1. Reptiles

2. Class Reptilia

3. General Characteristics of Reptiles
Reptiles are ectothermic, tetrapod vertebrates
They all possess dry, scaly skin
Respiration is by lungs only
Reptiles have a complete or partial 3-4 chambered heart
The skeleton is bony with limbs that lift the body off the ground (except snakes) – limbs are usually paired with 5 digits (pentadactyl)

4. General Characteristics of Reptiles (con’t)
Reptiles are dioecious and fertilization is always internal
No larval stage
The great majority of reptiles are carnivorous although certain turtles & lizards are omnivores or herbivores
Found in many kinds of habitats, from freshwater, salt water, to the driest of deserts. The chief factor that limits their distribution is temperature

5. Class Reptilia Approximately 7000 living species (300 in the US)
There are 4 living orders of reptiles and 15 extinct orders
(dinosaurs)

6. Characteristics that distinguish reptiles from amphibians
Reptiles have tough, dry skin that offers protection against desiccation that is shed periodically

7. Characteristics that distinguish reptiles from amphibians
The shelled (Amniotic) egg of reptiles contains food and protective membrane for embryonic development

8. Characteristics that distinguish reptiles from amphibians
Reptilian jaws are designed for applying force to grip or crush prey. Jaw muscles are much larger & longer

9. Characteristics
All reptiles have some form of copulatory organ for internal fertilization. This is a requirement of a shelled egg because the sperm must reach the egg before it is enclosed in a leathery covering

10. Characteristics that distinguish reptiles from amphibians
Reptiles have a more efficient circulatory system and higher blood pressure than amphibians
Reptile lungs are better developed than amphibians. Reptiles depend on lung respiration exclusively and skin breathing has been abandoned.

11. Characteristics that distinguish reptiles from amphibians
Reptiles have evolved efficient strategies for water conservation. Nitrogenous wastes from the kidneys are excreted as uric acid crystals
Instead of urea or ammonia, so the urine of most reptiles as a semi-solid paste
Uric Acid Crystals

12. Characteristics that distinguish reptiles from amphibians
Reptiles have better body support and more efficiently designed limbs for travel on land

13. Characteristics that distinguish reptiles from amphibians
Reptilian nervous system is much more complex than amphibians. Increased size of the cerebral cortex allows for higher levels of thinking.

14. Order Testudine (meaning a tortoise) approximately 330 species little changed in 200 million years; dinosaur turtle called Archelon

15. General Characteristics
Enclosed in a shell consisting of a dorsal carapace (ribs & vertebrae) and a ventral plastron (sternum)
The shell is composed of an outer horned layer of keratin and an inner layer of bone
Turtles have a poor hearing but a good sense of smell, acute vision and color perception as good as a human
Turtles vary widely in size with the largest weighing 900 kg. and because of their low metabolism they can live more than 120 years
Turtles lack teeth but have horned beak for gripping and tearing food

16. Reproduction Turtles are oviparous with internal fertilization
Amniotic eggs are buried in the ground. In most turtle species, temperature determines the sex of the hatchlings – low temperature produces males and higher temperature produces females. All temperature-dependent reptiles lack sex chromosomes

17. Size & Age
The giant marine turtles may reach 2 meters in length and 725 kg in weight
Low metabolic activity may explain their longevity, believed to exceed years. Even the common Box Turtles live over years

18. Order Squamata
Order Squamata (means Scaly) examples are snakes & lizards
Largest group – 95% of known living species
2 main suborders: Lizards & Snakes

19. Order Squamata Suborder Lacertilia (lizards) – 3300 Species
Examples are geckos, iguanas, skinks, chameleons & monitors
General characteristics
Have moveable eyelids
Teeth present in some species
Scales or epidermal plates
Secrete a highly crystallized uric acid to conserve water
Lizards may deliberately cast off their tails to avoid capture, this adaptation is called autotomy
Lizards store fat in their tail to survive drought

20. Order Squamata Suborder Lacertilia (lizards) – 3300 Species
Examples are geckos, iguanas, skinks, chameleons & monitors
2 Poisonous species in North America
Gila Monster which is found in the SW area of USA
Beaded Lizard which is found in Mexico
Poison is secreted by the lower jaw; lizards do not have fangs
These species are not lethal to humans
Gila Monster
Beaded Lizard

21. Order Squamata Suborder Lacertilia (lizards) – 3300 Species
Examples are geckos, iguanas, skinks, chameleons & monitors
Body Size
Largest is the monitors with the Komodo dragon growing to 12 feet in length
Smallest are the chameleons of 4 cm in length

22. Order Squamata Suborder Lacertilia (lizards) – 3300 Species
Examples are geckos, iguanas, skinks, chameleons & monitors
Other species include –
Iguanas – this group includes the common green iguana, the horned toad which used to be common in Oklahoma and now is considered endangered; Marine Iguanas of the Galapagos Islands which have developed oceanic feeding behaviors
Chameleons – have distinctive adaptive behavior to color change due to chromatophore cells in the skin

23. Order Squamata Suborder Lacertilia (lizards) – 3300 Species
Examples are geckos, iguanas, skinks, chameleons & monitors
Other species include –
Skinks – 14 species live in the USA. Have flat overlapping scales that give a shiny, smooth appearance
Geckos – small agile and nocturnal with adhesive toe pads that allow them to walk on ceilings
Blue Tailed Skink

24. Order Squamata Suborder – Serpentes ( to creep ) – snakes
2300 species, most widespread of all reptiles
General characteristics of snakes –
Snakes are entirely limbless
Skull is highly kinetic which enables them to eat prey several times their own diameter. The lower jaw is loosely hinged and the 2 sides of the mandible are only connected by muscle and skin

25. Order Squamata Suborder – Serpentes ( to creep ) – snakes
2300 species, most widespread of all reptiles
General characteristics of snakes –
The opening (trachea) to the respiratory system is positioned far forward between the mandibles so that the snake can breath while swallowing large prey

26. Order Squamata Suborder – Serpentes ( to creep ) – snakes
2300 species, most widespread of all reptiles
General characteristics of snakes –
The cornea of a snake’s eye is covered by a transparent mambrane called the spectacle

27. Order Squamata Suborder – Serpentes ( to creep ) – snakes
2300 species, most widespread of all reptiles
General characteristics of snakes –
Snakes have a special sense organ called Jacobsen’s Organ which are pits in the roof of the mouth, the tips of the forked tongue fit into these pits and the scent information is transmitted to the brain

28. Snake Movements – 4 types
Lateral undulation –s-shaped – pushes against rough ground or water
Concertina – accordion pleats – folds body & thrusts head forward
Rectilinear – Straight ahead – head lifted – muscle contracts thrusting the head forward (example – Boas)
Sidewinding – sideways looping used by desert vipers – only 2 parts of the body in contact with hot sand at any time
See Page 559 – Figure 26-21

29. Snake Movements
(Sidewinder)
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(Rectilinear)

30. Snakes kill their prey by a variety of methods
Non venomous snakes use suffocation to subdue prey
The Boas and Pythons use this method
Other non venomous snakes that eat specific prey may just bite and swallow; snakes such as bull snakes use this method
Venomous snakes use one of two types of toxins
Neurotoxin acts mainly on the nervous system and paralysis results, shutting down the respiration or heart beat
Hemotoxins break down red blood cells and vessels and result in extensive hemorrhaging of blood into the tissues

31. Poisonous snakes are divided into four families (based on fang type)
Family Viperidae have highly developed retractable fangs at the front of their mouth. This group includes the pit vipers which have heat seeking pits on the front of the rostrum
Examples – rattlesnakes, copperhead, and water moccasin

32. Poisonous snakes are divided into four families (based on fang type)
Family Elapidae have short permanently erect fans and inject poison by repeated bites
Examples are: coral snakes, cobras, black mamba

33. Poisonous snakes are divided into four families (based on fang type)
Family Hydrophiladae are the most high poisonous of all snakes
Example: sea krait

34. Poisonous snakes are divided into four families (based on fang type)
Family Colubridae; this is a very large group and includes most of the non-poisonous snakes but there are 2 deadly snakes in this group and they are rear fanged snakes that use their poison to quiet struggling prey
Examples: African boom-slang & twig snake

35. Antidote for snake bite is called antivenin
Produced by antibodies in the blood from snake bitten or venom injected horses
Antibodies must be specific for the snake bite
The total human death toll from snakebite is about 25,000 each year
The toxicity of a venom is measured by the median lethal dose on laboratory animals, according to this standard, the sea snakes and the venom of the Australian tiger snake appear to be the most deadly but there are more dangerous snakes because of their aggressiveness such as the king cobra (exceeds 5.5 m in lenth) these snakes cause more than 9,000 deaths each year

36. Collection of Snake Venon
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37. Reproduction –
Most snakes are oviparous
The pit vipers are ovoviviparous ( this includes all poisonous American snakes)
The sea snakes are viviparous – live / placental young

38. Order Rhynocephalia (2 living species) the common name is Tuatara
Slow growing animals with a very long life
(Over 80 years)
Many features identical to Mesozoic fossils that are 200 million years old
Has a 3rd eye (pineal eye) with cornea, lens and retina – the function of this 3rd eye is unknown

39. Order Rhynocephalia (2 living species) the common name is Tuatara
Still called by its dinosaur name sphenodon; this animal shows the slowest rate of evolution known among the vertebrates
Has no eyelids
Has hooks on its ribs like birds
Males have 2 penises

40. Order Crocodilia (crocodiles & alligators 25 species
Have remained virtually unchanged for millions of years
There are 3 distinct groups
Crocodiles
Alligators
And the Gavials – found in India
Have a complete secondary palate that allows them to breathe while swallowing food
Alligators are much less aggressive than crocs. The Nile crocodile can grow to over 4000 lbs. and have been known to kill cattle.
They are oviparous and the sex of the offspring is temperature- dependent. High nest temperatures produce males and low nest temperatures produce females and this can result in females outnumbering males 5 to 1

41. Comparison of Crocodiles & Alligators
Narrow Head
Broad Head
Pointed Snout
Rounded Snout
Visible Teeth when mouth is closed
Hidden Teeth when mouth is closed
More Aggressive
Less Aggressive