The Chelonian's shell, which is made up of about 50 different bones, actually is an evolutionary modification of the rib cage and part of the vertebral column.
The shell itself actually has two parts: an upper section, the carapace, and a lower portion called the pastron, which are joined by a bony bridge. Some turtles have a moveable joint, usually in the plastron, that acts as a hinge and enables the creature to pull the two shell sections together tightly while it retracts its body inside. Shells have nerves embedded in them and a blood supply as well, so if a turtle shell is injured, it may bleed and feel pain.
9. Tortoises Orbited the Moon Before Astronauts In September 1968, the Soviet Union launched the space probe Zond 5 on a mission to orbit the moon and test conditions as a prelude to a possible lunar mission by cosmonauts. Along with a life-size human mannequin equipped with radiation detectors, the spacecraft carried a number of living passengers, including a pair of Russian tortoises. After a week in space, Zond 5 returned to Earth and successfully splashed down in the Indian Ocean.
8. Alligator Snapping Turtles Lure Prey With Their Tongues One of the most fearsome Chelonians around is the alligator snapping turtle, Macroclemys temminckii, which is the biggest freshwater turtle in North America. It can grow to 2.5 feet long, can weigh as much as 200 pounds, and has powerful jaws, a sharply-hooked beak, nasty bearlike claws and a muscular tail. The alligator snapping turtle does eat some aquatic plants, but it's mostly a carnivore that dines on a variety of smaller creatures -- fish, frogs, snakes, worms, clams, crayfish and even other turtles.
The alligator snapping turtle catches prey by way of a fiendishly clever evolutionary adaptation: an appendage to its tongue that, when wriggled, looks like a worm. Fooled fish will swim right into range of the hungry predator's jaws.
7. They Make Sounds, Even Though They Lack Vocal CordsChelonians can make sounds by swallowing or by forcing air out of their lungs, and some species emit unique noises. The red-footed tortoise, a South American species, makes a series of clucks that sound like a chicken. Male Travancore tortoises in Southeast Asia emit a high-pitched whine that sounds like an electric motor when mating. The giant musk turtle found in Central America, is known for yelping like a dog when it is startled or being attacked.
But the weirdest sound is made by nesting female leatherback sea turtles (Dermochelys coriacea), who make a distinctly unladylike noise that resembles a human belch.
6. Males Select Potential Mates By Sniffing Tails
Male chelonians' method of sniffing under other female chelonians' tails is relatively sensible, not to mention functional. Since both males and females' sexual organs are hidden inside their cloaca, a cavity used for both reproduction and eliminating waste, humans have trouble telling by sight the sex of a turtle.
Turtles and tortoises, however, possess an extremely keen sense of smell. Males apparently can detect the scent of pheromones, a type of identifying chemical, that is secreted inside a female's cloaca.
5. They Don't Have Ears, But Can Perceive Low-Pitched Sounds
It's true that chelonians can't hear anywhere near as well as humans because they lack an ear opening, but they can detect certain types of sounds. Scientists have found that their middle ears have a very thick eardrum-like membrane, which limits the frequency range they can perceive. But that adaptation is extremely efficient for bone-conduction hearing at low frequencies, according to Behavior of Exotic Pets.
Our hard-shelled friends also can't differentiate loudness as well as we can. The spotted turtle, Clemmys guttata, for example, has a peak sensitivity of just 4 dB, compared to 120 dB in humans. Fortunately, their sense of hearing is good enough to detect the presence of predators.
4. Turtles Are Nearly As Old As The Dinosaurs
Amazingly, some turtles that existed in the age of the dinosaurs are still around. Pelomedusidae, a family of freshwater turtles native to eastern and southern Africa, first appeared about 120 million years ago. The first tortoises emerged on land at the start of the Tertiary Period 65 million years ago, shortly after the dinosaurs died out in a mass extinction. In the ocean, the oldest surviving species of sea turtles, the Cheloniidae, date back 55 million years, according to the book Turtles of the World.
3. Turtles Breathe Without A DiaphragmMost air-breathing vertebrates draw air in and out of their lungs using a diaphragm, a muscle that contracts and relaxes with each breath to expand the ribs. But turtles don't have a diaphragm, since the rigidity of their shells would prevent their ribs, which are connected to them, from expanding. Instead, turtles must move their limbs or neck, and utilize other muscles connected to the pleural cavity (the area around the lungs), to help them breathe.
2. They Have Favorite Colors
Our shell-wearing reptilians are visually-oriented creatures and rely on sight to identify other members of the same species, food, and potential danger, such as predators. Sea turtles, for example, are so dependent on sight that when researchers blindfolded some of them,
the animals were unable to find their way back into the water.
Research also shows that turtles not only can perceive colors, but that certain colors -- red, orange and yellow -- seem to be the most appetizing to them. When they see an object in one of those shades, they display "investigative behavior," which suggests that they're checking it out to see if they want to eat it.
1. There's A Turtle That Seems Part Skunk
The African helmeted turtle, Pelomedusa subrufa, is the most widespread turtle species in Africa, found just about everywhere south of the Sahara desert. It's a hunter-scavenger that hunts in packs and seems happy to eat most anything, from parasites lodged in the skin of rhinoceroses to young birds and small mammals. The helmeted turtle's reputation is also odorous as well. It smells really, really awful. That aroma comes from four glands, one under each leg, which release a foul-smelling liquid seems to repulse horses as well as humans.