Reptiles The primitive reptiles originated from some primitive labyrinthodont amphibia in the beginning of Carboniferous period About 250 years ago, some labyrinthodont amphibians gradually took on reptilian characteristics, which are called stem reptiles. These reptiles are belong to the order Cotylosauria of the subclass Anapsida Seymouria, one of the members of the Cotylosauria found in the Texas, perhaps 250 million years ago Seymouria is a connecting link between labyrinthodontia and Cotylosauria because the structure of Seymouria was intermediate between the amphibians of that time and the early reptiles
- 23. Resemblance of Seymouria with the amphibia Skull is flat An intertemporal bone is present Teeth are labyrinthine and also found on vomers and palentines Neck is short Resemblance of Seymouria with the reptilian Limbs are muscular and arise mid-ventrally Skull is anapsid Pelvic girdle is attached to vertebral column by sacral vertebrae
- 24. Adaptive radiation Adaptation or adaptive radiation is a evolutionary process in which organisms diversify rapidly into a multitude of new forms, as a result of natural selection so that it adjusts to new or altered environmental conditions or able to live in its habitat or habitats. Adaptation may cause either the gain of a new feature, or the loss of an ancestral feature for the competition for food and living space The adaptive radiation of reptiles took place twice, first in the Palaeozoic and secondly in the Mesozoic
- 25. Palaeozoic radiation: The ancestral reptiles or cotylosaurs multiplied rapidly all ecological niches Their radiation involved adaptations to different methods of locomotion and feeding The synapsida- Pelycosauria and Theromorpha were similar to cotylosaurs. Later Therapsida which had different dentition and improved locomotion as nearly like as mammals
- 27. Mesozoic radiation: The ancestral cotylosaurs had disappeared at the end of the palaeozoic, but their descendants produced a second and bigger radiation during Mesozoic Throughout the Mesozoic era, the reptiles dominated not only the land but also the sea and the air. The Mesozoic era is called as the age of reptiles The reptiles ruled the earth over a great span of time, about 130 million years The extinct reptiles are represented by as many as 16 orders- one led to the birds, one to the mammals and four to the modern reptiles Mesozoic reptiles were disappeared at the beginning of the Cenozoic era, leaving behind the representatives of only 4 living orders.
- 28. Euryapsid line: The euryapsids or Plesiosaurs were large, marine, turtle-like, heavy- bodied and long-necked creatures and fish-eaters which were extinct towards the end of the Cretaceous Parapsid line: As like as Euryapsida, another marine blind alley was fish-like or porpoise like Ichthyosaurs
- 29. Diapsid line: Divided into two branches-Lepidosauria and Archosauria Lepidosauria were probably ancestor of the modern Squamata (snakes and lizards) and Rhynchocephalia (Tuatara) Archosauria were the ruling reptiles of the Mesozoic era and represented the extinct Pterosauria, the extinct Dinosaurs and the modern Crocodilia and the modern birds Pterosauria were the extinct flying reptiles which are the ancestors of the modern birds
- 30. Transitional fossils Many fossils show a clear transition from one species, or group, to another. Archaeopteryx was found in Germany in 1861. It share many characteristics with both reptiles (such as a long, bony tail and conical teeth) and birds (such as feathers and a wishbone). Archaeopteryx suggest that birds were evolved from animals like reptiles. Archaeopteryx
- 31. Dinosaurs: At the end of Triassic, Thecodontia, the early descendants of Archosauria, gave rise the dinosaurs which means terrible lizards Subdivided into two orders depending on the structure of their pelvis-Saurischia and Ornithischia.
- 33. Adaptive radiation in reptiles
- 35. Convergent evolution is the process whereby organisms not closely related (not monophyletic), independently evolve similar traits i.e. analogous structures as a result of having to adapt to similar environments or ecological niches. Divergent evolution is the evolutionary process in which a single ancestral species evolves into different forms or new species which occupy into different or isolated habitats or environments
- 36. Convergent evolution Divergent evolution Species are unrelated Species are closely related Different ancestor Common ancestor Converge to produce analogous structures (common usage) Diverge to produce homologous structures (Same structure) Species appearance becomes more similar over time Species appearance becomes more different over time e.g. wings in birds, insects and bats e.g. Pentadactyl limb structure