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Enchanted Learning All About Sharks!

Geologic Time Chart

Shark Glossary

PACIFIC ANGELSHARK Squatina californica, also known as the monkfish, are flat-bodied, bottom-dwelling sharks with a blunt snout. It was named by Ayres in 1859. Classification: Order Squatiniformes, Family Squatinidae (Angel Sharks), genus Squatina, species californica.

PACIFIC PORBEAGLE The Pacific Porbeagle (Lamna ditropis, also known as the Salmon shark) is found in the Bering Sea and off western North America. It lives from the surface down to moderate depths. The skin is dusky gray above and paler below with white markings. A strong swimmer, it has a wide tail that has a double keel (a second, short ridge running along the upper part of the lower lobe of the tail). A double keel is unusual among sharks; the only other double-keeled tail is on the closely-related Porbeagle Shark, Lamna nasus.] The largest-known Pacific Porbeagle was 10 ft (3 m) long. Classification: Order Lamniformes (mackerel sharks), Family Lamnidae (Mackerel sharks, porbeagles, and white sharks).

PALEONTOLOGY Paleontology is the branch of biology that studies the forms of life that existed in former geologic periods, chiefly by studying fossils.

PALEONTOLOGIST A paleontologist is a scientist who studies paleontology, the forms of life that existed in former geologic periods, chiefly by studying fossils.

PALEOZOIC ERA The Paleozoic Era (540 to 245 million years ago) saw an explosion of new life forms. It ended with the largest mass extinction in history and was followed by the Mesozoic Era.

PANGAEA Pangaea was a supercontinent consisting of all of Earth's land masses. It existed during the Permian and Jurassic period. It began breaking up during the Jurassic period, forming continents Gondwanaland and Laurasia, separated by the Tethys Sea.

PECTORAL Pectoral means of, pertaining to, or near an animal's chest area.

PECTORAL FLIPPER Pectoral flippers are wide, flat limbs located in the chest area that many marine animals use for swimming.

PELAGIC Pelagic means of, pertaining to, or living in the open ocean, either at the surface or at intermediate depths.

PERIOD The period is the basic unit of geological time in which a single type of rock system is formed, lasting tens of millions of years.

PERMIAN PERIOD Also known as "The Age of Amphibians" (280 to 245 million years ago), this is the time when Pangaea formed and Earth's atmosphere was oxygenated to modern levels. It ended with the largest mass extinction and was followed by the Mesozoic Era. Ancient sharks swam the seas during the Permian period.

PILOT FISH Pilot fish (Naucrates ductor) are small fish that live on and around sharks. They eat stray bits of food left by the shark. The shark does not benefit from the pairing; this is a commensal relationship.

PINNIPEDS The pinnipeds (Order Pinnipedia) are marine mammals that include sea lions, fur seals, and true seals. They are carnivores that are distantly related to dogs and bears. Many sharks eat pinnipeds, including the great white shark.

PLACODERM Placoderms (meaning "plated skin") were armored fish that evolved during the Silurian Period, about 420 million years ago. They diviersified and came to dominate the seas by the Devonian. They went extinct bout 355 million years ago. They had hinged bony armor on their head and thorax. They had no teeth, but did have bony reidges that acted like teeth. Some placoderms included Antiarchi, Bothriolepis, Dunkleosteus (the largest placoderm), Groenlandapsis, and Phyllolepis. Placoderms were early fish, but not sharks.

PLACOID SCALES Placoid scales are tiny, hard, tooth-like structures, also called dermal denticles. They have the same structure as a tooth, having an outer layer of enamel, dentine and a central pulp cavity. Sharks' teeth and skin are composed of placoid scales.

PLANKTON Plankton are tiny marine animals and plants that drift along with ocean currents, living near the surface. The whale shark and the megamouth shark are filter feeders that eat plankton.

PLESIOMORPHY Plesiomorphy (meaning "old form") is a primitive character of a group.

PLESIOSAUR Plesiosaurs were flippered marine reptiles from the Mesozoic Era - they were not dinosaurs.

PLEISTOCENE (pronounced PLEES-toh-seen) The Pleistocene was an epoch in geologic time that lasted from 1.8 million years ago until about 10,000 years ago (it was at the beginning of the Quaternary period). During this epoch, the first humans (Homo sapiens) evolved. Mammoths, mastodons, saber-toothed cats, giant ground sloths, and other Pleistocene megafauna (huge animals) lived. A mass extinction of large mammals and many birds happened about 10,000 years ago (at the end of this epoch), probably caused by climate changes (the last Ice Age ended).

PLIOCENE (pronounced PLEE-oh-seen) The Pliocene was an epoch in geologic time that lasted from 5-1.8 million years ago (it was at the end of the Tertiary period). During this epoch, the first hominids (australopithecines) and modern forms of whales appeared. The ancient shark megalodon swam the seas during this time.

POD A pod is a social group of whales. Baleen whales travel alone or in small pods. The toothed whales travel in large, sometimes stable pods; they frequently hunt their prey in groups, migrate together, and share care of their young.

POIKILOTHERMS Poikilotherms are animals whose internal temperature changes depending on the environment. Reptiles are poikilothermic.

POLYPHYLETIC A polyphyletic group consists of organisms but not their common ancestors. This is an artificial group which is based primarily on physical characteristics rather than on evolutionary relationships. An example is "flying vertebrates" which includes birds, pteranodons and bats.

PORBEAGLE SHARK The porbeagle (Lamna nasus) is a common, fast-swimming, potentially dangerous shark. This mackerel shark can grow to be up to 12 feet (3.7 m), weighing about 350-550 pounds (155-225 kg). They are dark gray on top and white underneath; there is also a small patch of white on the rear edge of the dorsal fin. Porbeagles have a torpedo-shaped body and two keels on the wide tail (the second keel is a short ridge running along the upper part of the lower lobe of the tail), making it an efficient swimmer. The porbeagle feed on fish (mostly mackerel, squid, cod, hake, flounder and other bottom-dwelling fish) with its long, sharp teeth. It lives in cold waters down to about 1,200 feet (370 m). It must swim continuously to get oxygen. Porbeagles are functionally warm-blooded; they retain the heat generated by their muscles and recycle it to heat their body, keeping their body temperature up to 20°F (11°C) warmer than the cold waters they live in. Porbeagles are viviparous, with cannibalistic embryos in the womb; only 2-4 pups survive pregnancy. They live in the North and South Atlantic and the South Pacific Oceans. Order Lamniformes.

PORT JACKSON SHARK Heterodontus portusjacksoni is a harmless, sedentary shark from southern Australia. They can grow to be about 5.5 feet (1.7 m), but are, on average a bit smaller. They are light brown, have distinctive bumps over their eyes, a pig-like snout, and some dark brown stripes on the upper back. The teeth are unusual; there are molar-like (wide and flat) teeth in the front of the mouth and small, sharp teeth in the back of the mouth. Port Jackson sharks mostly stay in shallow-water caves and reefs. These sharks are oviparous, laying eggs among the rocks with corkscrew-like spiral cases. Order Heterodontiformes.

PORTUGUESE SHARK The Portuguese shark, also known as the Portuguese dogfish shark, Centroscymnus coelolepsis, is a chocolate brown shark that is up to 3.8 feet (1.1 m) long (males and females are the same size); the average size is 3 feet (92 cm) long. Juveniles have dark blue skin. It has a heavy body and two tiny dorsal fins with small spines (there is no anal fin). The skin has big, scale-like dermal denticles. The upper teeth are long, pointed, and not serrated; the lower teeth are short and wide. It eats squid and bottom dwelling fish. This bottom-dwelling shark has been netted a depths to 8922 feet (2640 m) - the deepest for any shark. It is ovovivparous; litters have from 13 to 16 pups. Newborns are from 11 to 12 inches (27 to 30 cm) long. The Portuguese shark is found in the Atlantic Ocean, the Mediterranean Sea, and the Pacific Ocean. Classification: Order Squaliformes, Family Squalidae (dogfish sharks), Genus Centroscymnus, species C. coelolepsis.

PREDATOR A predator is an animal that hunts and kills other animals for food.

PREHISTORIC Prehistoric refers to the time before people began recording history in writing. This time varies from culture to culture.

PRISTIOPHORIFORMES A clade of shark that has a long snout, no anal fin, and the mouth underneath. These include the sawsharks.

PRODUCER A producer (or aurotroph) is an organism that makes its own food from light energy (using photosynthesis), or chemical energy (using chemosynthesis). Most green plants, many protists (one-celled organisms like slime molds) and most bacteria are producers. Producers are the base of the food chain.

PUP A pup is a newly-born or newly-hatched shark. Shark pups look like tiny versions of their parents. Pups generally have the same coloration and relative dimensions as adult sharks.

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