Vertebrae are procoelous. Alligator mississippiensis (American), A. sinensis (China), Crocodylus palustris (Indian), C. porosus (salt water crocodile of Indo-pacific region), C. niloticus (Nile River), Gavialis gangeticus (Gharials of India, Ganga River). Characteristics of Class Reptilia are given below: 1) Class reptilian (L. Reptilia= creeping) includes animals which are cold blooded. The cloacal opening is longitudinal. Neck, limbs and tails are retractile. These two lines of reptiles became modified for aquatic life in quite different ways but they share the same basic type of skull organisation, with minor differences. An incipient diaphragm is situated between thoracic and abdominal wall. TOS4. Class Aves: Characters and Classification | Animal Kingdom, Class Amphibian: Characters and Classification | Animal Kingdom, Difference between Insect and Spider | Animal Kingdom. 6. 3. These are divided into two major groups- Archosauria and Lepidosauria. There is no metamorphosis, as in the case of amphibians. In the Mesozoic era they were largely replaced by other lines of reptiles such as dinosaurs, but the surviving synapsids gave rise to the mammals. 18. Embryonic Membrane 5. Both Ichthyosaurus and the Plesiosaurus became extinct at the end of the Cretaceous when many other terrestrial reptiles including dinosaurs died out. 2. Sexual reproduction is internal, and sperm may be deposited by copulation or through the apposition of cloacae. The major characteristic feature is the fossa of the temporal region, i.e., behind the orbit, of the skull. Sternal ribs have uncinate process. 6. Twelve pairs of cranial nerves are present. The function of these temporal fossae was probably to enable the jaw muscles to protrude out onto the upper surface of the skull. The lateral line system is altogether absent. 4. They are believed to have evolved from the amphibians millions of years ago. Males are provided with single and median erectile copulatory organ. From this has been derived not only various modern amphibian classes but also the more fully terrestrial populations that do not need to breed in water — they are known as amnoita. This subclass includes three orders — Eusuchia, Rhynchocephalia and Squamata. Most of the ribs are double-headed. Crocodilia e. g., Crocodilus (Crocodile), Alligator, Gavialis (“Gharial”). Nervous system with primitive brain, spinal cord dominant. Diapsida — In this case there are two openings on each side, separated by pos- torbital and squamosal bones. Squamata It in­cludes two suborders: (i) Suborder Lacertilia (Sauria) e.g., Lizards, such as Chameleon (Tree lizard), Calotes (Garden lizard), Hemidactylus (wall lizard). 2) The skin has a few cutaneous glands and high levels of keratin, which prevents water loss through the skin. The major groups of living reptiles—the turtles (order Testudines), tuatara (order Rhynchocephalia [Sphenodontida]), lizards and snakes (order Squamata), and crocodiles (order Crocodylia, or Crocodilia)—account for over 8,700 species. Finally, the tortoises and turtles (Chelonia) have retained, in some respects, the organisation of still earlier times. Order 1. Curator Emeritus, Division of Amphibians and Reptiles, National Museum of Natural History, Smithsonian Institution, Washington, D.C. Fossorial creatures having compact and highly ossified skull. 6) Unlike amphibians, reptiles do not pass through an embryonic stage with gills. They eat fish, birds, turtles, and mammals. They were the most successful and dominant reptiles during the Permian period. Pentadactyle limbs, forelimb possesses webbed digits. It is useful to not only students but also teachers. Urinary bladder may be present. Other features also define the class Reptilia. Most reptiles have a continuous external covering of epidermal scales. Snakes have descended from lizards and there are many similarities between them. Ear drums are slightly depressed. Brain is simple with a very well-developed parietal organ (third eye). (ii) Suborder Ophidia e.g., snakes, such as Naja (Cobra), Bungarus (Krait), Vipera (Viper). 10. Class Reptilia includes many diverse species that are classified into four living clades.Reptilia includes four living clades: Crocodilia (crocodiles and alligators), Sphenodontia (tuataras), Squamata (lizards and snakes), and Testudines (turtles). Cleidoic eggs are large. Development may be internal, with embryos retained in the female’s oviducts, and embryos of some species may be attached to the mother by a placenta. These are chorion, amnion, allantois and yolk sac. General Characteristics of Class Reptilia 2. Content Guidelines 2. Before publishing your Notes on this site, please read the following pages: 1. 5. Rhynchocephalia e.g., Sphenodon (Tuatara)—a living fossil. Chelone = a tortoise): 1. 2. They were fish-like and had single fossa in the skull e.g. I wish you that all your endeavours become fruitful. Species from three of these orders occur in North America: Order crocodilia (crocodilians), Order testudines (turtles) , and … 15. 10. Therefore, several schemes of classification exist. All lizards and snakes are included in this order. 4) Reptiles are considered as tetra pods with two sets of paired limbs. The lower jaw of reptiles is made up of several bones but lacks an anterior coronoid bone. Body varied in shape, covered with horny epidermal scales, sometimes with dermal plates; integument with few glands.

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