ZoomDinosaurs.com Dinosaur and Paleontology Dictionary

Pb Pb is the symbol for the element lead.

PECTINODON (pronounced peck-TIN-oh-don) Pectinodon (meaning "comb tooth") was a meat-eating dinosaur from the late Cretaceous period, about 73-65 million yeas ago. Pectinodon was named by Carpenter in 1982. The type species is P. bakkeri. Pectinodon is an invalid genus - see Troodon.

PEISHANSAURUS (pronounced PAY-shan-SAWR-us) Peishansaurus (meaning "Peishan [China] lizard") was a plant-eating dinosaur that lived during the late Cretaceous period, roughly 97.5-65 million years ago. Peishansaurus was named by Bohlin in 1953 from a fragmentary jaw with some teeth (found in China). The type species is P. philemys. Peishansaurus is a doubtful genus; it is either an an ankylosaur armored dinosaur) or a pachycephalosaur (thick skulled dinosaur).

PELECANIMIMUS (pronounced PEL-uh-kan-uh-MEEM-us) Pelecanimimus (meaning "pelican mimic") was a meat-eating dinosaur from the early Cretaceous period, roughly 132-121 million years ago. Pelecanimimus is the first ornithomimosaur discovered in Europe. It had about 220 teeth, more than any other known theropod. It was about 6.5 ft (2 m) long. It had a dewlap (a loose fold of skin hanging from the chin) and a head crest made of skin. Fossils have been found in found in Las Hoyas, Cuenca, Spain, including a skull, partial skeleton, and some skin and muscle impressions (which were originally though to be feathers). Pelecanimimus was named by paleontologists Perez-Moreno, Sanz, Buscalloni, Moratalla, Ortega, and Rasskin-Gutman in 1994. The type species is P. polyodon, polyodon meaning "many teeth."

PELONEUSTES Peloneustes was a plesiosaur 10 feet (3 m) long with a big head, streamlined body, long head, and relatively few, not very sharp teeth. Fossilized stomach containing suckers from cephalopods (e.g., squids) have been found. From England and eastern Europe during the late Jurassic period. It was not a dinosaur, but another type of extinct reptile.

PELOROSAURUS (pronounced pe-LOW-roh-SAWR-us) Pelorosaurus (meaning "monstrous lizard") was one of the first sauropod dinosaurs ever discovered. This long-necked plant-eater was about 80 feet (24 m) long. It was a quadruped (it walked on four sturdy legs). It lived during the early Cretaceous period, about 138 to 97 million years ago. Its classification is unsure and the genus status is doubtful; it may have been a Brachiosaurid (related to Brachiosaurus) or a titanosauroid (related to Andesaurus). Pelorosaurus is known from very incomplete skeletons and fossilized skin impressions from the Wealden Formation in England and a from a single forelimb bone found in Fervenca, Portugal. Pelorosaurus was named by the famous fossil hunter Gideon Mantell in 1850. The skin impression showed hexagonal (six-sided) plates that were 9-26 mm across. The type species is P. conybearei.

PELVIS The pelvis (or hip) of dinosaurs is composed of three bones, the Pubis, Ilium, and Ischium. Based on pelvic structure, the British paleontologist H. G. Seeley divided the dinosaurs into the orders Saurischia (or "Lizard-hipped") and Ornithischia (or "Bird-Hipped").

PELYCOSAUR Pelycosaurs (meaning "basin lizards") were the earliest synapsids; they were not dinosaurs. These quadrupeds appeared during the upper Carboniferous and went extinct during the Permian period (before the Triassic period when the dinosaurs evolved). Pelycosaurs began as small, lizard-like animals and evolved into larger, more differentiated types. Some were carnivores, some were herbivores; some had sailbacks like Dimetrodon), some did not. These swamp dwellers with a sprawling gait were likely the ancestors of the therapsids, which led to the mammals. Pelycosaurs are divided in to the suborders Eupelycosauria and Caseasauria.

PENNSYLVANIAN PERIOD The Pennsylvanian Period lasted from 325 to 280 million years ago. During this time, the first reptiles (like Hylonomus) appeared and ferns dominated the warm, swampy landscape.

PENTACERATOPS (pronounced PEN-ta-SER-ah-tops) Pentaceratops (meaning "five-horned-face") was a large ceratopsian dinosaur from the late Cretaceous period, about 75-65 million years ago. This plant-eater had a very large, bony, scalloped, head frill, a snout horn, 2 larger, forwards facing horns above its eyes, and 2 pointy, horn-like cheek bones. Its enormous skull was up to 9.8 feet (3 m) long. Pentaceratops was up to 28 feet (8 m) long. Fossils have been found in New Mexico, USA. It was named by paleontologist Henry F. Osborn in 1923.

PERAMORPHIC Peramorphic organisms develop some adult characteristics at an earlier stage of development than expected. For example, Archaeopteryx has been interpreted as a juvenile Coelophysis with peramorphic development of the arm bones. The large size of some dinosaurs and horn growth in ceratopsians have been explained by peramorphic development or accelerated growth. Peramorph means "beyond shape."

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 EXTINCTION The Permian extinction (also called the Permo-Triassic or P-T extinction) was the largest mass extinction that ever occurred on Earth; it occured ar the end of the Permian period. It may have been caused by powerful Siberian Trap volcanism (caused by plumes of magma erupting). It occurred at end of the Permian period, about 248 million years ago. It in, trilobites went extinct, as did 50% of all animal families, 95% of all marine species, and many trees. Groups that went extinct included: the fusulinid foraminifera, trilobites, rugose and tabulate corals, blastoids, acanthodians, placoderms, and pelycosaurs (like Dimetrodon). Groups that were substantially affected included: bryozoans, brachiopods, ammonoids, sharks, bony fish, crinoids, eurypterids, ostracodes, and echinoderms. This extinction was followed by the Triassic period of the Mesozoic Era.

PERMIAN PERIOD The Permian period (named after the Perm Province in northeast Russia where rocks from this period were first described) is known as "The Age of Amphibians" (280 to 248 million years ago), this is when Pangaea formed and Earth's atmosphere was oxygenated to modern levels. In the early Pemian, labyrinthodonts dominated the land. The Permian ended with the largest mass extinction and was followed by the Mesozoic Era. The Permian was named in 1841 by the geologist Roderick Impey Murchison (1792-1871); he named it for ancient kingdom of Permia (and the modern-day city of Perm by the Ural mountains).

PERMINERALIZATION Permineralization is the process in which minerals are deposited into a bony fossil.

PES Pes is the scientific term for the foot (or foot-like part) of an animal.

PETEINOSAURUS Peteinosaurus (meaning "winged lizard") was an early rhamphorhynchoid pterosaur, a flying reptile that flapped its wings. It lived in swamps and river valleys during the late Triassic period. Peteinosaurus had a wing span of up to 2 feet (60 cm) and weighed up to 3.5 ounces (100 grams). It was an omnivore, eating insects and plants. Peteinosaurus was named by Wild in 1978. Fossils have been found in Europe.

PETRIFICATION Petrification is the process in which an organic tissue turns to stone. The original materials are repaced by minerals.

PETRIFIED WOOD Petrified wood is fossilized wood. Minerals seeped into buried logs, replacing the original tissues with rock.

PHALANGES Phalanges (the singular is phalanx) are the bones in the fingers or toes. A phalanx is a single finger or toe bone.

PHANEROZOIC EON The Phanerozoic (meaning "visible life") is the time in which life forms with skeletons or hard shells existed. It is the period from about 540 million years ago until the present.

PHENETICS Phenetics is a method of attempting to classify biological organisms that does not use genetic or evolutionary information; it was invented by Sokal and Sneath in 1963. In a phenogram, organisms are grouped by superficial overall similarity. Phenetics was abandoned by most scientists in the 1980's because its classifications were arbitrary, mostly useless, and unstable. Paul Ehrlich was a proponent of this system.

PHENOTYPE Phenotype is the set of characters of an organism that are displayed under specific environmental conditions. The phenotype includes the morphological, physiological, behavioral, biochemical, and other characteristics of an organism - traits that are exhibited because of both genes and the environment. (Compare with genotype.)

PHOBETOR Phobetor (meaning "frightening"; Phobetor was a Greek God who personified of the various types of people and beasts in dreams) was a pterosaur that lived during the early Cretaceous period. Phobetor had a wingspan of about 4.9 feet (1.5 m) long. This flying reptile had unusual, upward-curving, narrow jaws in its skull; the tip of the jaws were toothless, but small sharp teeth were behind the tip. Both the snout and top of the head had long, low crests. The skull was 8 inches (20 cm) long. Fossils of this dsungaripterid were found in 1982 in the Zagan Zabsk Formation of western Mongolia. The type species is P. parvus. It was named by Balhurina in 1986. The name "Phobetor" is preoccupied by a fish, so the name of this pterodactyloid will have to change soon.

PHOBOSUCHUS (pronounced FO-bow-SOOK-us) Phobosuchus (meaning "terrible crocodile") is one of the oldest alligator ancestors. This marine reptile was not a dinosaur, but a giant crocodylian. It lived in the seas during the Cretaceous period, about 70 million years ago, when many dinosaurs lived. This giant meat-eater was about 50 ft (15 m) long; its head was 6 feet (1.8 m) long and its teeth were 4 inches (10 cm) long. Phobosuchus may have eaten dinosaurs.

PHORORHACOS Phororhacos is a genus of long-extinct flightless birds that were about 5 feet (1.5 m) long. It had long, sturdy legs, short wings, a large skull, a large, heavy body and a large beak. This carnivore may have eaten small mammals, probably killing them with its beak and legs. It looked like an ostrich with a larger head. It lived during the Oligocene Epoch, about 30 million years ago. Fossils have been found in Patagonia, South America. (Subclass Neornithes, Order Gruiformes)

PHYLETIC GRADUALISM Phyletic gradualism is a theory that addresses the rate of evolutionary changes over time. In this theory, evolutionary changes occur gradually over time, at a relatively slow, even rate. Phyletic gradualism was defined by Eldredge and Gould to contrast with their theory of phyletic equilibria.

PHYLLODON Phyllodon (meaning "leaf tooth") was a plant-eating dinosaur that is only known from its fossilized teeth. This ornithopod lived during the late Jurassic period, about 150 million years ago. Fossil teeth of this ornithischian (lizard-hipped) dinosaur have been found in Portugal, Europe. Phyllodon was named by Thulborn in 1973; this is a dubious genus (due to the small amount of known fossil material). The type species is P. henkeli.

PHYLOGENY Phylogeny is the evolutionary relationship between organisms. The phylogeny of an organism reflects the evolutionary branch that led up to the organism.

PHYLUM (plural - phyla) In classification, a phylum is a group of related or similar organisms. A phylum contains one or more classes. A group of similar phyla forms a Kingdom.

PHYTOSAUR (pronounced FIE-to-SAWR) Phytosaurs (inappropriately meaning "plant lizards") are extinct aquatic reptiles (not dinosaurs but early thecodonts) that resembled crocodiles but they had nostrils near the eyes. They were not that closely related to crocodiles. These quadrupedal, armored carnivores had short legs, a long tail, and many sharp teeth in a long snout. Phytosaurs lived during the late Triassic period about 220 million years ago. They were up to 16 feet (5 m) long. Phytosaurs may have built nests and protected their eggs. Rutiodon, Phytosaurus, and Machaeroprosopus were phytosaurs.

PHYTOSAURUS (pronounced FIE-to-SAWR-us) Phytosaurus (meaning "plant lizards") was an extinct aquatic reptiles (not a dinosaur, but an early thecodont, a phytosaur) that resembled a crocodile but had nostrils near the eyes. Phytosaurus was not that closely related to crocodiles. This quadrupedal, armored carnivore (meat-eater) had many sharp teeth in a long snout, short legs and a long tail, and lived during the late Triassic period about 220 million years ago. It was up to 16 feet (5 m) long. Phytosaurus us known from fragmentary fossilized tooth sockets in a lower jaw (which were mistaken early on for teeth). Phytosaurus was named by Jaeger in 1828.

PIATNITZKYSAURUS (pronounced piat-NYIT-skee-SAWR-us) Piatnitzkysaurus (meaning "[A.] Piatnitzky lizard") was a theropod dinosaur that was 14 ft (4.3 m) long. This meat-eater had a large head, a short neck, small arms, a bulky body and clawed toes; it was similar to Allosaurus. Fossils have been found in Argentina; it is known from 2 fragmentary skeletons. Piatnitzkysaurus was a tetanuran theropod; it lived during the late Triassic period, about 169-163 million years ago. The type species is P. floresi.

PINACOSAURUS (pronounced PIN-ah-co-SAWR-us) Pinacosaurus (meaning "plank lizard") was a medium-sized, armored, beaked, quadrupedal plant-eating dinosaur with a slender build. It dates from the late Cretaceous period, about 85 million to 81 million years ago. This advanced ankylosaur (an ankylosaurid) was about18 feet (5.5 m) long and had a tail club. It had bony spikes along its back and tail, but didn't have armor on its snout. Pinacosaurus had flared nostrils, and four large hoof-covered toes on its front feet and five toes on each of its rear feet. The type species is P. grangeri. Pinacosaurus was named by paleontologist Gilmore in 1933. Over 15 fossils of juveniles have been found in a bone bed in the Gobi desert in Mongolia, China.

PISANOSAURUS (pronounced pe-ZAHN-oh-SAWR-ust) Pisanosaurus (meaning "Pisano's lizard" to honor Juan A. Pisano, an Argentinian paleontologist) was a small, plant-eating dinosaur that lived during the late Triassic period, roughly 220 million years ago. This ornithischian was about 3 ft (1 m) long and walked on two long legs; it had small arms. Only fragmentary fossils have been found (in Argentina, South America). Pisanosaurus was named by Casamiquela in 1967. The type species is P. merti.

PISTOSAURUS (pronounced PIST-oh-SAWR-us) Pistosaurus was a nothosaur, a reptile with flipper-like limbs that lived both on land and in the water. It was about 10 feet (3 m) long with a very long neck, four long, paddle-shaped flippers, a streamlined body, and many sharp, pointed teeth in long jaws. Fossils have been found in France and Germany. It lived during the mid-Triassic period. It was not dinosaur.

PIVETEAUSAURUS (pronounced peev-toh-SAWR-us) Piveteausaurus (meaning "John Piveteau's lizard" - Piveteau was a reknown French paleontologist) was an advanced theropod, a coelurosaurid. It was an intelligent, bipedal meat-eater with bony bumps over its eyes. It was perhaps 36 ft (11 m) long, but this is unsure. A very incomplete fossil was found in northern France. This large predator lived during the mid-Jurassic period, about 160 million years ago. The type species is P. divesensis. Piveteausaurus was named by Taquet and Welles in 1977.

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