|MadSci Network: Zoology|
Thanks for your question about skin shedding, which biologists also call "moulting", in reptiles. There are four major groups of reptiles alive today: snakes, lizards, crocodiles and turtles. Snakes shed their skin all in one piece, turning it inside out as they do so, so that the shed skin forms a tube. Lizards also shed their skins but tend to do so in small patches, often starting with a split down the back. Some legless lizards shed their skins all in one piece but without turning it inside out and also with a split down the back so that the shed skin forms a sheet rather than a tube.
Crocodile skin is covered with large scales which are shed individually rather than all at once as in snakes, or in patches as in lizards. Due to their shells most turtles don't really shed their skins either. Instead, new layers are added to the undersides of their shells. The number of these layers can be used to determine the turtle's age. Some turtles shed the outer layers of their shells leaving them vividly bright and colourful. The skin on the parts of the body not covered by the shell is shed in patches as in lizards. Some soft-shelled turtles shed the skin on the whole of their bodies like this.
In addition to the living reptiles, there are of course a number of extinct groups, the most famous being the dinosaurs. It is interesting to speculate as to how the dinosaurs shed their skins. I don't know the answer to this, and I'm not sure anyone does, but I suspect that since shedding the skin all in one piece seems to be confined to legless reptiles, the smaller dinosaurs probably shed their skins in pieces like lizards and the larger ones may have shed their scales individually like crocodiles.
Since reptiles are popular pets there are quite a few web sites about this subject. Here is a link to one of them. You can find lots others can by using a search engine such as Google.
Try the links in the MadSci Library for more information on Zoology.