Skeletal Structure of Reptiles
The morphology of reptiles is incredibly diverse. Reptiles branched out quickly when they first evolved and produced varied creatures such as turtles, snakes and dinosaurs. Reptile skeletons are equally varied.
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Skull
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The first reptiles to evolve 300 million years ago were called anapsids. They had no temporal fenestra--a large hole in the back of the skull. It is believed that turtles are surviving anapsids, although it is also possible that they re-evolved this skull configuration over time. Later reptiles diverged into two groups. Synapsids include extant mammals and mammal-like reptiles. They have a single temporal fenestra. Diapsids include all other true reptiles. They have two temporal fenestra, which impart room for jaw muscles and a more powerful bite.
Adaptations
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Reptiles are better adapted to deal with the rigor of living on land than their amphibian ancestors. They have more compact bones in the feet and a highly flexible backbone. Another feature that differs from amphibians is that modern reptiles have several vertebrae connected to the upper bones of the pelvis, which afford reptiles an expanded connection between hind limbs and skeleton. Amphibians only have one connected vertebra. Early reptiles had two.
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Sturdiness
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According to the book "The Age of Reptiles" by Edwin Harris Colbert, reptiles have a well defined articulation between the bones and a more efficient skeletal structure, which both give reptiles a somewhat more sturdy skeleton. This is also apparent in the skull because it strongly protects the brain and offers a base for the operation of the jaw.
Turtles
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The turtle has some of the most interesting skeletal modifications of any reptile. Its vertebral column and ribs are fused to the bones on the inside of the upper shell. The vertebrae of the neck and tail are small enough to allow great flexibility so that most turtles can pull back into the shell. The forelimbs are connected to the bottom of the shell by a pectoral girdle that extends down the length of the turtle from the vertebral column.
Snakes
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The skeletal structure of the snake is unique . The website Pet Education states that the snake's ribs are attached to all vertebrae--which total between 130 to 500--except those in the tail. Some boas and pythons retain a vestigial pelvis utilized for reproduction. The bones in the skull are connected to elastic ligaments, and the joints of the jaw are double hinged and positioned in the posterior, so the snake can stretch its mouth wide and "walk" the prey back into its mouth. Teeth point backwards; two rows are on each upper jaw, and one row is on each lower jaw. Hollow, grooved fangs can inject venom.
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References
- Photo Credit the skull of the giant reptile image by Natalia Pavlova from Fotolia.com
