Turtles are diapsids of the order Testudines (or Chelonii) characterized by a special bony or cartilaginous shell developed from their ribs and acting as a shield. "Turtle" may refer to the order as a whole (American English) or to fresh-water and sea-dwelling testudines (British English). The order Testudines includes both extant (living) and extinct species. The earliest known members of this group date from 220 million years ago, making turtles one of the oldest reptile groups and a more ancient group than snakes or crocodilians. Of the 356 known species alive today, some are highly endangered.
Turtles are ectotherms—animals commonly called cold-blooded—meaning that their internal temperature varies according to the ambient environment. However, because of their high metabolic rate, leatherback sea turtles have a body temperature that is noticeably higher than that of the surrounding water. Turtles are classified as amniotes, along with other reptiles, birds, and mammals. Like other amniotes, turtles breathe air and do not lay eggs underwater, although many species live in or around water.
The study of turtles is called cheloniology, after the Greek word for turtle. It is also sometimes called testudinology, after the Latin name for turtles.
The hawksbill sea turtle
) is a critically endangered sea turtle
belonging to the family Cheloniidae
. It is the only species
in its genus
. The species has a worldwide distribution, with Atlantic
and Pacific subspecies
. E. imbricata imbricata
is the Atlantic subspecies, while E. imbricata bissa
is found in the Indo-Pacific region.
The hawksbill's appearance is similar to that of other marine turtles. It has a generally flattened body shape, a protective carapace, and flipper-like arms, adapted for swimming in the open ocean. E. imbricata is easily distinguished from other sea turtles by its sharp, curving beak with prominent tomium, and the saw-like appearance of its shell margins. Hawksbill shells slightly change colors, depending on water temperature. While this turtle lives part of its life in the open ocean, it spends more time in shallow lagoons and coral reefs.
Human fishing practices threaten E. imbricata populations with extinction. The World Conservation Union classifies the Hawksbill as critically endangered.
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Did you know?
- ... that the extinct sea turtle Psephophorus was once mistaken as an ancient armadillo due to the specimen's poor condition?