SHARK CLASSIFICATION

There are over 350 species of sharks known worldwide. Sharks are classified as follows: 

Kingdom Animalia
Phylum Chordata
SubPhylum Vertebrata
Class Chondrichthyes (cartilaginous fish)
Subclass Plagiostomi (sharks and rays: upper jaw hung from skulls and different kind of blood)
Superorder Selachimorpha (sharks: free upper eyelids, gill openings on the head, and pectoral fins separate from the side of the head)
Subclass Elasmobranchii (upper jaw that is not fused to the braincase, no swim bladder, advanced electroreceptive system, a spiracle, skin with placoid scales, teeth modified placoid scales, and 5-7 separate slit-like gill openings on each side of the body: there are about 600 species of sharks, skates, and rays) 

Living sharks are divided into 8 Orders:

• Squatiniformes (flat body, mouth at front, no anal fin) - angelsharks, monkfish
• Pristiophoriformes (long snout, mouth underneath, no anal fin) - sawsharks
• Squaliformes (short snout, mouth underneath, no anal fin) - dogfish and cookiecutter sharks
• Carcharhiniformes (anal fin, 5 gill slits, 2 dorsal fins, no fin spines, mouth behind the eyes, nictitating eyelids) - ground sharks, including catsharks, swellsharks, shysharks, houndsharks, weasel sharks, requiem and hammerhead sharks
• Lamniformes (anal fin, 5 gill slits, 2 dorsal fins, no fin spines, mouth behind the eyes, no nictitating eyelids) - mackerel sharks, including the basking, goblin, megamouth, great white, crocodile shark, thresher, porbeagles, mackerel sharks, sandtiger, and mako sharks
• Orectolobiformes (anal fin, 5 gill slits, 2 dorsal fins, no fin spines, mouth in front of the eyes) - carpet sharks including the wobbegong, nurse, bamboosharks, blind, zebra, and whale shark
• Heterodontiformes (anal fin, 5 gill slits, 2 dorsal fins, dorsal fin spines) - bullhead, horn sharks
• Hexanchiformes (anal fin, 6-7 gills, 1 dorsal fin) - frilled and cow sharks - having six or seven gills on each side of the head.

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CHARACTERISTICS OF THE EIGHT ORDERS OF SHARKS

No anal fin	Flattened body, mouth at the front.	.	SQUATINIFORMES (Angelsharks)
	Body not flattened, mouth underneath	Snout long and saw-like	PRISTIOPHOROFORMES (Sawsharks)
		Short snout	SQUALIFORMES (Dogfish sharks)

Anal fin present	5 gill slits, 2 dorsal fins	No fin spines	Mouth extends behind the eyes	Nictitating eyelids	CARCHARHINIFORMES (Requiem sharks and hammerheads)
				No nictitating eyelids	LAMNIFORMES (Mackerel sharks)
			Mouth ends in front of eyes	.	ORECTOLOBIFORMES (Carpet sharks)
		Has dorsal fin spines	.	.	HETERODONTIFORMES (Bullhead sharks)
	6 - 7 gill slits, 1 dorsal fin	.	.	.	HEXANCHIFORMES (6-Gilled and 7-Gilled sharks)

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EXTINCT SHARKS

EVOLUTION OF SHARKS
Sharks have existed for over 350 million years. They evolved over 100 million years before the dinosaurs did. This was long before people evolved. Most fossil evidence of early sharks is from fossilized teeth. Cladodonts, primitive sharks, had double-pointed teeth, were up to 3 feet (1 m) long fish-eaters and lived about 400 million years ago (mya). Modern forms of sharks evolved during the Jurassic period, about 150 mya.



Shark fossils are rare because sharks have no bones, only cartilage, which does not fossilize well. 

Cladoselache
The earliest complete fossil shark,Cladoselache, is from the late Devonian. It had 3-pointed teeth with a large central point and smaller cusps flanking it. It was 1.5-6 feet (0.5-2 m) long and had large spines in front of each of the 2 dorsal fins. It had neither an anal fin nor claspers. There were 5 gill slits on each side of the head. Fossils found in the Cleveland shale include fossilized stomach contents which reveal that it ate crustaceans. 

Stethacanthus
A strange-looking shark with brush-like denticles on its head and on a parge protrusion on its back. It had fin spines, an anal fin, and was about 3 feet (1 m) long. 

Orthacanthus
Orthacanthus was an ancient, fresh-water shark that had a long spine growing from the back of its skull. It had a very long dorsal fin, which ran all along the sharks back, giving it an eel-like appearance. Order Xenacanthiformes. 

Hybodus
An ancient shark from the Carboniferous period, this shark went extinct during the huge K-T mass extinction 65 million years ago, when the dinosaurs died. It had fin spines, an anal fin, and was about 7.5 feet (2.5 m) long. 

Megalodon

Megalodon (Carcharodon megalodon) was an ancient, meat-eating shark, living between 5-1.6 million years ago; it is extinct. It was up to 40 feet (12 m) long, but this is only an estimate from fossil teeth that have been found. Its teeth resemble those of the great white shark but are almost 3 times larger. 

FOSSILIZED TEETH
Sharks teeth are the most likely part of its body to fossilize since they're composed of bone. Many fossilized sharks teeth have been found, including that of megalodon. Megalodon (Carcharodon megalodon) was an ancient, meat-eating shark, living between 5-1.6 million years ago; it is extinct. It was up to 40 feet (12 m) long, but this is only an estimate from fossil teeth that have been found. Its teeth resemble those of the great white shark but are almost 3 times larger.

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SHARK EXTREMES

BIGGEST LIVING SHARKS
The biggest shark is the whale shark (Rhincodon or Rhiniodon typus), which can be up to 50 feet (15 m) long. It is a filter feeder and sieves enormous amounts of plankton to eat through its gills as it swims. It is also the biggest fish. The second biggest fish and shark is the basking shark (Cetorhinus maximus) which is about 40 feet (12.3 m) long and is another filter feeder. 

The biggest meat-eating sharks are the Greenland shark and the Great white shark (Carcharodon carcharias) which grow to be up to 21 feet (6.4 m) long. Great whites up to 37 feet (11.3 m) long have been reported, but not verified. 

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SCARIEST SHARK EVER (NOW EXTINCT)
The largest shark known was the Megalodon (Carcharodon or Carcharocles megalodon); it is now extinct. It was an ancient, meat-eating shark that lived between 25 million and 1.6 million years ago. It was up to 40 feet (12 m) long and its teeth were each the size of a person's hand! 

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SMALLEST
 The smallest sharks are:

• Dwarf Lanternfish (Etmopterus perryi), which is about 7 1/2 to 8 inches (19 - 20 cm) long for fully-grown females and 6 to 7 inches (16 - 17.5 cm) long for adult males
• Spined pygmy shark (Squaliolus laticaudus), which is about 8 inches (21 cm) long for fully-grown females and 7 inches (18 cm) long for males
• Pygmy ribbontail catshark (Eridacnis radcliffei) , which is about 6 to 7 inches (15 - 16 cm) long for fully-grown females and 7 to 7 1/2 inches (18 - 19 cm) long for males.

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MOST DANGEROUS
The oceanic white-tipped sharks are the most fearless predators. Jacques-Yves Cousteau says that it is: "the only species of shark that is never frightened by the approach of a diver, and they are the most dangerous of all sharks." 

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FASTEST
The fastest swimming sharks are the mako sharks and blue sharks, which can even leap out of the water. They are also among the fastest fish. Estimates of their speed varies; some say that they can swim at about 60 miles per hour (97 kph), while more conservative estimates are about 22 mph (35 kph). There hasn't been enough observation of their speeds to have a definitive answer. 

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BIGGEST MOUTH
The whale shark has the biggest mouth among sharks. 

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LONGEST TAIL
The thresher sharks have the longest tail among sharks; the upper lobe of their tails are about the same length as their bodies. 

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STRONGEST SHARK BITE
The strongest shark bite belongs to the dusky shark (Carcharhinus obscurus); its jaws have been measured to exert 132 pounds (60 kg) of force per tooth (James Snodgrass and Perry Gilbert, 1965). 

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MOST COMMON SHARK
The piked dogfish shark (Squalus acanthias) is very abundant, especially in the North Atlantic Ocean. It is a small shark, about 63 inches (1.6 m) long. 

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LARGEST EGGS
The whale shark was long thought to be oviparous (an egg 14 inches (36 cm) long was found in the Gulf of Mexico in 1953; this would be the largest egg in the world). Recently, pregnant females have been found containing hundreds of pups. Whale sharks are viviparous, giving birth to live young. Newborns are over 2 feet (60 cm) long. 

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DEEPEST DIVER
The Portuguese shark dives down over 9,000 feet (2750 m). This is over 1.5 miles. 

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LONGEST MIGRATION
The Blue shark had been known to migrate from 1,200-1,700 miles (2000-3000 km) in a seasonal journey from New York state in the USA to Brazil. 

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LARGEST LITTER
One Blue shark was found with 135 pups in her uterus.

For further information log on website :
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SHARK AND RAY INFORMATION SHEETS

There are about 350 different species of sharks, which are divided into 8 orders and 30 families. Below is a sampling of shark species. 

Just click on a shark to go to that information sheet. The drawings are not to scale. 

ANGELSHARK	BASKING SHARK	BLACKTIP REEF SHARK	BLUE SHARK
BLUNTNOSE SIXGILL SHARK	BONNETHEAD SHARK	BROADNOSE SEVENGILL SHARK	BULL SHARK
DOGFISH SHARK	GALAPAGOS SHARK	GOBLIN SHARK	GREAT WHITE SHARK
HAMMERHEAD SHARK	LEMON SHARK	MANTA RAY	MAKO SHARK
NURSE SHARK	PORBEAGLE SHARK	SPINED PYGMY SHARK	THRESHER SHARK
TIGER SHARK	WHALE SHARK

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Shark Anatomy and Physiology

GENERAL ANATOMY

Sharks are fish that have no bones, only cartilage. They have 5-7 gills (without gill covers, operculum) in front of their pectoral fins (on both sides). Shark tails are asymmetrical; the top lobe of tail is larger than the bottom lobe. The shark's jaw is not fused to the braincase and can enlarge to eat very large prey. Sharks have no swim bladder for buoyancy (like the bony fishes); an oily liver aids buoyancy. Sharks have an advanced electroreceptive system that detects slight electrical fields.

The teeth and skin are modified placoid scales. A spiracle (a special gill slit that supplies oxygen directly to the eyes and brain) is present in front of the first gill. Sharks' teeth are replaceable when they've broken or worn out. Their intestines are short and compact and have an unusual structure; a spiral valve (shaped like a spiral staircase) fills the cylindrical intestines and allows absorption of the food in a short span of intestine.

MAJOR DIFFERENCES BETWEEN SHARKS AND BONY FISH

ATTRIBUTE	SHARKS	BONY FISH
Skeleton	Cartilage only	Bones and cartilage
Swimming	Can only swim forward.	Can swim forwards and backwards
Buoyancy (floating)	Large oily liver	Gas-filled swim bladder
Gills	Gill slits but no gill cover	Covered gill slits
Reproduction	Eggs fertilized in female's body.	Eggs usually fertilized in the water.
Skin	Rough, sandpaper-like placoid scales	Slippery, overlapping scales

SHARK ANATOMY

General Anatomy Shape Skeleton Size Life Span

Teeth Skin Digestion Diet, Drinking Tongue

Male or Female? Reproduction Gills, Spiracles Swimming Liver, Buoyancy

Brain Senses Heart, Circulatory System Hot- or Cold-Blooded

For further information log on website :
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What is a Ray?

What is a Ray?

Rays are a type of flattened fish and are closely related to sharks. Rays evolved from sharks. These social animals live in seas all over the world, and even in some estuaries. Rays often congregate in huge groups of up to thousands of individuals, but other rays live alone.

Unlike other fish, rays and sharks have no bones; their skeleton is made of cartilage, which is a tough, fibrous substance, not nearly as hard as bone. 

Many rays have spines on their tail which can poison other animals when stung. Some rays have long, whip-like tails, other species have short tails. Some rays have a series of thorns on their body as a defense against predators. The color variation among rays is huge; color even varies from male to female in some species. 

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SIZE

Rays range in size from just a few inches to over 22 feet wide. The smallest ray is the Short-nose electric ray, which is the size of a pancake; it is only 4 inches (10 cm) across and weighs about 1 pound (0.5 kg). The biggest ray is the manta ray which is over 22 feet (6.7 m) wide and weighs many tons (thousands of pounds). Most rays are in-between these two extremes. More than half of all ray species are over 20 inches (50 cm) long. In fact, rays are some of the largest fish in the sea!

Manta ray Manta birostris is the largest ray. This graceful swimmer is up to 29.5 ft (9 m) wide. Mantas eat microscopic plankton, small fish, and tiny crustaceans. They funnel the food into their mouth while they swim, using two large, flap-like cephalic lobes which extend forward from the eyes.

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BODY SHAPES

The Bluespotted Ribbontail Ray Taeniura lymna is a very common, timid ray with an oval-shaped disc and two venomous tail spikes toward the tip of its tail. It grows to be 2.25 ft (0.7 m) long.

Rays have a flattened body shape and an elongated tail. The pectoral fins are large and connected to the body to form the ray's "disc." The shape of the disc differs from species to species and may be circular, oval, wedge-shaped or triangular. Some body shapes are adapted for living on the sea bed; others are adapted for almost constant swimming. The ray's distinctive tail also varies from species to species. It ranges from stubby (on the Shorttailed electric rays) to incredibly long (e.g., over 10 feet (3 m) long on the Whip-like sting rays).

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VARIETIES OF RAYS
There are about 500 different living species of rays and skates, which are divided into 18 families. These different families of rays are very different in the way they look, live, and hunt. They have different shapes, sizes, color, fins, teeth, habitat, diet, personality, method of reproduction, and other attributes. 

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SKELETON

Rays have no bones; their skeleton is made of cartilage.

Rays and sharks are a type of fish that have no bones, only cartilage. Some parts of their skeleton, like their vertebrae, are calcified. Cartilage, a strong fibrous substance, is softer than bone; our nose and ears are made of cartilage. Even the ray's skull is flattened. Rays belong to the group of fishes called Elasmobranchii, which also includes the sharks, skates, and ratfish. The Elasmobranchii are all fish that have no bones, only cartilage.

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DIET AND HUNTING
Rays vary in their diets, but they are all carnivores. They eat fish, crustaceans, mollusks, and worms. Rays mostly hunt on or near the bottom of the ocean. 

• Some (like the manta ray, which is the largest ray) are filter feeders, sieving small prey (like microscopic plankton, small fish, and small crustaceans) as they swim almost continuously.
• Some rays are active hunters (of bottom-dwelling animals like mollusks and crustaceans). They find the prey on the ocean floor, dislodge it from the floor, grab it (with the rostral lobes), crush it with the teeth (which are mostly flattened plates), and eat it.
• Electric rays (numbfish) stun their prey with electricity.

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INTELLIGENCE
Rays have a high ratio of brain weight to body weight; they are probably very intelligent, even smarter than sharks. They are known to be very curious animals, often approaching a diver and simply observing the intruder. 

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HABITAT
Rays live in oceans and seas all over the world, and some even spend part of their life in estuaries. Rays live mostly on or near the sea bed. Different ray species are found in habitats ranging from close to shore to the extreme depths of the ocean (over 10,000 feet = 3,000 m deep). 

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SWIMMING
Rays swim very differently than other fish. They are propelled through he water with their powerful, wing-like pectoral fins which ripple and flap. Their large pectoral fins also let them glide trough the water. Some rays (like the Mangrove stingray) can even jump above the water.

Many species of rays are coated with a slimy mucous which reduces the surface tension and drag of the water and increases swimming speed.

Like sharks, rays lack a swim bladder and use their oily liver to maintain buoyancy (other fish use an air-filled bladder to help them float). When a ray stops swimming, it sinks down to the sea bed. 

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RAY DEFENSES

Rays defend themselves from predators in many ways. Some use a whip-like tail to lacerate an enemy, some sting enemies with a poisonous stinging tail, electrical rays give electrical shocks (up to 200 volts), and some have hard, bony spines that puncture their victims. Teeth are not used very much by rays as a defense, although some can bite. Camouflage on the sea bed is probably among their best defenses. Rays do not normally attack people. There are some rays who have a tail sting that can be deadly.

Blind Electric Ray Typhlonarke aysoni can give an electrical shock and has almost useless eyes. This poorly-known ray uses electroreceptors to "see." This numbfish has one dorsal fin and lives at great depths (200-900 m).

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RAY REPRODUCTION
Some rays are oviparous (laying eggs) while others reproduce via aplacental viviparity (giving birth to live young that develop in the womb without a placenta). All skates are oviparous. Fertilization is always internal.
Rays and skates have a long gestation period and produces relatively few young (compared to other fish). The growth of ray populations, therefore, is slow.

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FOSSIL RAYS
The earliest known rays (probably guitarfish) date from the Jurassic period, about 150 million years ago. Since rays have no bones (only cartilage), fossil rays are rare, but their teeth, composed of very hard enamel, fossilize well. Many fossilized Guitarfish teeth and some fossilized spines have been found. 

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RAY PRINTOUT
A printout for elementary school students.
Manta ray printout

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CLASSIFICATION OF RAYS
Kingdom Animalia
Phylum Chordata
SubPhylum Vertebrata
Class Chondrichthyes (cartilaginous fish)
Subclass Elasmobranchii (upper jaw that is not fused to the braincase, no swim bladder, advanced electroreceptive system, a spiracle, skin with placoid scales, teeth modified placoid scales, and 5-7 separate slit-like gill openings on each side of the body: sharks, skates, and rays)
Superorder Batoidea - Rays and skates (about 480 species)
Orders - Rays and skates are divided into the following orders:

• Pristiformes - saw-like snout (e.g., the saw fish)
• Rhinobatiformes - 2 dorsal fins (the first closer to pelvis), no electric organ (e.g., the guitarfish, banjo shark)
• Torpediniformes - 2 dorsal fins (the first closer to pelvis), electric organ (e.g., the electric rays)
• Rajiformes - if 2 dorsal fins (the first closer to tail), pelvic fin divided into two lobes (e.g., skates)
• Myliobatiformes - if 2 dorsal fins (the first closer to tail), pelvic fin with one lobe
  • head indistinguishable from disc (e.g., stingrays like the bat ray)
  • head partially distinct from body (e.g., eagle and devil rays)

For further information log on website :
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