ZoomDinosaurs.com Dinosaur and Paleontology Dictionary

PACHYCEPHALOSAURIDS (pronounced pack-ih-SEF-ah-low-SAWR-ids) Pachycephalosaurs (meaning "thick head lizards") were plant-eating, thick-headed, short-armed, bipedal ornithischian dinosaurs from the late Cretaceous period. Pachycephalosaurus, Homalocephale, and Stegoceras were pachycephalosaurs. They are sometimes called bone-headed dinosaurs.

PACHYCEPHALOSAURUS (pronounced pack-ih-SEF-ah-low-SAWR-us) Pachycephalosaurus (meaning "thick head lizard") was a plant-eating, dome-headed dinosaur 15 feet (4.6 m) long; it had a skull up to 10 inches thick (25 cm). It was named by Brown and Schlaikjer in 1943. The type species is P. wyomingensis.

PACHYRHINOSAURUS (pronounced pack-ee-RINE-oh-SAWR-us) Pachyrhinosaurus (meaning "thick-nosed lizard") was a plant-eating, short-frilled ceratopsian dinosaur 18 to 23 feet (5.5 to 7 m) long. Pachyrhinosaurus may or may not have a snout horn - it had a large bony bump on its nose (which may have had a horn growing on it). It also had many small horns on the middle of its frill. It lived during the late Cretaceous period, about 72 to 68 million years ago. Fossils (12 partial skulls and some assorted bones) have been found in Alberta, Canada, and Alaska, USA. The type species is P. canadensis. Pachyrhinosaurus was named by paleontologist Charles M. Sternberg in 1950.

PACHYRUKHOS Pachyrukhos was an early mammal that filled a niche similar to the one that modern-day rabbits inhabit. Pachyrukhos was about 1 foot (30 cm) long. It had large ears and eyes, a pointed snout, a short tail, short front limbs, and well-developed hind legs. It probably moved by hopping. This mammal was probably nocturnal (given its large eyes and ears). This herbivore (plant-eater) ate nuts and tough plant material. It lived from the late Oligocene to the middle Miocene. Fossils have been found in South America.

PAEDOMORPHIC Paedomorphic organisms retain some juvenile (or larval) characteristics during thier adult stage. An example of a paedomophic species is Cope's Giant Salamander; although it apprears to be a juvenile throughout its life, it can successfully reproduce. Monoclonius is a plant-eating dinosaur that may have paedomorphic (juvenile-like) features.

PAKICETUS Pakicetus is an early fossil whale with a pointed snout. It was about 6 ft (1.8 m) long. It was found in Pakistan and dates from the early Eocene (about 54 million years ago). Pakicetus had pointed teeth like Mesonychid and a pinched brain case like Ambulocetus. It had a water-adapted inner ear but still had four limbs (probably paddle-shaped) and may have spent part of its life on land. Pakicetus had nostrils located at the front of head, and no blowhole.

PALAEOPTERYX (pronounced PAY-lee-OP-ter-iks) Palaeopteryx (meaning "ancient wing") was a meat-eater from the late Jurassic period. It was either a theropod dinosaur (a dromaeosaurid) or a bird; its classification is in dispute. Palaeopteryx was redescribed by Jensen and Padian in 1989 as belonging to Deinonychus. Fossils have been found in North America. Palaeopteryx named by Jensen in 1981. This is dubious genus.

PALAEOSCINCUS (pronounced PAY-lee-oh-SKINK-us) Palaeoscincus (meaning "ancient skink") was an armored, plant-eating dinosaur from the late Cretaceous period, 83-73 million years ago. This nodosaurid ankylosaur was about 18 ft (5.5 m) long. It is known from a single tooth found in Montana, USA. It was named by Leidy in 1856. The type species is P. costatus. Palaeoscincus is a doubtful species; it may be the same as Edmontonia or Panoplosaurus.

PALEOANTHROPOLOGY Paleoanthropology (meaning "study of ancient man") is the study of the origins and the ancestors of human beingsby examining fossil remains (and other ancient evidence). A paleoanthropologist studies paleoanthropology.

PALEOBOTANY Paleobotany is the branch of botany that studies the plants that existed in former geologic periods, chiefly by studying fossils.

PALEOCLIMATOLOGY Paleoclimatology (meaning "study of ancient climates") is the study of the climates during ancient times.

PALEOGEOGRAPHY Paleography is the study of the Earth's geographic features during ancient times.

PALEOGEOLOGY Paleogeology is the study of the Earth;s geologic conditions during ancient times.

PALEOGEOPHYSICS Paleogeophysics is the study of ancient geophysical conditions.

PALEOGNATHAE The Palaeognathae (meaning "ancient jaw") are the largest living birds, and are mostly flightless (but not all flightless are Palaeognathae, and not all Palaeognathae are large). They include the ostrich, emu, kiwi, etc. Palaeognathae are generally fast runners and use kicking as a primary defense. Palaeognaths probably evolved from early Cenozoic flying ancestors. They are grouped together taxonomically based on palate (jaw) structure. (Compare to Neognathae.)

PALEOMAGNETISM Paleomagnetism is the magnetism that remains in volcanic rock from the time it solidified from magma.

PALEONEUROLOGY Paleoneuroloy is the study of fossils brains (from brain casts, called endocasts).

PALEONTOLOGY Paleontology is the branch of biology that studies the forms of life that existed in former geologic periods, chiefly by studying fossils. "Paleo" means old or ancient. "Ontology" is the study of existence ("onto-" means existence, "-logy" is the study of something).

PALEONTOLOGIST A paleontologist is a scientist who studies paleontology, the forms of life that existed in former geologic periods, chiefly by studying fossils. "Paleo" means old or ancient. "Ontology" is the study of existence ("onto-" means existence, "-logy" is the study of something). This "-ist" at the end means a person who is involved in the field.

PALEOZOIC ERA The Paleozoic Era (540 to 248 million years ago) saw an explosion of new life forms. The Paleozoic (meaning "ancient life") ended with the largest mass extinction in geologic history and was followed by the Mesozoic Era. It is divided into the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian periods. It was followed by the Mesozoic Era, the time of the dinosaurs.

PALEOZOOLOGY Paleozoogy (meaning "study of ancient life") is the branch of paleontology that studies fossil animals.

PALPEBRAL The palpebral is a small bone in the eye socket (in ornithischian dinosaurs and some others).

PALYNOLOGY Palynology is the study of pollen and spores, from both living and fossil plants and protists.

PANGAEA (pronounced pan-GEE-ah) Pangaea was a supercontinent consisting of all of Earth's land masses. It existed during the Permian through the Jurassic period. It began breaking up during the Jurassic, forming the continents Gondwanaland and Laurasia.

PANOPLOSAURUS (pronounced PAN-oh-ploh-SAWR-us) Panoplosaurus (meaning "totally armored lizard") was an armored, plant-eating dinosaur from the late Cretaceous period, 76-73 million years ago. This nodosaurid ankylosaur (no tail club) was about 23 ft (7 m) long and weighed about 3.5 tons. Fossils have been found in found in Alberta, Canada and Montana, USA . It was named in 1919 by Canadian paleontologist L. Lambe, from a specimen found in 1917 in the Judith River Formation in Alberta, Canada. The type species is P. mirus.

PANTHALASSA (pronounced pan-tha-LASS-ah) Panthalassa (meaning "All seas") was the super-ocean that existed on Earth during the time of the super-continent Pangaea. Panthalassa existed during the Permian through the Jurassic period, when Pangaea began to break up; the Tethys sea formed between the northern and southern parts of pangaea as they drifted apart.

PARACERATHERIUM Paraceratherium (similar to Indricotherium) is a large, extinct, hornless rhinoceros. It was one of the largest land mammals. Adults were about 26 feet (8 m) long, 18 feet (5.5 m) tall, and weighed about 15-20 tons. The skull was 4.25 feet (1.3 m) long. This herbivore ate leaves and twigs from the tops of trees. It had four teeth; two tusk-like front teeth in the top jaw, pointing down and two on the bottom pointing forwards. This extinct ungulate (hoofed mammal) had three toes on each foot and lived from the Oligocene to the early Miocene (roughly 30 million years ago) in central Asia (Pakistan, Mongolia and China). Paraceratherium was first found by English paleontologist C. Forster Cooper in Pakistan in 1910. Classification: Order Perissodactyla (odd-toed ungulates), Family Hyrachyidae (odd-toed ungulates between tapirs and rhinos)..

PARALITITAN Paralititan (meaning "tidal Titan") was a huge titanosaurid sauropod that lived during the middle Cretaceous period, about 100 million years ago. This plant-eating dinosaur had a long neck, small head, bulky body, and long tail. It was about 78-100 ft long (24-30 m long) and weighed perhaps 70 tonnes. Fossils were found in Bahariya Oasis, Egypt. Paralititan was named by Joshua B. Smith, Lamanna, Lacovara, Dodson, Smith, Poole, Giegengack and Attia in 2001. The type species is P. stromeri (2001, named to honor Ernst Stromer von Reichenbach, a German paleontologist and geologist who found dinosaurs in this area in the early 1900's).

PARAPATRIC SPECIATION Paripatric speciation (the formation of new species) occurs when a population enters a new habitat or niche within the same geographical area of the parent species, but becomes reproductively isolated from the parent species. Compare with allopatric speciation and sympatry.

PARAPATRY Paripatry means occupying overlapping geographic locations. Compare with allopatry and sympatry.

PARAPHYLETIC GROUP A paraphyletic group (also called a grade) consists of a common ancestor and some, but not all, of its descendants. These are incomplete groups based primarily on physical characteristics rather than directly on evolutionary relationships. An example of a paraphyletic group is the dinosaurs (without including the birds).

PARA-SACRAL SPINES Para-sacral spines are bony spikes that extend from the hip area in stegosaurs (like Stegosaurus and Kentrosaurus).

PARASAUROLOPHUS (pronounced PAR-ah-saw-ROL-oh-fus) Parasaurolophus was a long-crested, duck-billed dinosaur from the late Cretaceous period. This beaked plant-eater was about 33 feet (10 m) long. The type species is P. walkeri; it was named by Parks in 1922.

PARASITE A parasite is an organism (a plant or animal) that lives on another organism (the host), obtaining nutrition from it and sapping or killing the host.

PARASITISM Parasitism is arelationship between two organisms in which one organism benefits at the other organism's expense. Lice are an example of a parasite that affects many animals; termites are a parasite that are destructive to many trees. Parasitism is a type of symbiosis.

PARATYPE A paratype is all of the specimens of the type series of a species or subspecies other than the holotype.

PAREIASAUR Pareiasaurs are close relatices of turtles (they may be the ancestors of turtles, but many scientists think that procolophonids are the turtles' ancestors). These herbivores (plant-eaters) had polygonal bony scales (scutes) on their body that acted as armor (these scutes may have evolved into the turtle's shell). They had iguana-like teeth, a bulky body, four short legs, a box-like skull, and a short, pointed tail. They include the biggest terrestrial anapsids that ever lived; they were up to about 7.5 ft (2.5 m long). These reptiles lived during the late Permian (about 260 million years ago) and probably went extinct during the Permian mass extinction. These amniotes were early anapsids. Fossils have been found in Europe, Asia, and Africa. Some Pareiasaurs include Bradysaurus, Scutosaurus, and Anthodon.

PARKS, WILLIAM A. William Arthur Parks (1868-1939) was a Canadian paleontologist who described Arrhinoceratops (1925), Dyoplosaurus (1924), Lambeosaurus (1923), and Parasaurolophus (1923). Parksosaurus was named by paleontologist Chas. M. Sternberg in 1937 to honor Parks.

PARKSOSAURUS (pronounced PARK-soh-SAWR-us) Parksosaurus (meaning "[William Arthur Parks (1868-1939), a Canadian paleontologist] Parks' lizard") was a small, plant-eating dinosaur from the late Cretaceous period, about 68-65 million years ago. This biped was about 7 ft (2 m) long, weighing roughly 150 pounds (70 kg). It had a long tail, strong arms, a long neck, and short toes. Parksosaurus had a small head with wide jaws and unique teeth (they had low, rounded ridges). Incomplete fossils of this hypsilophodontid ornithopod has been found in Alberta, Canada and Montana, USA. Parksosaurus was named by paleontologist Chas. M. Sternberg in 1937. The type species is P. warrenae.

PARONYCHODON (pronounced parr-oh-NYE-co-don) Paronychodon (meaning "near claw tooth") was a small, meat-eating dinosaur that lived during the late Cretaceous period, about 73-65 million years ago. This advanced theropod is known only from non-serrated teeth found in Montana, New Mexico, and Wyoming, USA. Paronychodon was named by paleontologist E. D. Cope in 1876; the type species is P. lacustris. Paronychodon is a dubious genus since only fossils teeth have been found; it may be the same as Troodon or another troodontid.

PARROSAURUS (pronounced PARR-oh-SAWR-us) Parrosaurus (meaning "Parr lizard, honoring Albert Eide Parr, an American zoologist") is an invalid name for Hypsibema, an ornithopod dinosaur (probably a duckbill, but only a few bones have been found) from the late Cretaceous period, about 83-73 million years ago. Parrosaurus missouriensis was named by paleontologist Charles W. Gilmore in 1945.

PARSIMONY Parsimony is the scientific idea that the simplest explanation of a phenomenon is the best one.

PATAGONYKUS (pronounced pat-ah-GONE-eh-kus) Patagonykus (meaning "Patagonia claw") was a lightly-built meat-eater with a single, clawed finger on each hand. It was about 6.5 ft (2 m) long. It had long legs, a long tail, and short arms. Patagonykus lived during the late Cretaceous period, about 90 million years ago. Patagonykus was either a bird-like dinosaur (an advanced theropod, or a primitive bird; it possessed qualities of both groups of animals, and there is much scientific debate over which it is. Patagonykus was similar to Mononykus. Fossils were found in Patagonia, a region of southern Argentina. The type species is P. puertai. Patagonykus was named by paleontologist F. Novas in 1996.

PATAGOSAURUS (pronounced PAT-a-go-SAWR-us) Patagosaurus (meaning "Patagonian or big-footed lizard") was a large, quadrupedal, plant-eating dinosaur from the middle Jurassic period, about 169-163 million yeas ago. This cetiosaurid, a primitive sauropod, was about 65 feet (20 m) long; it had a small head, a long neck, and a long tail. Patagosaurus was found in Patagonia, in southern Argentina. Patagosaurus is similar to the European dinosaur Cetiosaurus, and lends support to the theory of continental drift, and South America and Europe being connected during the Jurassic period. Patagosaurus was named by Bonaparte in 1979. The type species is P. fariasi.

PAWPAWSAURUS (pronounced paw-paw-SAWR-us) Pawpawsaurus (meaning "paw-paw formation lizard") was a large, armored, quadrupedal, plant-eating dinosaur from the middle Cretaceous period, about 97 million yeas ago. This nodosaurid ankylosaur had bony eyelids and armor over most of its body (it did not have a tail club). Incomplete fossils have been found in Tarrant County, Texas. Pawpawsaurus was named by Yuong-Nam Lee in 1996. The type species is P. campbelli (C. Campbell discovered the fossil).

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