What are the characteristics of turtles, tortoises, and terrapins?

The term terrapin is applied to turtles found in freshwater and brackish water that are considered excellent
eating.
Turtles and tortoises have short, thick bodies encased in shells. All turtles and tortoises have limbs that
enable them to walk on land. This group of reptiles has modified limbs that enable them to swim as well as
to walk on land. Some turtles and tortoises spend most of their time in the water; their limbs are primarily
adapted for swimming, and they move about on land with creeping and crawling motions. Turtles and tortoises
do not molt their thick epidermal skin. A new epidermal scale forms beneath the old one as they grow.
This allows for growth of the animal. These epidermal scales, or scutes, form rings that can be used to estimate
the animal's age. However, this method may give an inaccurate indication because more rings may form during
a good year. The hard, tough layer of scales prevents moisture from dissipating from the body. In turtles and
tortoises, this horny epidermal layer forms an exoskeleton, which has two parts. The upper part is called the
carapace and also forms a part of the vertebrata and ribs of the animal. The lower portion is called the plastron.
Turtles and tortoises do not have teeth. Their jaws form very sharp or crushing plates, depending on the
diet of the animal. The front part of the jaws forms a horny beak.