Glossary P
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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 is a period of geological time between 286 and 250 million
years ago at the end of the Palaeozoic era. It is separated into two epochs
- the Early Permian (286 to 258 MYA) and the Late Ordovician (258 to 250
MYA).
PERMINERALIZATION
Permineralization is the process in which minerals are deposited into
a bony fossil.
Peteinosaurus
This small omnivorous flying reptile lived in the Late Triassic period.
It inhabited river valleys and swamps and fed on insects, particularly
dragon flies. It was one of the earliest pterosaurs that actually flapped
and had a wing span of up to 60 cm. It weighed up to 100 grams.
Petrification
Petrification is a process of fossilisation in which organic tissue is
replaced by minerals and is thus turned to stone.
Petrified Forest
This important fossil site in St Johns, Arizona, dates back to the Late
Triassic period. It contains fossils of Coelophysis, several Postosuchus,
forty Placerias and two large cynodont teeth. A collection like this helps
palaeontologists reconstruct the ancient ecology of a single location.
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
These were four-legged carnivores that resembled a crocodile and lived
in the Triassic period. They inhabited water courses and fed mostly on
fish and small reptiles. Some grew to very large sizes.
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.