Class: Reptilia

From "repto" to creep. 7,000 species, 300 of which are in the US and Canada;

Characteristics of the class:

1. Tough, dry, scaly skin offering protection against drying and physical injury.

2. Shelled egg contains food and protective membranes for supporting embryonic develop[ment on land.

3. Jaws efficiently designed for applying crushing or gripping force to prey.

4. Some type of copulatory organ to permit internal fertilization.

5. Lungs better developed than amphibians and they suck air into their lungs.

6. Advanced nervous system - cerebrum large in relation to the rest of the brain.

Snakes:

If you happen upon a snake, how can you tell if it is venomous or not? Venomous snakes tend to have certain characteristics that distinguish them from non-venomous snakes. Knowing the difference can help determine if that snake your pet was "playing" with is venomous or not.

Pit Vipers

Members of the pit viper family, rattlesnakes, copperheads and water moccasins, have broad triangular heads. Non-venomous snakes have narrow rounded heads.

Pit vipers have elliptical shaped pupils. Non-venomous snakes typically have more rounded pupils.

Pit vipers have prominent curving fangs. Non-venomous snakes tend to have many small teeth.

Pit vipers have a deep pit located between the nostril and the eye, thus the term ""pit viper."" Non-venomous snakes do not have this pit.

Coral Snakes

Coral snakes are known for their distinctive color pattern of red, black and yellow. This pattern determines if the snake you are observing is a venomous coral snake or a harmless species.

Coral snakes have a yellow band on both sides of a red band and a black band between yellow bands. This means the color pattern is: yellow -- red -- yellow -- black -- yellow -- red, and so on. Non-venomous similarly colored snakes have the red band next to a black band.

A simple saying to help you remember is, ""red on yellow, kill a fellow. Red on black, venom lack.""

Ratsnake:

The Ratsnake is large and has the an extensive geographic range. Length: It reaches a maximum length of 8 '5, although such a specimen would be a true giant. Appearance: The Ratsnake is fairly variable in color and patten across its geographic range. Two basic pattern are present in adults: blotched and with four longitudinal stripes. Juveniles of this species are all fairly similar, having a blotched pattern with large, dark blotches present along the back and smaller, lateral botches on the sides. The head is often speckled with an irregular spear point pattern, and a dark band crosses the prefrontal scales. A post ocular stripe is usually present, as well. Northern and western juveniles tend to have larger, more prominent blotches, while in southeastern specimens, the blotches tend to be smaller and not as distinct from the ground color. Behavior: Some populations and subspecies of this snake have a reputation for being easily annoyed. Other individuals and populations are quite docile. Feeding: Being a large serpent, the Ratsnake is capable of eating quite large prey, up to the size of large fox squirrels. In many areas, this species is known for raiding chicken coops for eggs; hence the vernacular name of "Chicken Snake".

Coral Snakes. Here, in the United States, there are three main corals. The Arizona Coral Snake, the Eastern Coral Snake and the Texas Coral Snake). Appearance: All Corals in the United States have some variation of the color pattern black yellow red yellow black yellow red. Any other snake in the U.S. that has these colors, but not in that order are not venomous, therefore not a Coral Snake. Imitators: There are many milksnakes and the Scarlet Snake which mimic the colors of a Coral, but not the pattern, and color order. Behavior: Corals are strictly terrestrial snakes, burrowers at that. Venom: They have a HIGHLY neurotoxic venom. Drop for drop, a King Cobra's venom is less potent, in a subcutaneous bite. Corals don't hesitate to bite if they feel sufficiently threatened. Their first line of defense IS flight. They burrow into the substrate and can disappear out of sight and range VERY Quickly. If they are grabbed or held, they may or may not bite right away. If they do, they tend to hold on and chew. Their fangs are short , and though capable of piercing human flesh, require a bit of work to deliver their venom efficiently. Coral venom has been known to cause some pain and swelling at the bite site. The most notable effects are, of course, paralysis of the muscles in the lungs and heart. It is almost unheard of that anyone would die from a Coral Snake bite, since an effective Anti-venin has been developed. Interestingly, though. The first casualty of the Civil War was NOT a victim of combat, but the bite of an Eastern Coral Snake.

Cobra


Cobra, common name for certain members of a family of venomous snakes, known for their intimidating behavior and deadly bite. Cobras are recognized by the hoods that they flare when angry or disturbed; the hoods are created by the elongate ribs that extend the loose skin of the neck behind the cobras' heads. Location: These reptiles are found throughout the Philippines, southern Asia, and Africa.

The king cobra is the world's longest venomous snake. Size: It averages 12 ft in length but is known to grow to 18 ft. Appearance: It is olive or brown in color, with bronze eyes; some individuals are banded. Locations: It is found in the Philippines, Malaysia, southern China, Myanmar (formerly known as Burma), India, Thailand, and the Malay Peninsula. Feeding: It eats primarily other snakes.

The other cobra of Asia is known variously as the common, Asian, Indian, or spectacled cobra (due to the eyeglass-shaped pattern on its skin). It seldom reaches a length of more than 6 ft. The hood of the common cobra is, proportionately, much larger than that of the king cobra and is usually yellow to brown, with a black-and-white spectacle pattern on top and two black and white spots on the lower surface. Dangerous: This snake causes many deaths each year in India, where it is regarded with religious awe and is seldom killed. The common cobra is frequently used by snake charmers. It ranges from the eastern shore of the Caspian Sea to China and Malaysia.

Spitting cobra: Many species of cobras are natives of Africa. Among them is the spitting, or black-necked, cobra, found from southern Egypt to northern South Africa. This snake can spray its venom from a distance of about 8 ft into the eyes of its victims, causing temporary blindness and great pain. Varieties of the spitting cobra range in color from dull black to pink, the paler-colored ones marked by a black band around the neck. The ringhals, a different type of spitting cobra confined to southern Africa, is one of the smallest of the cobras, reaching only about 4 ft in length. It is dark brown or black with ridged, or keeled, scales and pale rings on the neck. The asp, or Egyptian cobra, is found along the northern coast of Africa.

Facts about the spitting cobra:

Name : Spitting Cobra - Hemachatus Haemachatus
Size : 1m , can be longer
Distribution : S.Africa
Habitat : Grasslands
Food : Birds , small mammals , frogs , reptiles
Breeding : Live-bearing with litters of up to 63 , but usually 20-30 young
Appearance : A thickset snake with keeled scales and a wide head . It is varied in color and may be marked with black bands on a grey , yellow or orange background , or it may be plain black or dark brown above , sometimes with paler speckles . It rears up and spreads a hood when alarmed .
Note : It can spray its venom accurately up to 8 feet , aiming at the face . That can cause blindness . Dangerously Venomous

The venom of cobras often contains a powerful neurotoxin and acts on the nervous system. With effective serum more available, however, the high death rate from cobra bites in some areas of Asia has decreased. Cobra venom has been used for many years in medical research because it has an enzyme, lecithinase, that dissolves cell walls as well as membranes surrounding viruses.

Boa


Boa, common name for nonpoisonous snakes of the boa family. Like all members of this group, boas are constrictors----that is, they kill their prey by squeezing it to death and then they swallow it whole. Boas use the coils of their body to suffocate their prey, rather than crushing it, as is commonly believed. They can stretch their jaws wide apart to swallow animals larger than their heads. Depending on the size of its prey, a boa may take several weeks or longer to digest its food. Many of the exceptionally large snakes of the world are of this family, but not all boas are large. Some are no more than 20 in. long when fully grown. Boas vary greatly in color and pattern.

Characteristics: The boa family contains about 8 genera and 39 species, characterized by vestigial hipbones and hind legs, which can be seen externally as a pair of movable spurs. Boas and pythons differ in several ways, primarily in the skeleton. Boas give birth to their young, while pythons lay eggs; pythons are confined mostly to Eurasia, whereas boas are found worldwide.

Probably the best-known boa is the boa constrictor, found in the jungles of Central and South America. Boa constrictors are usually yellowish or grayish, with a pattern of dark brown dorsal saddles; the tail is often reddish-orange. Size: Most adults do not exceed 6.6 to 10 ft. in length, although unusually large individuals may reach 13 ft. Stories of larger boas may have caused boa constrictors to be confused with anacondas (water boas) or with the pythons of Asia.

Tree boas, such as the brightly colored emerald tree boa, live in trees and have strong, prehensile tails. With their triangular heads, elliptical eye pupils, and long, curved front teeth, they resemble the venomous vipers.

Some smaller boas, such as the rubber boa, range throughout much of the northwestern United States. Found as far north as British Columbia, Washington, and Montana, the rubber boa, whose shiny brown skin resembles rubber, is a burrowing animal. Because of its blunt head and tail, it is sometimes called a two-headed snake.

Anaconda

Anaconda, common name for large South American snakes of the boa family. Anacondas are among the largest and most powerful snakes in the world. The common anaconda is the longest snake in the western hemisphere and the heaviest snake in the world; a large adult may be 20 ft. long and weigh 235 lb. Feeding: Anacondas kill their prey by constriction or squeezing. The common anaconda inhabits the river systems of northern and Amazonian South America east of the Andes. The yellow anaconda is much smaller, usually not exceeding 10 to 13 ft, and lives in the river systems of southern South America. Female anacondas give birth to living young.

Python (snake)

Python, common name for any member of a family of nonvenomous

snakes of the python family. Feeding: Many species of pythons are large and muscular and kill their prey by squeezing, or constricting, until the animal suffocates. Although most pythons feed on small mammals, some large species can kill and swallow small pigs and goats. They have rarely killed humans. Size: Pythons range from about 3 to 33 ft. long and weigh up to 300 lb. They have two tiny hind limbs, usually better developed in the male. Reproduction: The female lays 15 to 100 eggs, varying with size and species, and broods them until they hatch. Pythons are sometimes found in or near water.

Location: About 20 to 25 species of pythons exist, found in the tropical and subtropical regions of Africa, Asia, Australia, and the Pacific islands. The reticulated python of Southeast Asia is among the largest snakes, reaching a length of 33 ft. Other well-known pythons are the 25-ft. Indian python, a favorite of snake handlers.

Rattlesnakes

The rattlesnake is probably the most well known snake in North America. Locations: It is found all across the United States, usually in dry areas. The characteristic tip of its tail, consisting of a series of loosely connected horny segments that are vibrated as a warning signal, makes it easy to distinguish the rattlesnake from other snakes. Venom: The rattlesnake is poisonous and its bite can be very painful and sometimes fatal.

Rattlesnakes are pit vipers and, as such, have the ability to detect prey using heat-sensory organs located between each eye and nostril. Rattlesnakes are divided in two genera and more than 30 species are currently recognized. Types: Some of the most well-known species are timber rattlesnakes of the eastern and central United States, prairie rattlesnakes of the western states and the eastern and western diamondbacks the largest of the rattlesnakes.

The size and coloration of rattlesnakes vary from species to species

depending on the conditions in which they live. Some Mexican species are as small as 1 foot in length, while the eastern diamondback can become up to 8 foot long. Some species have transverse bands, but most have skin with dark diamond or hexagon shaped spots - usually gray or brown on a lighter background.

The diet of rattlesnakes consists of small animals (mostly small mammals such as mice, rats, squirrels and rabbits) that can be detected using their heat-sensitive organs. The prey is caught by striking rather than holding. The victim is bitten and venom injected through the two hollow fangs. Most small prey is immediately immobilized and soon swallowed whole by the rattlesnake.

Behavior: Most rattlesnake species are active during the day, but in hot climates they are often nocturnal. In the winter months they hide in crevices to hibernate. When the air gets warmer again they come out of hiding, often sunning themselves for several days just outside the entrance to their hiding place. Rattles: Each time the rattlesnake comes out of hibernation it sheds its skin and another section is added to the rattle on its tail. During the rapid growth in the first years, rattlesnakes may shed skin several times a year, and also the rattles may break off, so

the number of rattles is not an accurate measure of age. However, it is not unusual to find a rattlesnake with 10 or more rattles.

More about RattleSnake's Rattles

How rattles form: The rattle on the tail of rattlesnakes is formed from the successive remains of the scale covering the extreme tip of the tail . In most snakes , this scale is conical and the epidermis covering it comes away with the rest of the shed skin . In rattlesnakes , however , the terminal scale is shaped like an hour-glass , with a constriction somewhere around its center line . After the first shed , the skin around this terminal scale becomes thicker than normal . When the young snake sheds for the second time , this scale is torn away from the old skin , because it is held in place by the constriction . Now a new skin is formed around the tip of the tail but it shrinks away from the piece of old skin so that it is attached only loosely . When the snake sheds again , the second layer is prevented from coming away , the tail has two segments , one inside the other , and the cycle starts over again . Eventually a number of segments are built up , the oldest towards the end of the tail and the freshest towards its base . Each segment , then , represents a shed skin , but although the snake may shed four or more times each year , rattles that consist of more than six or seven segments are rare because the material is brittle and the tip , including the button , is usually broken off , leaving only the most recently formed rings .

Reproduction: All species give birth to live offspring that can manage on their own the instant they are born. They usually remain in the area where they were born for a week or so after which they disperse and begin to search for food.

Water moccasin

Called cottonmouth, highly venomous snake of the swamps and bayous of the S United States. Like the closely related copperhead, it is a pit viper and has a heat-sensitive organ for detecting warm-blooded prey. Reproduction: The young are born live. Appearance: The young snake is a pale reddish brown with transverse dark brown bands edged with white; as it ages the colors dull to a blotched olive or brown and then to an unmarked olive or blackish in old specimens. Size: The maximum length is 6 ft, the average from 3 to 4 ft . Behavior: A good climber, the water moccasin often relaxes on branches overhanging the water. If startled it erects its head and shows the white interior of its mouth-hence the name cottonmouth. It eats both warm-blooded and cold-blooded animals. It is aggressive in the wild state but may become quite tame in captivity.

Alligators

Alligator (Spanish el lagarto,"the lizard"), common name for two carnivorous reptiles in the crocodilian order. Difference from crocodiles: Alligators and their close relatives the caimans have broad, flat, and rounded snouts, as opposed to the longer, sharper snouts of other crocodilians; also unlike other crocodilians, their lower teeth cannot be seen when their mouths are closed. Feeding: Alligators feed on fish, frogs, snakes, turtles, birds, mammals, and carrion. In North America they are also known to attack humans occasionally. Alligators can survive a wider range of temperatures than other crocodilians, and they are found in more temperate regions. Their breeding season is generally restricted to spring.

Reproduction: When alligators search for a mate they bellow often, perhaps to announce their presence to females and to warn other males to stay away. Unwanted intruders are confronted with ritual gaping, lunging, and hissing, but courtship behavior is sedate. After mating, the male seeks his own territory while the female builds a nest of mud and plants nearby, above flood level. The eggs, from 30 to 60 in a clutch, are covered with mud and vegetational debris. The female stands guard as the eggs incubate in the heat from this decaying vegetation and from the sun. When the eggs are ready to hatch, in about 60 days, the young begin to croak softly within the egg. The female may then assist the young in escaping from the nest and may even carry them in her mouth to the water's edge. The female may remain near her young for a year or more. A young alligator in distress will give a series of sharp croaks that may quickly bring the female to investigate.

Only two species of alligator exist: the Chinese alligator and the American alligator. The Chinese alligator makes its home in the Yangtze River Basin of China. It is more timid and much smaller than the American alligator, seldom exceeding 8 ft in length, and is considered little threat to humans. The American alligator lives mainly in freshwater swamps, lakes, and bayous Locations: It is found throughout Florida, south Georgia, Louisiana, and southeast Texas. It is also found near the coast in North and South Carolina and in southern Arkansas. A large size specimen is about twelve feet in length. Feeding: Alligators feed primarily on fish, frogs, snakes, turtles, birds and mammals. Stories abound among farmers in northern Florida of alligators that, when the ponds are dried up and the fish dead or depleted, will attack cattle. in the southeastern United States, but it ranges as far west as the R�o Grande in Texas. It is larger, Size: Authentic records are on file from years ago point out that these animals will grow to eighteen or nineteen feet.., and is potentially dangerous to humans. Attacks occur infrequently, usually in areas where humans have recently encroached on alligator habitat or where alligators have become accustomed to the presence of humans. Became endangered: Hunted for generations both for sport and for its hide, populations of the American alligator dwindled until, in 1967, it was declared an

endangered species. under this protection it made a strong comeback and, little more than a decade later, hunting of the American alligator was again allowed in some states.

Crocodile

Locations: Crocodilians live in tropical and subtropical areas of the world. Modern crocodilians are amphibious, spending much of their time in water, where they swim with rhythmic strokes of the tail. Feeding: The tail is sometimes used to capture prey, sweeping it from shallow to deeper water, where it can be devoured more easily. The jaws of crocodilians are powerful enough in closing to crush the bones of small animals, but so weak in opening that they can be held together by hand.

Traits: Crocodilians are well-adapted as predators, with few natural enemies. Bony plates, called osteoderms, form a kind of armor in their thick skin. Their teeth, about 30 to 40 in each jaw, are set into sockets in the jawbones and interlock when the mouth is closed. In crocodiles, the fourth tooth on each side of the lower jaw protrudes when the mouth is closed; in alligators, these teeth are not visible. As the crocodilian floats almost completely submerged, its protruding nostrils and eyes and a portion of its back are the only parts visible as it stalks its prey. Crocodilians are the most vocal reptiles, producing sounds from quiet hisses to fearsome roars and bellows, usually during the mating season. Locomotion: On land, crocodilians move quickly in a belly crawl but can also gallop and walk mammal-like on all four legs.

Crocodiles are physiologically the most advanced reptiles; their internal anatomy resembles that of birds. They have a four-chambered heart and well-developed senses. Cold-blooded like all reptiles----their body temperature depends on the environment----crocodilians bury themselves in mud to estivate or hibernate. In warm regions they are dormant during droughts; in colder regions, during winter.

Reproduction: Crocodilians are egg-laying, or oviparous, reptiles, reaching reproductive maturity at about the age of ten. The eggs, 20 to 90 in number and about the size of goose eggs, are buried in sand, mud, or vegetable debris, where they are left to hatch by the heat of the sun or of vegetable decomposition. Females of some species remain in the area to protect the nest and care for the newly hatched young, although many of the eggs and young are lost to predators. The parental behavior of crocodilians is unique among reptiles and points to their affinity with birds.

The Crocodile

Some members of the crocodile family are the largest living reptiles. Crocodiles usually can be recognized by their long triangular snouts, intermediate between the long, narrow snouts of gavials and the short, oval snouts of alligators and caimans. Size of largest: The Indo-Pacific, or saltwater, crocodile, possibly the largest living reptile, is known to grow to a length of about 23 ft and to weigh more than 2000 lbs); there are unconfirmed reports of individuals up to 30 ft in length. Locations: This species inhabits the coastal waters of India, southern China, and Malaysia.

The Nile crocodile of Africa was revered by certain ancient Egyptian sects, and mummies of crocodiles have been discovered in Egyptian tombs. In modern times this species has been hunted so extensively that few individuals remain in the lower Nile, but they are still abundant in the upper Nile and southward in Africa to the Cape of Good Hope.

Commercial value: Crocodile eggs are used for food in some parts of the world. The skin is highly valued for leather, and the extract from the musk glands is used in the manufacture of perfumes. Due to overhunting, most crocodiles are considered endangered species.

Turtles

Reptile with a bony or leathery shell. Any shelled reptile can be called a turtle, but in North America people commonly use the word tortoise to designate members of a family of turtles that live entirely on land, reserving the word turtle for species that live in or near water.

Turtles are ancient life forms that survived the disasters that wiped out the dinosaurs and many other creatures at the end of the Mesozoic Era The earliest known fossil turtles were similar to the turtles that live today. Some fossil turtles had teeth, unlike today's turtles, which are toothless and use their sharp jaws to bite and handle food. Early turtles also had not the ability to pull their heads into their shells.

There are about 270 living species of turtles, which are grouped into 12 or 13 families. These families are further classified into two suborders: side-necked turtles and hidden-necked turtles.

Side-necked turtles protect their heads by folding their necks sideways under the top edge of the shell. These turtles are found only in South America, Africa, and Australia and nearby islands.

Hidden-necked turtles pull their heads directly into the shell, using an up-and-down motion of the neck. Hidden-necked turtles are more widespread than side-necked turtles. They include all of the ocean-living and freshwater turtles of North America, Europe, and Asia, as well as the land-living tortoises. Sea turtles, as well as a few other kinds of turtles, are considered members of the hidden-necked group even though they cannot fully withdraw their heads.

Habitats: Turtles inhabit every continent except Antarctica, in habitats as diverse as ponds, rivers, and oceans; forests and grasslands; and even deserts. Like all living reptiles, turtles are ectotherms----cold-blooded animals whose body temperature is influenced by the outside environment. For this reason, turtles are most abundant in warm tropical and subtropical climates. Eastern North America, however, is home to numerous turtle species, despite its temperate climate.

Turtles & humans: Turtles have long fascinated people of many cultures, and they are often used to symbolize wisdom and long life. In many Native American and Asian cultures, turtles are mentioned in myths that explain the origin of the universe. In China and Southeast Asia, turtles are sometimes venerated in religious ceremonies.

Despite the reverence turtles have inspired, these animals have a long history of being used by humans. People in many parts of the world eat turtle flesh and eggs, and use turtle parts in traditional medicines. Turtle fat is a source of valuable oils. Some turtles, such as the hawksbill turtle, are killed for their decorative shells, which are the source of tortoiseshell used in jewelry. In addition, many thousands of turtles and tortoises are collected and sold as pets.

Turtle destruction: By killing turtles, removing turtles from their natural habitats, and destroying the environments in which turtles thrive, humans have brought many turtle species to the brink of extinction.

II. Physical Description

Turtles vary widely in size. The world's largest turtle----the great leatherback sea turtle----reaches a shell length of 96 in. and can weigh over 2,000 lbs. The giant tortoises of the Gal��pagos Islands, near South America can reach at least 50 in in length. The largest North American freshwater turtle is the alligator snapping turtle, which can reach a shell length of 31.5 in..

Among the smallest turtles are the American mud turtles and musk turtles, which have a range that extends from southern Canada through much of South America. Many species in these groups are less than 5 in. in shell length.

A. Shell

The upper shell of the turtle, under which the head, limbs, and tail can be more or less completely withdrawn, is called the carapace. The lower shell, which encases the belly, is called the plastron. The carapace and plastron are joined together on a turtle's left and right sides by bony structures called bridges. The inner layer of a turtle's shell is composed of about 60 bones, including portions of the backbone and the ribs. For this reason, a turtle cannot crawl out of its shell.

Scales or leathery shells: In most turtles, the outer layer of the shell is covered with large horny scales called scutes. The scutes are part of the turtle's outer layer of skin, or epidermis. Scutes are composed of a fibrous protein called keratin, which also makes up the scales of other reptiles. The scutes overlap the seams between the shell bones, adding strength to the shell. Some turtles, like the leatherback sea turtle and the soft-shelled turtles, lack horny scutes, and instead have shells covered with leathery skin.

Some turtles have shells with flexible hinges that allow the turtles to close off the openings in their shells through which they withdraw their heads, tails, and limbs. These hinges protect against predators and help prevent the turtles from drying out when they are on land. The American box turtle has a single hinge across the plastron. American mud turtles have two hinges on their plastrons.

The shape of a turtle's shell provides clues about its way of life. Most tortoises have high, dome-shaped shells. The shape of these shells makes it difficult for predators to crush these turtles between their jaws. Most aquatic turtles have flatter, more streamlined shells, which aid in swimming and diving. American musk and snapping turtles have small, cross-shaped plastrons that enable greater leg movement for walking on the bottom of ponds or streams.

Weight of shells: Tortoises have rather heavy shells. In contrast, sea turtles and soft-shelled turtles that live continuously in water have lighter shells, which help them avoid sinking in water and increase their swimming speed and agility. These lighter shells have large spaces called fontanelles between the bones. The shells of leatherback turtles are extremely light for their size because they contain many fontanelles and lack horny scutes.

Color of shells: Turtle shells are commonly brown, black, or olive green. In some species, shells may have red, orange, yellow, or gray markings. These markings commonly appear as spots, lines, or irregular blotches. An especially colorful turtle is the eastern painted turtle, which has a yellow plastron and a black or olive shell with red markings around its rim.

B. Head

Eyes: Most turtles and tortoises have conspicuous eyes placed well forward on the upper sides of their heads. Turtle species that live most of their lives on land usually focus their eyes downward toward objects in front of them.

Some water-living turtles, like snapping turtles and soft-shelled turtles, have eyes nearer the top of the head. These turtles can hide from predators and prey in shallow bodies of water, where they lie nearly entirely submerged except for their eyes and nostrils.

Sea turtles have glands near their eyes that produce salty tears, ridding the turtles' bodies of the excess salt that they take in from drinking seawater. When a sea turtle is in the water, its tears are immediately washed away, but when these turtles arrive on land, they look as though they are crying.

Jaws: Turtles use their jaws to cut and handle food. Instead of teeth, a turtle's upper and lower jaws are covered by horny ridges, similar to a bird's beak.

Meat-eating turtles commonly have knife-sharp ridges for slicing through their prey.

Plant-eating turtles often have ridges with serrated edges that help them cut through tough plants.

Turtles use their tongues in swallowing food, but unlike many other reptiles, such as chameleons, they cannot stick out their tongues to capture food.

C. Limb Structure

Turtle limbs, used for locomotion, are adapted to their particular habitat.

Land-dwelling tortoises have strong, thick legs to support their heavy shells. They typically move at slow speeds of less than 0.3 mph. The gopher tortoise of the American southeast has flattened front limbs that function as scoops for digging the deep burrows in which it lives.

Aquatic turtles move either by swimming or by walking on the bottom of a body of water, such as a pond. Many aquatic turtles, including painted turtles, sliders, and soft-shelled turtles, have long toes connected by webbing. These turtles spread out their toes to obtain a large surface area for pushing against the water, which helps them to dive and to swim quickly to escape predators. Soft-shelled turtles are the fastest freshwater turtles and can swim faster than most fish.

Sea turtles are the most specialized swimmers of all turtles. Their forelimbs are modified into flipper-shaped blades. These turtles practically fly through the water, using their hind feet primarily as rudders. Despite turtles' reputation for being slow-moving animals, sea turtles can achieve swimming speeds of more than 19 mph, a speed an elite sprinter might reach for a short distance on land.

D. Tail

Most turtles have rather short tails, but the Asian big-headed turtle has an extremely large, muscular tail covered with protective scales that it can use to climb steep rocks and logs in mountain streams. While climbing, these turtles press their tails onto the climbing surface to support their weight. The American snapping turtles also have very long tails. Among most turtle species, males tend to have longer, thicker tails than the females.


E. Physiology

Turtles breathe air with lungs, as do other reptiles and all land-living vertebrates. Since turtle ribs are part of their shell, turtles cannot move their ribs in and out to expand or deflate their lungs. Instead, turtles alternately expand and contract various groups of muscles, including those in their abdomen and above their front and hind legs, to change the amount of space within the shell. When these muscles expand, less space is available and the lungs are compressed, permitting the turtle to exhale. A turtle takes in air as these muscles contract to provide more space into which the lungs can expand.

Many aquatic turtles remain submerged in water for periods of several hours to several days----and for many months during winter hibernation. Many turtles are able to take in oxygen from water through the linings of the mouth, throat, and an internal chamber called the cloaca, as well as through the skin. However, when they are active, aquatic turtles need to rise to the surface periodically to breathe air with their lungs.

Like most reptiles, except for crocodiles and their close relatives, turtles have a heart with three chambers. A turtle's heart operates almost as if it had four chambers, however, because one of its chambers, called the ventricle, has an incomplete divider, or partition. This divider helps prevent the blood that has received oxygen from the lungs and is ready to circulate through the turtle's body from mixing with blood that is depleted in oxygen and needs to travel to the lungs for a fresh supply.

In a turtle's digestive system, food passes from a turtle's mouth through a tubelike esophagus to the stomach, where digestion begins. Food passes from the stomach into the intestine, where nutrients can be absorbed into the bloodstream. Wastes from the intestine are emptied into the cloaca, from which the wastes leave the turtle's body. Turtles also have a urinary system, which filters waste products from the blood and excretes them through the cloaca.

Turtles have a central nervous system and a well-developed brain. They have keen senses that they use to interpret their world. Most turtles have sharp vision and can recognize patterns and colors. The eyes of sea turtles are adapted for seeing underwater, but they can see only short distances when they are on land.

Most turtles, including sea turtles, have a good sense of smell. Both the shells and the skin of turtles are sensitive to touch. Turtles' ability to hear sounds that travel through the air is limited to low frequencies, but they can perceive vibrations transmitted through the ground or water.

A. Temperature Regulation

Like all reptiles, turtles are ectothermic, or cold-blooded, animals that control their body temperature by moving into or out of warm or cool places. Unlike endothermic, or warm-blooded, animals, such as mammals, turtles do not generate heat in their bodies from digesting food.

Leatherback sea turtles are an exception, as they can produce internal heat in their muscles while swimming, and their huge size, together with a thick layer of oily fat under their skin, helps them retain this heat. As a result, they can range into such extremely cold areas as the North Sea. Other marine turtles can survive only in warmer waters.

Many activities of turtles help regulate their body temperatures. Aquatic turtles often leave the water to bask in the sun on logs or rocks or along the banks of lakes and streams to warm their bodies.

In winter, turtles that live in seasonal climates enter a dormant state resembling hibernation. In this state, called torpor, the turtles stop feeding and their oxygen needs become very low.

Aquatic turtles usually remain underwater in winter, relying on their ability to obtain oxygen from water through their skin, throat linings, and sacks within their cloaca.

In contrast, land-living turtles burrow into the soil. Eastern box turtles may spend the winter in shallow burrows; they are able to survive partial freezing of their body fluids for several days. Young painted turtles often spend their first winter in an underground nest. These infant turtles have the ability to survive sub-freezing temperatures for several days.

B. Feeding

Most turtles are omnivores----animals that eat both plants and other animals. Most of the smaller pond-, marsh-, and stream-dwelling species, including the American painted and slider turtles and the European pond turtle, eat insects, snails, worms, minnows, and tadpoles, as well as aquatic plants. The terrestrial box turtles of North America commonly eat small animals, but when ripe berries are available, they may eat so many that they become too fat to close their hinged shells.

Some turtles, such as the South American side-necked turtles and American cooters, are largely herbivorous, eating soft water plants and fruits that fall into the water. Tortoises, which move too slowly to capture most types of animals, are almost entirely plant and fruit eaters, although many species scavenge the remains of dead animals on occasion.

Many species of aquatic turtles are strictly meat-eaters, or carnivores, and some of them specialize in eating certain types of prey. Malaysian snail-eating turtles and American map turtles, especially the larger females, eat mostly snails and clams. These turtles have bony ridges in their mouths that help them crush the shells of their prey. The alligator snapping turtle attracts fish to its open mouth by wriggling an appendage on its tongue that looks like a worm.

The matamata, a side-necked turtle from South America, has an unusual strategy for catching fish. Attached to the matamata's head and neck are numerous flaps that move in the water, possibly causing fish to mistake them for worms or other food. These flaps contain abundant nerve endings that alert the matamata to disturbances in the water,

including those caused by the approach of prey. When a fish comes within range, the matamata lunges with its jaws, sucking the fish into its mouth in a rush of water.

IV. Life Cycles and Reproduction

Female turtles have two ovaries----organs that produce eggs----and male turtles each have a pair of sperm-producing organs called testes. Male turtles, like male crocodiles, have a penis that is located on the lower wall of the cloaca. The penis has a groove on its upper side. During mating, sperm travels along this groove and passes into the cloaca of the female.

Mating among turtles often begins with ritualized courtship behaviors by males. Depending on the species, some male turtles nip at the female's shell or neck, or bob or swing their heads over the female's head. Male painted and slider turtles vibrate their very long foreclaws on the side of the female's head during courtship.

Female turtles that are not ready to mate may pull into their shells or try to escape. Female green sea turtles sometimes avoid a male's advances by swimming away or by folding their hind flippers together.

During mating, the male climbs on top of the female and inserts his penis into the female's cloaca to release his sperm, which will later fertilize eggs from the female's two ovaries. In many species, the male's plastron has an inward curve that helps him balance on the female's shell.

Female turtles of some species, including American box turtles and diamond-backed terrapins, can store sperm and lay fertile eggs for up to four years after a single mating.

Turtles may mate either on land or in water, but all turtles lay their eggs on land. Turtle eggs are either oval or round and are white or nearly white, and they are covered with either thin and flexible or fairly thick and rigid eggshells that protect the eggs from drying out.

Most female turtles bury their eggs in a nest hole that they dig in the ground with their hind feet. This nest site is chosen so that it provides proper warmth and moisture for the eggs, as well as safety from flooding. The number of eggs in a clutch----those eggs laid by a female during one nesting----varies from 1 to about 200, depending on the species. Most small species have clutches of between 1 and 6 eggs, but large species may have clutches that consist of dozens of eggs.

Sea turtles, such as the green turtle, may migrate thousands of miles to find suitable nesting beaches. These turtles must drag themselves along the beach because their paddle-shaped forelimbs are not suitable for walking. After covering the nest with dirt or sand, a female turtle provides no further care for her eggs or young.

Many turtle nests are destroyed by predators, such as raccoons, foxes, and skunks, before the eggs can hatch. If they escape being eaten, the eggs of most turtle species incubate for two or three months before hatching, though a few species, including some of the larger tortoises, require a year or more.

For reasons not well understood, for most turtle species, the temperature of the egg about midway through incubation determines the sex of the hatchling. For example, red-eared slider turtle eggs kept below about 82� F will produce nearly all male hatchlings; if kept above 86� F, they hatch into females. At about 84� F, both sexes may result.

In the American soft-shelled turtles and a few other species, temperature has no effect on a hatchling's sex. In these species, hereditary units called chromosomes may determine sex, as is the case with birds and mammals.

Most baby turtles grow quickly during their first years of life, but growth soon slows. Depending on the species, it may take from 5 to 20 years or more before they are mature and able to reproduce.

Turtles are known for their long life spans. Many of the smaller pond and river species can live over 30 years. American wood turtles, European pond turtles, and snapping turtles may surpass 60 years. American box turtles and European tortoises sometimes reach the century mark, and captive giant tortoises are reported to have lived for more than 200 years.

V. Human Impact

Turtles have been a successful group of animals for A long time, but today the future of many species is in doubt. Though well adapted to survive natural threats, the massive environmental changes caused by human activities are proving to be too much for these long-lived creatures.

Some scientists fear that human actions, including destroying turtles' natural habitats, directly killing turtles, and even removing them from the wilderness areas that remain, may result in the extinction of many turtle species in the next few decades.

Turtles and tortoises are losing vast portions of their original habitats as humans convert wetlands, forests, and grasslands to agricultural fields, grazing lands, and villages and cities.

Pollutants from farms and urban areas have degraded many turtle habitats. Turtles are also harmed when humans alter rivers and streams by creating dams and channels, or build sea walls or jetties on the beaches where sea turtles lay their eggs.

Tortoises, which are especially slow moving and easily captured, have long been hunted by humans for food. During the 18th and 19th centuries, whalers captured vast numbers of giant tortoises from the Gal�pagos Islands to feed to their crews. These ships also harmed tortoises by releasing rats and cats that ate tortoise eggs and young tortoises. By 1900, few tortoises remained, and several forms were already extinct.

Efforts by conservationists to breed Gal�pagos tortoises in protected facilities probably saved them from extinction. Today many smaller mainland tortoise species are also being killed in large numbers and could soon disappear unless efforts are made to save them.

Freshwater and marine turtles may be scattered over their habitats much of the year, but all must return to specific shoreline sites to nest, giving humans the opportunity to take both the female turtles and their eggs for food. These nesting habits leave the turtles vulnerable and nearly all sea turtles and many species of freshwater turtles are now greatly reduced in numbers or even threatened with extinction.

Many sea turtles die in fishing nets, and others are killed when they eat garbage that has been thrown into the ocean. Hawksbill sea turtles are killed for their thick carapace scutes, which provide the tortoiseshell used to make combs, curios, and small art objects.

Sea turtles are also killed to make leather products. In Southeast Asia and China, turtles are both eaten and used in traditional medicine. A greatly increased Asian turtle trade in recent years has brought many formerly common species to the brink of extinction in this region.

The pet trade, which affects mainly small terrestrial and semi-aquatic species, is another threat to turtles. North American box and pond turtles, as well as the small tortoises found in the Mediterranean region, are particularly valuable to pet trade collectors.

In 1975, the United States Food and Drug Agency banned the sale of turtles with shells measuring less than 4 in. because many turtles carry a type of bacteria called Salmonella that can infect humans, causing severe gastrointestinal distress. This ban reflects the concern that young children might put these small turtles in their mouths.

Larger turtles are still sold as pets in the United States, and turtle farmers can legally sell small hatchling turtles from the United States to overseas markets. Due to the pet trade, slider turtles that are native to the southeastern United States have been spread to many parts of the world. In many instances these pets have escaped human homes and started populations in the wild. In some areas, these feral turtles have taken over habitats once used by native turtles.

Compared to other wildlife, turtles are particularly vulnerable to harm from direct exploitation. Turtles' slow pace of reproduction is normally compensated by the long lives of mature adults. Thus, it is difficult for populations to recover after numerous mature adults have been killed or removed. In such cases, the turtle population inevitably declines and may eventually disappear.

Many states and countries have passed laws to protect rare turtle species. More than 130 nations have signed a treaty called the Convention on International Trade in Endangered Species of Wild Flora and Fauna, which regulates the international transport of endangered forms of wildlife, including many turtles and tortoises.

Some countries, including the United States, require large-scale shrimp fisheries to use nets that contain turtle excluder devices. These devices help turtles escape from fishing nets.

Unfortunately, many wildlife laws are difficult to enforce, and developing nations in particular may lack the necessary resources for preventing the exploitation of turtles. Unless people around the world take steps to preserve turtles and tortoises within their natural environments, many species of these intriguing and ancient animals will probably become extinct during the 21st century.

Lizards:

The Komodo Dragon

Found only on a few small islands in the Indonesian archipelago especially the Indonesian island of Komodo, it is the world's largest lizard.

A deer nimbly picks its way down a path meandering through tall savanna grasses. It is an adult male of its species, weighing some 200 pounds. Also known as a Rusa deer, the animal knows this route well; many deer use it frequently as they move about in search of food. This Rusa's home is the Indonesian island of Komodo. Most wildlife find survival a struggle, but for the deer on Komodo, and on a few of the nearby islands, nature is indeed quite red in tooth and claw. This deer is about to encounter a dragon. The Komodo dragon, as befits any creature evoking a mythological beast, has many names.

It is also the Komodo monitor, being a member of the monitor lizard family, which today has but one genus, Varanus. Residents of the island of Komodo may call it the ora. Among some on Komodo and the islands of Rinca and Flores, it is called land crocodile, a name that is descriptive but inaccurate; monitors are not crocodilians. Others call it giant monitor, which is quite correct; it ranks as the largest of the monitor lizards, a necessary logical consequence of its standing as the biggest lizard of any kind now living on the earth. Most everyone also calls it simply the Komodo. The deer has wandered within a few yards of a robust male Komodo, about eight feet long and weighing 100 lbs..

The first question usually asked about Komodos is, how big do they get? The largest verified specimen reached a length of just over 9 feet and was purported to weigh 360 lbs, which may have included a substantial amount of undigested food.

More typical weights for the largest wild dragons are about 155 lbs; captives are often overfed. Although the Komodo can run briefly at fast speeds, its hunting strategy is based on stealth and power. It has spent hours in this spot, waiting for a deer, boar, goat or anything sizable and nutritious.Monitors can see objects as far away as 300 yards, so vision does play a role in hunting, especially as their eyes are better at picking up movement than at discerning stationary objects. Their retinas possess only cones, so they may be able to distinguish color but have poor vision in dim light. Today the tall grass obscures the deer. KOMODO DRAGON flicks his foot-long, yellow forked tongue to taste the air.

Should the deer make enough noise the Komodo may hear it, despite a mention in the scientific paper first reporting its existence that dragons appeared to be deaf. Later research revealed this belief to be false, although the animal does hear only in a restricted range, probably between about 400 and 2,000 hertz. (Humans hear frequencies between 20 and 20,000 hertz.) This limitation stems from varanids having but a single bone, the stapes, for transferring vibrations from the tympanic membrane to the cochlea, the structure responsible for sound perception in the inner ear. Mammals have two other bones working with the stapes to amplify sound and transmit vibrations accurately. In addition, the varanid cochlea, though the most advanced among lizards, contains far fewer receptor cells than the mammalian version. The result is an animal that is insentient to such sounds as a low-pitched voice or a high-pitched scream.

Vision and hearing are useful, but the Komodo's sense of smell is its primary food detector. Its long, yellow forked tongue samples the air, after which the two tongue tips retreat to the roof of the mouth, where they make contact with the Jacobson's organs. These chemical analyzers "smell" the deer by recognizing airborne molecules. The concentration present on the left tongue tip is higher than that sampled from the right, telling the Komodo that the deer is approaching from the left.

This system, along with an undulatory walk in which the head swings from side to side, helps the dragon sense the existence and direction of odoriferous carrion from as far away as four kilometers, when the wind is right. The Komodo makes its presence known when it is about one meter from its intended victim. The quick movement of its feet sounds like a "muffled machine gun," according to Walter Auffenberg, who has contributed more to our knowledge of Komodos than any other researcher. Auffenberg, a herpetologist at the University of Florida, lived in the field for almost a year starting in 1969 and returned for briefer study periods in 1971 and again in 1972. He summed up the bold, bloody and resolute nature of the Komodo assault by saying,

"When these animals decide to attack, there's nothing that can stop them." That is, there is nothing that can stop them from their attempt--most predator attacks worldwide are unsuccessful. The difficulties in observing large predators in dense vegetation turn some quantitative records into best estimates, but it is informative that one Komodo followed by Auffenberg for 81 days had only two verified kills, with no evidence for the number of unsuccessful attempts. For the sake of instructive exposition, the Komodo that has ambushed the deer reaches its target. It attacks the feet first, knocking the deer off balance. When dealing with smaller prey, it may lunge straight for the neck. The basic strategy is simple: try to smash the quarry to the ground and tear it to pieces. Strong muscles driving powerful claws accomplish some of this, but the Komodo's teeth are its most dangerous weapon. They are large, curved and serrated and tear flesh with the efficiency of a plow parting soil. Its tooth serrations harbor bits of meat from the Komodo's last meal, either fresh prey or carrion. This protein-rich residue supports large numbers of bacteria. They have some 50 different bacterial strains, at least seven of which are highly toxic, in the saliva.

If the deer somehow maneuvers away and escapes death at this point, chances are that its victory, and it, will nonetheless be short-lived. The infections it incurs from the Komodo bite will probably kill it within one week; its attacker, or more likely other Komodos, will then consume it.

The Komodo bite is not deadly to another Komodo, however. Dragons wounded in battle with their comrades appear to be unaffected by these otherwise deadly bacteria. Should the deer fail to escape immediately, the Komodo will continue to rip it apart. Once convinced that its prey is incapacitated, the dragon may break off its offensive for a brief rest. Its victim is now badly injured and in shock. The Komodo suddenly launches the coup de gr�ce, a belly attack. The deer quickly bleeds to death, and the Komodo begins to feed. The muscles of the Komodo's jaws and throat allow it to swallow huge chunks of meat with astonishing rapidity: A researcher once observed a female who weighed no more than 110 lbs. consume a 68 lb. boar in 17 minutes. Several movable joints open the lower jaw unusually wide, help in the bolting.

The stomach expands easily, enabling an adult to consume up to 80 percent of its own body weight in a single meal, which most likely explains some exaggerated claims for immense weights in captured individuals. Large mammalian carnivores, such as lions, tend to leave 25 to 30 percent of their kill unconsumed, declining the intestines, hide, skeleton and hooves. Komodos eat much more efficiently, forsaking only about 12 percent of the prey. They eat bones, hooves and

swaths of hide. They also eat intestines, but only after swinging them vigorously to scatter their contents. This behavior removes feces from the meal.

Because large Komodos cannibalize young ones, the latter often roll in fecal material, thereby assuming a scent that their bigger brethren are programmed to avoid consuming.

More Komodos, attracted by the aromas, arrive and join in the feeding. Although males tend to grow larger and bulkier than females, no obvious morphological differences mark the sexes. One subtle clue does exist: a slight difference in the arrangement of scales just in front of the cloaca, the cavity housing the genitalia in both sexes.

Sexing Komodos remains a challenge to researchers; the dragons themselves appear to have little trouble figuring out who is who. With a group assembled around the carrion, the opportunity for courtship arrives. Most mating occurs between May and August. Dominant males can become embroiled in ritual combat in their quest for females. Using their tails for support, they wrestle in upright postures, grabbing each other with their forelegs as they attempt to throw the opponent to the ground. Blood is usually drawn, and the loser either runs or remains prone and motionless. The victorious wrestler initiates courtship by flicking his tongue on a female's snout and then over her body. The temple and the fold between the torso and the rear leg are favorite spots. Stimulation is both tactile and chemical, through skin gland secretions.

Before copulation can occur, the male must evert a pair of penis-like structures located within his cloaca, at the base of the tail. The male then crawls on the back of his partner and inserts one of the two, depending on his position relative to the female's tail, into her cloaca. The female Komodo will lay her eggs in September.

The delay in laying may serve to help the clutch avoid the brutally hot months of the dry season. In addition, unfertilized eggs may have a second chance with a subsequent mating. The female lays in depressions dug on hill slopes or within the stolen nests of certain birds. (These birds make nests composed of heaps of earth mixed with twigs that may reach a meter in height and three meters across.) While the eggs are incubating, female dragons may lie on the nests, protecting their future offspring. No evidence exists, however, for parental care of newly hatched Komodos.The hatchlings weigh less than 3.5 ounces and average only 15 inches in length.

Their early years are precarious, and they often fall victim to predators, including their fellow Komodos. They feed on a diverse diet of insects, small lizards, snakes and birds. Should they live five years, they can weigh 55 lbs. and stretch six feet long. By this time, they have moved on to bigger prey, such as rodents, monkeys, goats, wild boars and the most popular Komodo food, deer. Slow growth continues throughout their lives, which may last more than 30 years.

The World Discovers a Dragon: The West was unaware of the Komodo until 1910, when Lieutenant van Steyn van Hensbroek of the Dutch colonial administration heard local stories about a "land crocodile." Members of a Dutch pearling fleet also told him yarns about creatures six or even seven meters long. Van Hensbroek eventually found and killed a Komodo measuring a more realistic 2.1 meters and sent a photograph and the skin to Peter A. Ouwens, director of the Zoological Museum and Botanical Gardens at Bogor, Java.Ouwens recruited a collector, who killed two Komodos, supposedly measuring 3.1 and 2.35 meters, and captured two young, each just under one meter. On examination of these specimens, Ouwens realized that the Komodo was in fact a monitor lizard. In the 1912 paper in which Ouwens introduced the Komodo to the rest of the world, he wrote simply that van Hensbroek "had received information ... [that] on the island of Komodo occurred a Varanus species of an unusual size." Ouwens ended the paper by suggesting the creature be given the name V. komodoensis.Understanding the Komodo to be rare and magnificent, local rulers and the Dutch colonial government instituted protection plans as early as 1915. After World War I, a Berlin Zoological Museum expedition roused worldwide interest in the animal. In 1926 W. Douglas Burden of the American Museum of Natural History undertook a well-equipped outing to Komodo, capturing 27 dragons and describing anatomical features based on examinations of some 70 individuals.

The Komodo's Future. More than 15 expeditions followed Burden's, but it was Auffenberg who performed the most comprehensive field study, looking at everything from behavior and diet to demographics and the botanical features of their territory. Auffenberg determined that the Komodo is, in fact, rare. Recent estimates suggest that fewer than 3,500 dragons live within the boundaries of Komodo Island National Park. The Komodo is now officially considered a

"vulnerable" species, according to the World Conservation Union; it is also protected under the Convention on International Trade in Endangered Species of Wild Fauna and Flora.

KRAKEN, born at the National Zoo in Washington, D.C., on September 13, 1992, was the first Komodo hatched in captivity outside of Indonesia. She still lives there and is now 34 inches from her snout to the base of her tail and weighs 48 lbs. Another 54 dragons eventually were hatched at the zoo, from eggs produced by Kraken's mother, a gift from Indonesia in 1988. Those dragons are now in zoos across the U.S. and in Japan, Germany, the Netherlands and Singapore.

The Komodo dragon has faced major challenges during the past 20 years that threaten its survival in part of the national park and on Flores. The disappearance of dragons on Padar probably stems from poaching of their primary prey, deer. Policing this rugged and sometimes inaccessible habitat is difficult.

Dinosaurs:

Any of a group (sometimes considered as two separate orders) of extinct reptiles. Their closest living relations are crocodiles and birds. Most dinosaurs were large (up to 90 ft), but some were as small as chickens. They disappeared long ago before there were any humans for reasons not fully understood, although many theories exist.
Classification
There are startling conclusions that scientists have reached about these Mesozoic reptiles lately. Finding vegetation balls in fossilized nests, paleontologists have concluded that dinosaurs piled plants atop their eggs so the rotting greenery would warm the little embryos.

Unearthing nests in which the parent died with its arms outspread and its breastbone on the eggs, the researchers suggest that with its dying breath Mom or Dad tried to protect Junior.

Excavating previously unexplored fossil beds, paleontologists "find at least five or six really great new species every year," says Mark Norell of the American Museum.

In the past 30 years scientists have doubled the number of known dino species, and since 1997 they have discovered nesting sites that shed light on parenting behavior and CAT-scanned skulls to infer what kind of sounds the creatures' air passageways could have made.

Answer: crested duckbills like Parasaurolophus probably squeaked when they were young, then bellowed in ultralow frequencies as adults.

"When I began [in about 1980], we knew almost nothing. It was just piles of bones everywhere," says Paul Sereno of the University of Chicago. "But now dinosaur paleontology has advanced on all fronts."

For instance, scientists unveiled the remains of what seems to be the largest meat-eating dino ever to shake the ground. At 45 feet long, the predator-to-be-named-later was four feet longer than Giganotosaurus, the eight-ton carnivore from South America that was the previous record holder. Six of the newly discovered needle- nosed beasts with razor-sharp choppers were found buried together, in Patagonia. At least three were juveniles. That suggests that although paleontologists "always think of these [carnivores] as solitary," instead they might have lived and hunted in pairs or family packs. "If you're a carnivore and you want to feed off herds, it makes sense to work cooperatively, " says Currie.

Fossils of a 30-foot-tall sauropod (long neck, four legs) that Sereno found in the Sahara last year add to the evidence that some dinos lived in mixed-age herds: an adult Jobaria tiguidensis was found atop a juvenile.
Footprints, too, support the idea of great herds composed of young, old and middle-aged. Norell even suspects that youngsters got corralled into the center of the herd, like baby elephants, for protection. But paleontologist Kenneth Carpenter of the Denver Museum of Natural History is struck by the apparent absence in herds of individuals smaller than half-grown. "They just never occur with the adults," he says. "I suspect the very small ones were segregated until they could keep up." Herds with more than one species were a rarity, too. Footprints offer evidence of who traveled with whom, and they argue against interspecies fraternizing.
Perennial nesting grounds have a firmr basis in fact. At a nesting site discovered in Patagonia in 1997, eggs are nestled in four distinct layers. That suggests that the titanosaurs, long-necked quadrupeds that grew 45 feet long, returned to the flood plain season after season. There must have been hundreds of animals the size of school buses gathering at once. At a nesting ground in Kazakhstan, "eggshells extend along a river for 200 meters vertically. There, too, dinosaurs returned to the same hatchery year after year.
The parenting instinct suggests that dinosaurs had progressed beyond the lay-'em-and-leave-'em school of reproduction. At Egg Mountain in Montana little plant-eating dinos unearthed near the nests of carnivorous dinosaurs appear to be food brought back for the babies. Their arms and legs are often missing, as if they' d been ripped apart by the hungry hatchlings.

Finds from the American Museum's expeditions to Mongolia clearly show that some dinosaurs sat on their eggs and even died on them when sand dunes suddenly collapsed atop them.

Some dinosaurs of Argentina, in contrast, seem to have gone in for community day care. They may have raised the juveniles in a large group that different adults took turns guarding. The young grew up fast.

One of the perennial debates about dinosaurs is whether they were coldblooded (read: slow, sluggish) like reptiles today or warmblooded (quick, energetic) like birds. Today, warmblooded creatures grow fast, and coldblooded ones take their sweet time about it. Analyzing growth rings in the bones of Apatosaurus (once known as Brontosaurus), Kristina Curry of SUNY Stony Brook finds that this giant reached half-size in four or five years, and that reaching adult size took only eight to 11 years. High growth rates are characteristic of warmblooded beasts. Warmbloodedness conjures up a picture of dinosaurs very different from the sluggish beasts of "King Kong"-era movies.

Some scientists would even predict that T. rex had protofeathers, what some people call dinofuzz." (Everyone wants to knock T. rex off his throne: CAT scans of the big guy's skull show that its olfactory bulb is much larger than the brain's visual cortex. Since dead meat stinks more

than the living kind, and since predators need sharp eyesight, the discovery supports the notion that T. rex was a mere scavenger, not a fierce predator.

Species

Brachiosaurus, a long-necked plant-eater was about 40 ft to the top of its head, and weighed 80 tons. Another dinosaur, a meat-eater, was only the size of a chicken, and ran on its hind legs. Stegosaurus, an armoured plant-eater 20 ft long, had a brain only about 1.25 in long.

Not all dinosaurs had small brains. At the other extreme, the hunting dinosaur , 6 ft long, had a brain size comparable to that of a mammal or bird of today, stereoscopic vision, and grasping hands.

Many dinosaurs appear to have been equipped for a high level of activity. Tyrannosaurus was a huge, two-footed, meat-eating theropod dinosaur of the Upper Cretaceous in North America and Asia.

The largest carnivorous dinosaur was Giganotosaurus carolinii. It lived in Patagonia and was 41 ft long, and weighed 6-8 tons. Its skeleton was discovered 1995.

Theories of extinction

A popular theory of dinosaur extinction suggests that the Earth was struck by a giant meteorite or a swarm of comets 65 million years ago and this sent up such a cloud of debris and dust that climates were changed and the dinosaurs could not adapt quickly enough. The evidence for this includes a bed of rock rich in iridium - an element rare on Earth but common in extraterrestrial bodies - dating from the time.

An alternative theory suggests that changes in geography brought about by the movements of continents and variations in sea level led to climate changes and the mixing of populations between previously isolated regions. This resulted in increased competition and the spread of disease.

Archaeological findings

The term 'dinosaur' was coined 1842 by Richard Owen, although there were findings of dinosaur bones as far back as the 17th century. The first dinosaur to be described in a scientific journal was in 1824, when William Buckland, professor of geology at Oxford University, published his finding of a 'megalosaurus or great fossil lizard' found at Stonesfield, a village northwest of Oxford, although a megalosaurus bone had been found in 1677.

An almost complete fossil of a dinosaur skeleton was found in 1969 in the Andean foothills, South America; it had been a two-legged carnivore 6 ft tall and weighed more than 220 lb.

In 1982 a number of nests and eggs were found in 'colonies' in Montana, suggesting that some bred together like modern seabirds.

In 1989 and 1990 an articulated Tyrannosaurus rex was unearthed by a palaeontological team in Montana, with a full skull, one of only six known. Short stretches of dinosaur DNA were extracted in 1994 from unfossilized bone retrieved from coal deposits.

Recent discoveries

The discovery of a small dinosaur was announced in China in 1996. It was 1.6 ft tall. It had short forelegs, a long tail, and short feathers, mainly on its neck and shoulders.

In 1997 US scientists claimed that 65 million-year-old remains discovered in the Atlantic Ocean were proof that a massive asteroid impact on Earth killed the dinosaurs. A sea-drilling expedition discovered three samples that have the signature of an asteroid impact. Previous evidence from sediment suggested that the dinosaurs did not become extinct at exactly the same time as an impact occurred. The new evidence appeared to substantiate the theories of geologists such as Walter Alvarez, who championed the theory that the dinosaurs disappeared from fossil history because of such an impact.