Reptilian characters

reptilian characters

1. General Characteristics of Reptiles B.Ashok Kumar Lecturer in Zoology KRK Govt Degree college Addanki-523201 Contact me @9652929696 Mail me : [email protected]

2. Diverse group of animals Lizards Snakes Tortoises Crocodiles Extinct dinosaurs etc. REPTILES

3. REPTILES From a latin word " reptilis " meaning " creeping“ Repere or reptum means creep/ crawl

4. Herpatology - study of reptiles Smallest reptile- dwarf gecko Sphaerodactylus aurieus (16mm) Largest reptile living- Crocodylus porosus (20.6 feet, over 1900kgs) Golden age of reptiles - Mesozoic era REPTILES

5. First vertebrates which became independent of water and took possession of dry land REPTILES …

6. Complete colonization of land was achieved by the reptiles, which can lay their eggs on dry land . Amniotes-Amnion and allantois REPTILES …

7. Originated in Carboniferous period from labyrinthodont Amphibian stock Flourished during Mesozoic era- Golden age REPTILES …

8. Terrestrial organisms Poikilotherms Tetrapods - pentadactylous limbs Digits end in claws Characteristics of reptiles …

9. Body -head, neck , trunk and a tail Body –dry, water proof epidermal scales-epidermal in origin, osteoderms beneath horny scales- crocodiles Skin – few glands(musk glands, femoral glands, etc) or no glands Dermis - chromatophores Characteristics of reptiles …

10. Skull bears single condyle One or two temporal fossae are usually found Pineal foramen is present in the skull Teeth are simple, conical and thecodont Ribs single headed Gastralia (abdominal ribs) rob like membrane bones - ventral body Characteristics of reptiles …

11. Coelom-Pericardial cavity & Pleuro peritoneal cavity Dentition Homodont, Acrodont and polyphyodont Characteristics of reptiles …

12. Pulmonary respiration i.e. respiration through lungs takes place Intercoastal muscles assist in respiration Cloacal respiration – turtles Cutaneous gas exchange in many turtles, sea snakes Characteristics of reptiles …

13. Heart consists of a sinus venosus, 2 auricles and 1 incompletely divided ventricle Has both left and right systemic arches Hepatic and Renal portal systems RBC-Oval and Nucleated Characteristics of reptiles …

14. Metanephric kidneys with no nephrostomes Uricotelic Cloaca with three chambers- Coprodaeum (opening of large intestine), Urodaeum (openings of the Excretory and genital ducts)& Proctodaeum opens out by cloacal aperture Characteristics of reptiles …

15. Two meninges- the duramater and the pia-arachnoid membrane 12 pairs of cranial nerves seen Tympanic membrane in external auditory meatus, middle ear with single ossicle - Columella auris Third eyelid nictitating membrane present in most In Snakes-Jacobson’s organs ( vomeronasal organs) Characteristics of reptiles …

16. Sexes are separate Males possess copulatory organs Fertilization is internal Large eggs with considerable yolk Eggs covered by porous calcareous shell( cleidoic & megalecithal ) Cleavage - meroblastic Characteristics of reptiles …

17. REPTILIAN EGGS …

18. Embryo develops within embryonic membranes – amnion and allantois Most reptiles are oviparous Some snakes are viviparous Characteristics of reptiles …

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