Terrapins or water tortoises are a group of several species of aquatic reptile of the order Testudines living primarily in fresh or brackish tidal waters, but have the clawed feet of tortoises and not flippers of marine turtles. In American English, they are referred to as marsh, pond, or tide-water turtles, with some species called pond sliders as well. Whereas tortoises are almost strict herbivores and frugivores — largely feeding on flowers, grasses, leaves, and fallen fruit — a great many terrapins are mainly carnivorous — largely feeding on amphibians, arthropods, freshwater fish, and molluscs — though some are herbivores. Terrapins are identified primarily with the taxonomic family Emydidae, but do not form a single taxon and may not be closely related, with some belonging to the families Geoemydidae, Pelomedusidae, Podocnemididae, and Chelydridae. Though primarily aquatic, terrapins do relatively frequently come to land for many reasons, but particularly to warm up by basking in the sun.
Terrapin in the context of Turtle
Turtles (order Testudines) are reptiles characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked turtles), which differ in the way the head retracts. There are 360 living and recently extinct species of turtles, including land-dwelling tortoises and freshwater terrapins. They are found on most continents, some islands and, in the case of sea turtles, much of the ocean. Like other amniotes (reptiles, birds, and mammals) they breathe air and do not lay eggs underwater, although many species live in or around water.
Turtle shells are made mostly of bone; the upper part is the domed carapace, while the underside is the flatter plastron or belly-plate. Its outer surface is covered in scales made of keratin, the material of hair, horns, and claws. The carapace bones develop from ribs that grow sideways and develop into broad flat plates that join up to cover the body. Turtles are ectotherms or "cold-blooded", meaning that their internal temperature varies with their direct environment. They are generally opportunistic omnivores and mainly feed on plants and animals with limited movement. Many turtles migrate short distances seasonally. Sea turtles are the only reptiles that migrate long distances to lay their eggs on a favored beach.
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