Turtle Classification

The classification of turtles is based on their bone structure, in which the constitution of the skull is predominant.
The most comprehensive classifications are those of Boulenger and Gadow, which are based on two groups. The first group (Ateco) includes specimens whose shell is made up of numerous small bony elements, irregularly arranged, and whose limbs are shaped like flippers, adapted to their aquatic life. The second group (Tecóforas) includes all the others.

Ateco Turtles

The group of ateco turtles comprises a single family, the sphargids, which in turn refers to a single genus with only one species of sea turtle. This species is distinguished by not having a retractable neck and by having the dorsal shield and plastron covered by leathery skin. It is known as the leatherback turtle (Dermochelys coriacea), named for its carapace and the five longitudinal ridges it has, which give it the appearance of that instrument.

It is one of the largest turtles living today. Specimens have been seen with a length of no less than 1.80 meters, but others have been reported at about 2 meters, weighing more than half a ton. The leatherback is found in the Atlantic, Indian, and Pacific Oceans, and occasionally in other seas, although it is always rare.

Tecóforo Turtles

Tecóforos are distinguished by having vertebrae joined to the ribs, forming bony expansions that create a true shield, covered by horny plates.

One of the characteristic details is that, if the neck is retractable, it enters the space between the carapace and plastron, folding in a vertical S-shaped plane. In addition, their entire shell is covered with horny plates.

The Chelydrids

The chelydrids are a family of turtles with long tails, small plastrons, a very narrow bridge connecting the plastron to the carapace, and a very hooked snout or beak. They are American. They are divided into two genera, each with a single species.

One of them is the marsh turtle, which is found in slow-moving rivers and swamps, from southern Canada to Central America. Mainly in muddy-bottomed waters and even in stagnant, foul-smelling ponds.

The snapping turtle (Chelydra serpentina), which can reach up to 1 m from the tip of the beak to the end of the tail. It is very voracious and feeds on fish and amphibians, preferring deep waters. Sometimes it can be seen floating, carried by the current, with only the tip of its snout or beak above water, and quickly submerging at the slightest alarm. It is often found out of the water, and then its movements are slow, similar to those of crocodiles. The name snapping turtle has been given to it because of its aggressive instinct, which is observed even in newborn specimens. During the summer, it lays 20 eggs, which are edible. In captivity, it refuses all food. Its neck and limbs are so robust that they cannot be fully withdrawn into the shell.

Very closely related to this species is the alligator snapping turtle (Macroclemmys temmincki), native to the Mississippi and Missouri river basins.

The Kinosternids and Plastisternids

Kinosternids are found in North and Central America. They belong to the genus Kinosternum. The most interesting are the stinkpot turtle (Kinosternum odoratum) and the box turtle (Kinosternum leucostomum).

The stinkpot turtle is so called because of the foul odor of the secretion from its inguinal glands. Due to the arrangement of the shell, the box turtle...

The Pennsylvania box turtle (Kinosternum pennsylvanicum), very abundant in the southeastern United States and very voracious. Its meat is not edible, and it is a good swimmer and cunning when hunting its prey. It often swallows fishermen's hooks, who believe they have caught a large fish. During winter, it hides among moss and does not resume activity until spring arrives.

Testudinids

The family of testudinids includes the largest number and the main living turtles in the classification. They have a retractable neck and the shell is always completely covered with horny plates. It includes genera with terrestrial, amphibious, or aquatic species, distributed in almost all countries except Australia and New Guinea.

The genus Pseudemys includes some American freshwater turtles, with flat shells, short tails, and limbs with webbed toes, whose species are found throughout the Americas.

The painted turtle (Pseudemys scripta), found in New York State and Long Island, has a smooth, flat, and depressed carapace, dark olive or dark brown in color, with broad yellowish stripes on the front part of the neural and costal plates, while the marginal plates are reddish and the plastron is yellow.
It gives us details of its growth, explaining that during the first six or seven years of life, painted turtles grow regularly, as can be seen by the successive layers of the horny plates. But after this stage, due to a fusion process, the epidermis becomes smooth, and it is more difficult to determine their age.
The size of adult individuals is 16 cm in carapace length by 11 cm in width.

In Central America, there is a related species: the ornate box turtle (Pseudemys ornata).
The genus Clemmys includes seven or eight species of marsh turtles, which have the carapace and plastron rigidly joined, toes with webbed membranes, and a long tail without a terminal claw, longer in young specimens than in adults.

Among its species is the European pond turtle (Clemmys caspica), so named because of the appearance it presents when its plates and even its bones become gangrenous,