Reptile+Anatomy

For the shift from aquatic to terrestrial animals, the vertebral column needed to be strenghtened to support the additional gravitational weight. At the same time limbs were being developed. The new functions required a more tightly linked spinal column, a modified skull, and elaborated limbs.

=﻿Scales, Glands, and Skin Structure:=

Crocodiles, turtles, and some lizards have bony plates that are underneath the dermis. They are called Osteoderms or Osteoscutes. The structure of of the Osteo-derm/scutes matches that of the dermis. The outer most layer of bone is spongy and porous, with the inner layer dense. The Osteo-derm/scutes are usually on the back or sides of the animal and are loosely attached to each other in rows and collumns. This allows for flexibility and at the same time maintains the protectiveness of bony armor. Reptiles have many different skin glands all over the body, most are inconspicuous and are multicellular. Most of the glands secrete substances that are liquid and wax based. These are used for pheromones, waterproofing, and surfactant.


 * Order Squamata: **

**__Lizards: __** Lizards shed their skin in patches **Tongue ** Some lizards have long, black, forked tongues used for examining objects that they come across. Others have a blunt, fleshy tongue with a nick at the end used for picking up prey and investigating objects. Some have a viscous tongue used lap up prey. Some have an extremely tongue long tongue that is sticky at the tip and used to catch prey from a distance. **Teeth ** There are two different forms of teeth, //acrodont// and //pleurodont//. //Acrodont// lizards have their teeth set in the edges of their jaws and there are no defined alveoli (sockets) or a longitudinal socket groove. //Pleurodont// lizards have the teeth set in a deeply-cleft, longitudinal socket. **Tail ** A lizard's can be up to four or five times the rest of its body length. Some lizards also have the ability to snap off their tail to distract predators and then escape. **Changes in Color ** Some lizards can change color. The color of a lizard can be effected by; light, temperature, and the health of the lizard.
 * Skin **

__ Snakes: __

Sense Organs Snakes have very unique sense organs. Snakes mostly use their sense of touch and smell. They have no eyelids, but transparent caps, called brille, to protect their eyes. Because of this, they have limited eye movement. Instead of an external ear, middle ear, or tympanic membrane (eardrum) snakes have a small ossicle (ear bone), called columella. The columella is used to detect vibrations of sound waves conducted through the ground. Though they can pick up some sound waves through the air they only do so at very low frequencies. Snakes also sense smells differently than other animals. Snakes do not use nostrils or nasal cavities to smell. They flick their tongue in and out to smell. Snakes have a small organ on the roof of their mouth called the vomeronasal organ, or Jacobson's organ. Snake use their forked tongue to bring air particles to the vomeronasal organ. The snake then identifies the smell as prey, predator, or otherwise. Vipers, rattlesnakes, and other members of the family of snakes known as the 'pit vipers' have special pits located between their eyes and nostrils. They use these pits to sense minute temperature changes. This is used to help them find warm blooded prey. A pit has two chambers. The interior chamber is the internal temperature of the snake itself. The exterior chamber heats up when it is close to a heat source, and the snake is then able to detect the temperature difference between the two chambers. This system is so accurate that pit vipers are actually able to detect temperature changes as little as 0.002° Celsius. <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">**<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Integument **

<span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">**<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Musculature and Locomotion ** <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Snakes use their muscle to ingest their prey as for locomotion. Snakes move in four basic types of locomotion: <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">//__<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Serpentine or lateral progression: __//<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;"> This is what most people call “slithering”. All water snakes use this method and is allows a snake to reach its maximum speed. <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">//__<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Rectilinear: __//<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;"> This caterpillar or inchworm movement is used by large, heavy snakes to travel in a straight line. These snakes move the skin on their belly and then drag along the rest of their body. <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">//__<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Side winding: __//<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;"> This is when a snake throws its body in a sideways looping motion. It is used by snakes that live in deserts with loose sand. <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">//__<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Concertina: __//<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;"> This is used by some snakes while climbing trees. The snake’s body forms horizontal loops and then the head goes forward and the body follows. This is comparable to a spring. <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">**<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Skeleton and Teeth ** <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Since snakes have no appendages their skeletons are not very complex. Some snakes have vestigial structures similar to pelvic bones. This is rare and occurs in species like boas and pythons. Sometimes this will occur externally and is called spurs and they are used in reproduction. Other snakes only have a skull, vertebrae, and ribs. Snakes can have between 130-500 vertebrae, with ribs attached to each one; this does not include the bones in the tail section. Snakes have a very unique skull and teeth makeup. Snakes have certain adaptations in their skull which allows them to consume prey much larger than themselves. Their jawbones are connected with elastic ligaments, which let the snake stretch their jaw a lot. The joint that combines their upper and lower jaws is in the back of the head, allowing the mouth to open to its maximum. When swallowing larger prey a snake can move its jaw laterally because the lower jaw is not fused to the upper jaw. A snake also has a quadrate, a loosely attached bone, on each side of its mouth allowing a double hinge so as the snake swallows it moves its jaw laterally and walks the prey into its mouth. Backward curved teeth also make it easier for a snake to swallow prey. Because the teeth are angled towards the throat it prevents any live prey form wriggling loose. Snakes have two kinds of teeth, acrodont (attached to the bone) and polyphydont (able to grow back when lost). Snakes can and need to grow back teeth because they often loose several teeth during their lives while feeding. The type of teeth a snake has differs depending on the method used to capture and kill prey. There are three kinds of snake dentition: <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">//__<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Constrictor dentition: __//<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;"> Most snakes have a row of teeth on the upper and one on the lower jaw. All of these teeth are short and hook like and all non-poisonous snakes have this dentition. Poisonous snakes have either grooved fangs or hollow fangs. <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">//__<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Groove fanged: __//<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;"> Snakes with fangs only have teeth on their upper jaw, plus the fangs. The fangs have grooves for the venom to follow into the prey from venom glands on the top of their head. <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">//__<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Hollow fangs: __//<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;"> Hollow-fanged snakes have fangs that are more like hypodermic needles. These fangs are either fixed of erectile. Erectile teeth can be retracted into a groove in the mouth but fixed teeth are always extended. <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">**<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Respiratory System ** <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">An air sac, trachea (windpipe), lungs, and bronchi are all found in the respiratory system of a snake. A snake’s trachea starts in the back of the oral cavity at the glottis, and at its end it branches into two bronchi near the heart. The bronchus on the right goes into the right lung where it is elongated, while the left bronchus goes into the left lung where it is reduced or vestigial. The end of the lungs is vascular (with blood vessels) and functions in gas exchange, but the second half of the lung is an avascular (without blood vessels) air sac that extends into the tail region. In most snakes this air sake regulates pressure inside the body cavity in a hydrostatic function. Snakes air enters and leaves the lungs because of movement of the ribs and motion of body muscles, because snakes have no diaphragm. ||  ||   ||
 * < <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Snake scales protect from abrasions and from dehydration. The scales on a snakes belly are the largest while the scales on the top and sides of a snake are thinner and smaller. Those scales found on the bottom are scutes and they protect and support the tissue that touches the ground. You cannot tell a male snake from a female based on its color. Snake scales come in a large variety of colors and patterns. Snake skin is very dry, though most people describe it as shiny. Snakes have only two glands on their skin. They are a pair of anal scent glands. The substance that they secrete is used to mark territory, attract a mate, and protect them from predators. Snakes grow until they die by shedding their skin. The shedding of the skin is called ecdysis. A snake will obtain a bluish hue before it sheds, caused by fluid between the different layers of skin. Dysecdysis, abnormal shedding, is caused by parasites, trauma, and malnutrition. Snakes will normally shed all of their skin in one piece, this includes the brille. If a snake has a rattle then only that will not be shed. Rattles get an added segment after each growth period. Some people think that rattle segments represent the age of the snake, but since a snake can shed multiple times a year, this is not true. Since young snakes grow quickly they may shed as often as once every two months or so. A rattle snake may also lose some of the end segments of its rattle as it ages.

Digestive System

A snake’s digestive system has colon, stomach, small intestine, esophagus, and glands. The esophagus runs from the pharynx to the stomach, adjacent to the air sac. In a snake food is moved to the stomach by the movement of the entire body because the esophagus has very little muscle. The stomach isn’t very advanced, nor is the junction between the esophagus and stomach well defined. The stomach is short and filiform in shape with longitudinal folds to increase surface area for digestion. The small intestine is simple with a few loops or folds but is mostly a long tube that gets food from the stomach and transports it to the large intestine or colon. The colon caries the feces to the cloacae opening, where it is disposed. The cloaca receives products from the digestive, urinary, and reproductive systems. The gall bladder, pancreas, and liver are all a part of the digestive system. The liver is the largest internal organ in a snake’s body. It fills up the space between the stomach and heart. One of the livers main functions is to produce bile. The spleen and gall bladder are found at the posterior tip of the liver. The gall bladder stores the liver’s bile and releases it into the small intestine as needed. The pancreases will also secrete digestive enzymes and will produce hormone that regulate blood sugar.

Cardiovascular System

A snake has a three chambered heart made up of two atria and one ventricle. The left and right atria receive blood from the lungs and body and pass it to the ventricle to be circulated again. The heart is encased in a sac called the pericardium and is located at the bifurcation of the bronchi. Due to lack of diaphragm the heart is able to move around. This adjustment protects the heart from damage while large prey is passed through the esophagus. The spleen is attached to both the pancreas and gall bladder and filters the blood and recycles old blood cell. The thymus gland is above the heart and in fatty tissue and is responsible for the maturation of special immune cells in the blood.

Endocrine System

The glands that secrete hormones essential to normal body function are the endocrine glands. A snake’s thyroid gland is in the throat and regulates growth and development, like shedding. The parathyroid is paired and located near the thyroid and maintains the metabolism of calcium. Both of the adrenal glands are in the tail region and are in a mesentery (membrane sheet attaching organs to the body wall) near the reproductive organs. They secrete adrenaline when the snake is in dangerous situations.

Genitourinary System

The kidney is responsible for urinary output. A snake’s kidneys are elongated, with the right nearer to the head than the left. They filter blood and remove waste products. The waste is transported via the ureters, which are the hollow tubes that transport urine. Since snakes have no urinary bladder the urine is empty directly into the cloaca as opposed to being stored. The paired gonads, testes in the male and ovaries in the female, are situated with the right being closer to the head than the left. The gonads are nearer to the head than the kidneys are. Female snakes have the ovaries near the oviducts which will carry the eggs to the uterus before they enter the cloaca. Some snakes are oviparous (egg-laying) and some are viviparous (having live birth). Snakes have no epidiymides so the sperm are transported from the teste through the ductus deferens to the cloaca. The male has organs called hemipenes that are posterior to the cloacal opening. They are paired copulatory organs and only one is used at a time to transfer sperm. The hemipenes are located near the musk glands, which females also have

**<span style="font-family: 'Times New Roman','serif'; font-size: 16pt; line-height: 115%;">Order Chelonia: **<span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;"> Tortoises and Turtles Turtles shells grow constantly and are shed in flakes and sheets continuously.

<span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">**<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Parts of a shell: **<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;"> There are two parts to the shell of a turtle: the upper portion is called the "carapace" and the bottom half is called the "plastron." Both shells are actually made of many fused bones. The carapace is the fusion of about 50 bones - the ribs and vertebrae. The plastron is the fusion of bones including the clavicles (collar bones), bones between the clavicles, and portions of the ribs. A bony bridge joins the carapace and the plastron along the side of the turtle. Some turtles have a moveable joint, usually in the plastron, which acts as a "hinge" and allows the turtle to pull the carapace and plastron together tightly, while the turtle retracts its body into the shell. Shells have a blood and nerve supply, so bleeding and pain can result if the shell is injured. <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">**<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Scutes on the Carapace ** <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">**<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Scutes: **<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;"> The shells are covered with a layer of keratin (the same type of material that makes up our fingernails or horses' hooves). The keratin is arranged in patches called scutes, or shields. The carapace usually has 38 scutes, and the plastron, twelve to fourteen. The names and numbers of the scutes roughly correspond to the adjacent bones and body portions. The scutes, however, do not precisely overlap the bones. Instead, they are staggered, which helps give the shell more rigidity. <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">**<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Scutes on the Plastron ** <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Some aquatic turtles, such as soft-shelled and sea turtles may have fewer bones in their carapaces, and the scutes are replaced by leathery skin. <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">**<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Scute patterns: **<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;"> Different species of turtles have scutes of different patterns and designs, and there are often individual differences among members of the same species. <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">**<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Shell shapes: **<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;"> The shell shapes of turtles differ with each species, and are often related to habitat. Most aquatic turtles are generally flatter, allowing them to move faster through the water. Tortoises, on the other hand, have carapaces that are dome-shaped. <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">**<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Shell Growth: **<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">As a shell grows, the number of scutes generally does not change, but their size does. In some turtles, old scutes are shed and replaced by larger, new ones. In other species, including box turtles, tortoises, and wood turtles, scutes enlarge in diameter as new keratin is laid down. The "growth rings" in scutes have been used be some experts to help determine the age of a turtle. Age estimation based on growth layers, however, can be erroneous for several reasons:
 * <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-list: l0 level1 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; tab-stops: list .5in;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Some turtles produce multiple growth zones per year.
 * <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-list: l0 level1 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; tab-stops: list .5in;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Growth is determined by changes in the environment (seasons), so age determination by examination of growth rings would be more accurate in wild turtles, than those kept in environments, which do not change significantly.
 * <span style="display: block; line-height: normal; margin: 0in 0in 10pt; mso-list: l0 level1 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; tab-stops: list .5in;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Growth layers may wear with age, so older turtles may be estimated to be younger than they really are.



<span style="display: block; font-family: 'Times New Roman','serif'; font-size: 16pt; line-height: 115%;">Order Crocodilia: <span style="display: block; font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">Crocodiles, Alligators, Caimans, and Gavials. Crocodylians shells grow constantly and are shed in flakes and sheets continuously. Crocodiles have features that are advanced and peculiar to their order. they have a four chambered heart. The mouth and the nostrils are separated by a hard plate. They have more well developed lungs compared to snakes. They have the highest developed brain of any reptile. Order Crocodilia has no Jacobson's organ. They have well developed digestive systems but no bladder. They must pass urine in the cloaca with solid waste.

Mouth: To achieve its characteristic gape, the alligator does not merely drop its lower jaw but raises its head and upper jaw. The teeth are used for seizing and holding prey. Teeth are not for chewing. Stomach: Because an alligator cannot chew, its stomach has two parts, which are a muscular gizzard and a digestive section. The gizzard's grinding of food is aided by swallowing hard objects. Heart: Blood passes from the right ventricle through the pulmonary artery for oxygenation by the lungs; it returns through the left atrium to left ventricle, and is pumped out to the body. Scales: The alligator's armour is composed of horny scales, each developing on it's own and replaced by layers from below. Those shielding the back and tail have bony plates beneath them

**<span style="font-family: 'Times New Roman','serif'; font-size: 16pt; line-height: 115%;">Order Rhynchocephalia: **<span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;"> Tuatara, often called a living fossil, is the only living member. Extinct members were the Saurischians (Tyrannosaurus and other "reptile-hipped" bipedal carnivores), from which birds arose. Tuatars are lizard like and have stoute bodies, large heads, and thick tails. Their upper jaw is chisel-beaked and overhangs the lower jaw. Tuataras have a series of erect spines on their neck and back. Tuataras lack a tympanum.

<span style="display: block; font-family: 'Times New Roman','serif'; font-size: 18pt; line-height: 115%; text-align: center;">References <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">[] <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">[] <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">[] <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">[] []=

Second Edition Herpetology An intorductory Biology of Amphibians and Reptiles