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All About Sharks!
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Acanthodians were the earliest jawed vertebrates. These early fish (Class acanthodii) lived from the Ordovician to the Carboniferous period. Although most Acanthodians were small, averaging roughly 5-6 inches (13-15 cm) long, some were much larger (for example, the genus Xylacanthus, known from its huge jaws, is thought to have been perhaps 3 feet (1 m) long). Some Acanthodians may have been primitive shark-like fish.
Ray-finned fish (class Actinopterygii) are the largest group of fish. These bony fish evolved during the very end of the Silurian, about 408 million years ago. These fish dominate the seas today. Sharks are not ray-finned fish.
Ammonite was an early mollusk, a fast-moving predatory marine invertebrate. These cephalopods are now exinct.
Amniotes are animals whose eggs contain an amnion, a membrane that surrounds the embryo and helps retain fluids. Mammals (including whales), birds, dinosaurs, turtles, and lizards are amniotes.
Amphibians (meaning "double life") are vertebrate animals that live in the water during their early life (breathing through gills), but usually live on land as adults (and breathe with lungs). They include frogs, toads, newts, salamanders, etc.
Amphipods (meaning "double foot") are tiny shrimp-like crustaceans that live in the water. They are marine invertebrates under an inch long that have an exoskeleton and jointed legs. They are eaten in huge numbers by filter feeders such as the whale shark, the basking shark, the megamouth shark, and baleen whales.
Anadromous means migrating to fresh water (from salt water) to breed. For example, some salmon are anadromous.
Anal fins are paired fins near the tail end of some fish. Some sharks have an anal fin, including the follwing orders:Carcharhiniformes, Lamniformes, Orectolobiformes, Heterodontiformes, and Hexanchiformes.
Anapsids include the turtles and their extinct kin. They are distinguished by having no holes in the sides of their skulls.
Squatina, also known as monkfish, are flat-bodied, bottom-dwelling sharks with a blunt snout.
Antarctica is an icy continent around the South Pole.
Anterior means located on or near the front of an animal's body.
Aplacental viviparity (which used to be called ovoviviparity) is when animals hatch from eggs, but the eggs hatch and the babies develop inside the female's body. There is no placenta to nourish the pups. Great white sharks reproduce in this manner.
(pronounced ark-ee-TOO-this) Architeuthis is the giant squid. It is the largest squid and the largest invertebrate (animal without a backbone), but it has never been seen since it lives very deep in the oceans. The largest-known Architeuthis was 57 feet (17.5 m) long. It has eight arms, two longer feeding tentacles, a beak, a large head, and two eyes larger than basketballs! These soft-bodied cephalopods are fast-moving carnivores that catch prey with their tentacles, then poison it with a bite from beak-like jaws. They move by squirting water through a siphon, a type of jet propulsion. Only dead examples of Architeuthis have been found. Its only enemy is the sperm whale who hunts it deep in the ocean.
The Arctic is the area around the North Pole. There is no land under the arctic ice, but it is home to many animals. The only shark that remains in Arctic waters year-round is the Greenland shark.
Arthropods are a group of animals with exoskeletons made of chitin, segmented bodies and jointed limbs. Insects, arachnids, trilobites, crustaceans (like amphipods, krill and copepods), and others are arthropods.
ATLANTIC SHARPNOSE SHARK
The Atlantic Sharpnose Shark (Rhizoprionodon terraenovae) is a harmless, edible, requiem shark (Family Carcharinidae). The Sharpnose is a small, slender shark with 5 gill slits, two dorsal fins, an anal fin, no fin spines, the mouth behind the eyes, and nictitating eyelids. It has a long, sharp snout, black-edged dorsal and caudal fins (which fade with age), and furrowed or wrinkled corners of the mouth. It is brown to olive-gray colored with white countershading on the belly and is from 2 to 4 feet (60-120 cm) long. A carnivore, it eats small fish, mollusks, and shrimp. The sharpnose is viviparous, with litters of 4 to 7 pups. Classification: Order Carcharhiniformes
Everything is made up of tiny atoms. An atom is the smallest part of an element that has the properties of that element.
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