Snakes and Evolution
September 4, 2013
BIO/101

Snakes are reptiles that have been on Earth for over millions of years. Snakes are a peculiar creature because the true origin of snakes is unknown. The delicacy of their structure allows for error in fossil records, because many of the first fossil records of snakes are incomplete skeletons. A fact known to be true is that snakes were legged vertebrates. The structure of a snake may be complex, but it is suited for survival. This fact changes factors such as food, shelter and survival, thus the evolution of snakes. Fossil records of snakes date back to the crustaceous period. This era signified the end of dinosaurs but there is evidence of snake life in this era. An interesting fact is that dinosaurs are descendants of cotylosaurs which then produced Diapsids, so snakes are not direct descendants of the dinosaur, but they are evolutionary cousins of Tyrannosaurus and Triceratops. During this era all the continents were together as one, and they were called Pangea. The shuffle of all the continents caused snakes to adapt to the new environmental changes, and strive to survive through natural selection. According to the Bible, snakes were forced to give up their legs and slither on their belly because of mischievous doings. This may be a story or fact but fact is that snakes had legs at one point in time. The first records of legged snakes were found in the Middle Eastern. Another record of a snake was later found in South America, where this snake had two legs. These records presented three types of snakes proving to have had vestigial hind legs. This theory proves that the origin of snakes had legs. Pythons and other snakes still have spurs or ball joints close to the tip of their tail. The spurs or ball joints are commonly used for support when mating. The true origin of snakes is unknown however because of many similarities the snake is closely related to reptiles. Structure similarities to that of a snake and of a reptile stem from their skulls. The skulls have no temporal opening. Snakes are also similar to lizards because of features in the structure of their skull; both, for instance, possess a moveable quadrate bone at the back of the jaw, and both are missing the quadratojugal bone at the rear of the skull. Snakes can also lay eggs like many other reptiles however; some snakes can also have live births. The structure of a snake is perfect for the way it lives. Snakes do not possess external ears, so the ability to hear does aid a snake. Although a snake cannot hear, it can feel vibrations of moving objects or animals surrounding them. It has not been proven whether snakes evolved from land or sea, but because snakes do not have gills they can stay underwater for hours taking the oxygen from water it swallows. However, snakes cannot live in water because it will need oxygen from the air to survive. Most snakes that burrow underground are usually blind due to the dirt and sediment. As in any creature a snake sheds its old, dead skin to allow them to grow and rid themselves of parasites. In the days leading to shedding snakes are very vulnerable. Excess fluid between the old skin and new skin causes a discoloration in the eyes, temporarily blinding the snake. Once the process of shedding has begun a snake will hide to protect itself during this vulnerable time. The last process of evolution concerning a snake is its diet. Snakes vary size therefore their dietary needs are different. Snakes are carnivorous creatures with diets ranging from common pests to birds. Snakes that live in trees find their prey on the tree tops. As seen on the diagram the structure of a snakes’ tongue is pronged. This two pronged tongue dissolves air molecules. This statement suggests that snakes can taste their prey through the air. This process allows a snake to know when prey is around. The jaw of a snake is expandable allowing a snake to swallow food that is larger than its body. Although many snakes have venom in their fangs or saliva, snakes do not use this venom on their prey. The venom is simply a form of protection against other predators. Although snakes may be one of the oldest residents of Earth, residing on Earth when all the continents were together, and called Pangea. Scientists and paleontologist still have lots to discover about snakes. It is still unknown if whether snakes derived from land or sea, but one thing for sure is that they had legs. These legs may have been vestigial or not but over time they became useless. The structure of a snake goes through various changes such as the shedding of skin, the variants in child birth. No matter what the thought of a snake is, the structure of a snake allowed it to survive natural selection and adapt well to new environment. Thus there are still snakes on Earth million years later.

References
Flank, L. Evolution of Snakes retrieved from: http://arachnophiliac.info/burrow/evolution_of_snakes.htm

Strauss, B. Prehistoric Snakes - The Story of Snake Evolution retrieved from:

http://dinosaurs.about.com/od/otherprehistoriclife/a/Prehistoric-Snakes-The-Story-Of-Snake-Evolution.htm

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