Lab 2: Turtle Diversity

Matt Knestrick & Megan Thornhill

Intro

This week in lab, we looked at the shells of turtles, as well as examined specimen of the 14 known turtle families.

Shells

The turtle shell has two main parts, the carapace (the top part) and the plastron (that part underneath the turtle’s body). Each part is composed of bones covered by thickened scales called scutes. The types of carapaces and plastrons vary among turtle families.

Turtle Families

The first three families, Chelidae, Pelomedusidae, and Podocnemidae, are in the broad clade of turtles called the Pleurodira. THis means that whent hese turtles seek to protect their head, they fold their neck along the side of their shell to draw their head in.

Chelidae are the Australoamerican Side-neck Turtle, tropical or sub-tropical aquatic turtles with flattened skulls and shells.

Pelomedusidae are the African Mud Terrapins. These turtles are relatively small, with domed shells, and large heads. They are primarily aquatic.

Family Podocnemidae are the Madagascan Big-Headed Turtles and American Side-Neck Turtles. They live in the Southern Hemisphere, and are fairly large river turtles. They have flat,stream-lined shells for speed in the water.

The rest of the turtle families are in the clade Cryptodira. These turtles have cavities inside their shells that they can pull their necks into, allowing them to pull their heads into their shells.

Chelydridae are the Snapping Turtles. They can be found in Ohio, one species of which is the common snapping turtle, or Chelydra serpentina. Snapping turtles have large heads, flat carapaces, and a much reduced plastron. They are primarily aquatic.

Family Cheloniidae are he Hard-shelled Sea Turtles. They are almost entirely aquatic, with flipper like appendages, and appearing only on land to lay eggs on beaches.

Dermochelyidae are the Leatherback Sea turtles. They are some of the largest turtles, and are almost entirely aquatic. Their shells lack scutes, giving them a leathery appearance, and they are “almost warm-blooded”: their unique skin retains heat generated by the muscles, somewhat similar to warm-blooded animals.

Family Carettochelyidae are Pig Nose Turtles. They are highly aquatic, with flipper like appendages, and a leathery shell (like the Leather Back Sea turtles). They are named for their pig-like nose with two prominent nostrils.

Trionychidae are the Softshell Turtles. There are two subgroups, one of which, Trionychinae, is found in Ohio. The two Ohio native species are Apalone spinifera and Apalone mutica. These turtles have flattened, leathery shells, and can respire cutaneously, or breathe through their skin.

Family Dermatemydidae are Mesoamerican River Turtles. They have domed, oblong shells, and small pointed heads with slender faces.

Family Kinosternidae are the Mud Turtles and Musk Turtles, and some species are found in Ohio. These turtles are among the smallest turtle species, and are sometimes called “stink pots”

because they can produce a musky odor.

Platysternidae are the Big-Headed Turtles, named because of their extremely large heads. They have large plastrons, flat shells, and very large tails.

Family Emydidae are commonly called Cooters, Sliders, or American Box Turtles. This family makes up the most abundant family of turtles in Ohio, with species such as Clemmys guttata, Emydoidea blandingii, and Pseudemys concinna. These turtles have large, hinged plastrons that allow them to totally enclose themselves within their shells.

Geomydidae are the Asian River Turtles, Lead & Roofed Turtles, or Asian Box Turtles. They are a very varied group, with a range of sizes from very small to very large, and some being totally terrestrial, while others are totally aquatic.

Testudinidae are the Tortoises. They are terrestrial, and typically have large, high-domed shells and elephantine like feet.