There are approx 294 species of chelonians alive today. They all share a
basic appearance, with a hard shell made up of scutes (hard, bony skin) that
can be described as either a hard or soft shell. This shell consists of two
parts: the top dorsal carapace and the plastron (the part that protects the
belly). Chelonians are a well-known group and can be found in ponds,
streams, lakes, and oceans. Several species are endangered. There are three
main groups of chelonians: turtles (medium-sized freshwater chelonians and
large saltwater chelonians), tortoises (large land dwelling chelonians
sometimes found in the desert), and terrapins (small turtles, in North
America considered to be one species with hollow plates on the carapace,
and in Great Britain considered to be a number of species of pond turtles).
There are 11 families:
Chelydridae (snapping turtles, alligator snapping turtles) 3 spp
Emydidae (pond turtles, box turtles, terrapins) 111 spp
Testudinidae (tortoises) 48 spp
Dermatemydidae (river turtles) 1 spp
Kinosternidae (mud turtles, musk turtles) 27 spp
Carettochelyidae (pignose turtles) 1 spp
Trionychidae (softshell turtles) 25 spp
Cheloniidae (sea turtles) 6 spp
Dermochelyidae (leatherback turtles) 1 spp
Pelomedusidae (Afro-American sidenecked turtles) 23 spp
Chelidae (Austro-American sidenecked turtles) 48 spp
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