• Reptiles
• There are 8900 species of reptiles
• Reptiles live on every continent but Antarctica
• World’s smallest reptile: dwarf gecko 16 millimeters in length
• World’s largest LIVING reptile: Australian saltwater crocodile 23 feet long
• Worlds largest reptile EVER: Argentinosaurus 130 feet long and 110 tons in weight

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• Where did reptiles come from? That’s complex.
• 340 million years ago the amniotes evolved
• Amniotes – organism whose young develop within an amniotic layer
• The amniote egg is waterproof, not airproof. So the young can still breathe
• As a result, amniotes can stay in the egg longer so the young hatch fully formed (no tadpoles)
• By 300 million years ago the amniotes had split into three distinct groups
• Anapsids – turtles are a living example
• Diapsids – lizards, snakes, crocodilians, and birds
• Synapsids – mammals are a living example
• The main difference between the three groups is the way their skulls are built

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• Novel adaptations of reptiles (or in other words what makes reptiles different from amphibs)
• In general, reptiles are better at conserving water than amphibians
• Shelled, waterproof eggs
• Internal fertilization – how does that save water?
• Waterproof keratinized skin
• Keratin is a protein that makes up skin, feathers, claws, beaks, hair, and turtle shells
• Kidneys developed to conserve water
• Fish and amphibians have kidneys, but they do not preserve water
• Reptiles (and birds) form uric acid, allows them to get rid of wastes with less water loss

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• Reptiles have waterproof skin, which is an advantage for conserving water, but there is a downside. What is the disadvantage of waterproof skin?
• Because reptiles cannot breathe through their skin, suddenly the three chambered heart becomes a major disadvantage
• Reptiles are the first group to develop the 4 chambered heart
• Crocodilians have a 4 chambered heart, other reptiles have a three chambered heart with a larger ventricular septum
• Blood flow in a 4 chambered heart: right atrium – right ventricle – lungs – left atrium – left ventricle - body

• The Jacobson’s organ – this is why reptiles have those forked tongues
• Officially called the Vomeronasal Organ (VNO)
• Function – the VNO is used to detect pheromones and for smell
• Pheromones – chemical messages sent between individual animals
• So why the forked tongue? The each reptile has 2 VNO located in pits in the roof of the mouth
• The scent particles bind to the tongue and the reptile puts the tips of its tongue into the VNO pits
• VNO is found in all reptiles and most mammals
• A big debate among scientists if the VNO is a vestigial organ in humans

• One MAJOR difference between reptiles and every other animal
• Sex determination in many reptiles is temperature dependent
• Example: American alligator
• Eggs incubated at 86 degrees or cooler will all be female
• Eggs incubated at 93 degrees or warmer will all be male
• Eggs incubated between 86-93 degrees will be a mix of male and female

• For almost 100 years, reptiles and amphibians were classified into the same group of animals.
• Differences between Reptiles and Amphibians:
• Reptiles lay a shelled, waterproof egg
• Reptiles have much stronger jaws than amphibians capable of crushing prey
• Reptiles have a copulatory organ which allows for internal fertilization
• Copulation – to mate

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• Reptiles have a more efficient circulatory system with higher blood pressure (why would reptiles need higher blood pressure than amphibians?)
• Reptiles have more efficient lungs than amphibians (why do reptiles need better lungs)
• Reptiles have stronger limbs and are more efficient at land travel than amphibians
• The reptilian brain and nervous system is more complex with a larger brain than amphibians.

• Six main groups of reptiles
• Testudines (Turtles)
• Sauria (Lizards)
• Amphisbaenia (Worm lizards)
• Serpentes (Snakes)
• Sphenodonta (Tuatara)
• Crocodilia (Alligators and crocodiles)

• Testudines (Turtles and tortoises)
• Approximately 300 species
• World’s smallest turtle: Speckled Padloper Tortoise
• 3.1 inches long and 4.9 ounces (1/3 of a pound)
• World’s largest living turtle: Leatherback sea turtle
• 6 feet 6 inches long and 2,000 lbs
• Largest turtle in the North America: Alligator snapping turtle
• 2.6 feet long and 130 lbs
• Largest turtle EVER: Archelon 13.5 feet long

• Characteristics of Testudines
• Turtles have existed, almost unchanged, for 215 million years
• Can be terrestrial, aquatic, or both
• Hard outer shell (wonder what its made of?)
• Turtle shells are actually the turtle’s ribs fused together
• The shell provides protection, but what are the disadvantages of the shell?
• Slow movement (Galapagos turtles move at 300 yards per hour)
• Take a deep breath, what’s another disadvantage of the shell?
• The shell inhibits breathing

• Characteristics of Testudines (continued)
• Poor hearing, as a result most testudines are completely mute
• Testudines have excellent smell and vision
• General rule, if an animal has any one really developed sense, it will have another less developed sense
• Examples:
• Dogs – great smell and hearing, poor eyesight
• Birds – great eyesight, poor smell
• Take home message: nature doesn’t waste energy
• Testudines are long lived – some tortoises are 150 years old (musket ball)

• Sauria (Lizards)
• 5079 species
• World’s fastest lizard: Black Spiny-tailed Iguana
• Top speed of 21.7 mph
• Worlds smallest lizard: Pygmy Gecko 0.75 inches
• World’s largest living lizard: Komodo dragon
• Up to 10 feet in length and 150 lbs
• Largest lizard in North America: Gila monster
• 2 feet in length and venomous
• Largest lizard ever: Megalania
• 85 feet long

• Characteristics of Lizards
• Can be terrestrial, arboreal, burrowing, aquatic, and aerial
• Can be carnivorous or herbivorous
• Excellent sense of sight, poor hearing
• Most lizards communicate through color and postures
• Many lizards can change color
• Some have detachable tails (most lizards store fat in their tails)

• Main Groups of Lizards
• Geckos
• Mostly nocturnal
• Have toe pads that let them walk on any surface
• Only group of lizards that can vocalize
• Skinks – closest relatives to snakes
• Round body with small legs
• Most skinks are burrowing by nature
• Almost half of all skinks are viviparous – meaning they give birth to live young = no egg laying
• Chameleons
• Mostly arboreal
• Can change colors
• Have no ears = deaf
• Have a prehensile (gripping) tail
• Independent eye control
• Iguanas – largest group of lizards (this is kind of the dumping ground)
• Have a parietal eye – light sensitive spot on top of the head
• The parietal eye sets natural day/night rhythms

• Serpentes (Snakes, did I really have to tell you that one?)
• 3,100 species, 375 are considered deadly venomous
• World’s smallest snake: Leptotyphlops carlae
• 3.9 inches long
• World’s largest snake: Python
• 49 feet long and 990 pounds
• Largest snake ever: Titanboa
• 50 feet long, 2,500 lbs, and 3 feet in diameter
• World’s most venomous snake: Inland Taipan of Australia
• One bite has enough venom to kill 200 humans
• World’s fastest snake: Black Mamba
• 12 mph (oh and the black mamba is one of the world’s top 5 most poisonous snakes, makes you want to stay the HELL out of Africa doesn’t it?)
• Largest N. American snake: Eastern Diamondback rattler
• 8 feet and 15 lbs

• Characteristics of snakes
• No legs (duh) and no ears
• However snakes are not deaf, they sense vibrations with their bodies
• No eyelids – eye is protected by a transparent layer
• Jaws are only connected by muscle and skin allowing for massive stretching
• A moveable windpipe that allows them to breath while swallowing prey
• Ability to see infrared light

• Amphisbaenia: Worm lizards
• Legless burrowing lizards
• Most are less than 6 inches long
• Heavily constructed skull that allows for digging
• Really don’t know much about them.

• Sphenodonta: Tuatara (I know it looks like a lizard, give me a moment)
• 2 feet in length, weighing up to 2.2 lbs
• Regarded as a “living fossil”
• Tuatara’s split from the ancestors of lizards and snakes 200 million years ago and have changed little since then
• Have the most primitive heart of all reptiles
• Only have one lung
• Have no ears, but can hear
• Well developed parietal eye
• Low body temperature 51 degrees = slow growth rate
• Takes 10 years to reach sexual maturity, mate once every 4 years.

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• Crocodilia – Crocodiles, Alligators, Caimans, and Gharials
• 23 species. Closest living relatives to birds
• World’s smallest crocodilian: Cuvier’s Dwarf Caiman
• Males: 5.2 feet. Females 4 feet
• World’s largest living crocodilian: Saltwater Crocodile
• 23 feet long and over 2,500 lbs
• Largest crocodilian ever: Sarcosuchus imperator
• 40 feet long, 8 tons
• Largest crocodilian in North America: Alligator
• One caught in 1890 was 19 feet long and 2,200 lbs

• Characteristics of Crocodilians
• 4 chambered heart
• Only reptile without a Jacobson’s Organ = poor sense of smell
• Teeth that continually grow and replace (A crocodile may go through 3,000 teeth in its life)
• Are able to move air in their lungs to affect buoyancy
• Digestive system is similar to birds, two chambered stomach
• Crocodilians have the most powerful stomach acid in the world, EVERYTHING from their prey is dissolved

• Alligator vs. Crocodile
• Alligators have a “U” shaped snout, crocodiles have a “V” shaped snout
• Alligators are usually darker in color
• The 4^th tooth of crocodiles is visible when their mouth is shut
• Whats the big deal?
• Crocodiles have a more powerful bite
• Crocodiles are more aggressive than alligators

• Lets talk about venom – evolved snake saliva
• Venomous snakes are divided into two groups based on their fangs and the type of venom they use
• Vipers
• Example: rattlesnakes
• Elapid
• Example: cobras
• Vipers have a cytotoxic venom which kills red blood cells and other cells
• Death comes as a result of low blood pressure from internal bleeding and organ damage
• Elapids have a neurotoxic venom which kills nerve cells
• Death comes for paralysis of the diaphragm leading to asphyxiation
• Venom has evolved primarily to disable prey, self-defense is a secondary use