Why Do Reptiles Have Scales?
Scales are an important adaptation that evolved to help reptiles deal with the challenges of their environments. Most reptiles evolved scales for protection and to prevent dehydration, but there are also a number of novel uses too. There is no single explanation for the utility of scales.
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Scales
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A scale is the part of a reptile's skin that provides protection. According to Bellarmine University, the outer layer of skin is made up of thick keratine-filled cornified cells. This is true for most reptiles. However, there a few exceptions such as the shell of turtles, the skin of crocodiles and the underside of some snakes. They have scutes, which The Free Dictionary defines as a bony external plate.
Desiccation
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One advantage reptiles have over amphibians is that their scales prevent desiccation, which means to dry out. Amphibians must remain in water or very humid areas. Reptiles, on the other hand, are in much less danger of drying out, and they are so well suited for land that most don't need to return to the water in any appreciable sense during their lifetimes.
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Protection
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Reptile scales feel tough and horny, which helps to prevent abrasions and provide sturdiness and support. The scute-filled shell of a turtle in particular is so tough that it acts as a protective device, impervious to many predators. The crocodile, too, has a form of protective dermal armor.
Other Uses
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Snakes utilize scales to help them in the act of locomotion and, in the case of rattlesnakes, to make a rattling sound that warns off predators and animals that mean the snake harm. It is also believed that snakes grow every time they shed their skin.
Evolution
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Reptiles evolved over 300 million years ago from early amphibians called reptilomorphs. However, skin is composed of soft tissue that almost never fossilizes, so it is difficult to say when the reptile scales evolved. It most likely evolved parallel with the reptiles themselves, as it was an important development toward the increased dependency to land.
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References
- Photo Credit Lizard image by David G from Fotolia.com
