Fossils & Geologic Time, PAL-SIM

Geologic time is the extensive interval of time occupied by the geologic history of Earth. Formal geologic time begins at the start of the Archean Eon (4.0 billion to 2.5 billion years ago) and continues to the present day.
Back To Fossils & Geologic Time Page

Fossils & Geologic Time Encyclopedia Articles By Title

Paleocene-Eocene Thermal Maximum
Paleocene-Eocene Thermal Maximum (PETM), a short interval of maximum temperature lasting approximately 100,000......
Paleogene Period
Paleogene Period, oldest of the three stratigraphic divisions of the Cenozoic Era spanning the interval between......
paleontology
paleontology, scientific study of life of the geologic past that involves the analysis of plant and animal fossils,......
Paleozoic Era
Paleozoic Era, major interval of geologic time that began 538.8 million years ago with the Cambrian explosion,......
palynology
palynology, scientific discipline concerned with the study of plant pollen, spores, and certain microscopic planktonic......
Paradoxides
Paradoxides, genus of trilobites (an extinct group of arthropods) found as fossils in Middle Cambrian rocks of......
Parafusulina
Parafusulina, genus of extinct fusulinid foraminiferans (single-celled animals with a hard, complexly constructed......
Paraschwagerina
Paraschwagerina, genus of extinct fusulinid foraminiferans (protozoans with a relatively large shell readily preservable......
Peach, Charles William
Charles William Peach was an English naturalist and geologist who made valuable contributions to the knowledge......
Peninj mandible
Peninj mandible, an almost perfectly preserved fossil jaw of the hominin (of human lineage) species Paranthropus......
Pennsylvanian Subperiod
Pennsylvanian Subperiod, second major interval of the Carboniferous Period, lasting from 323.2 million to 298.9......
Pentaceratops
Pentaceratops, (genus Pentaceratops), five-horned herbivorous dinosaur found as fossils in North America and possibly......
Pentremites
Pentremites, extinct genus of stemmed, immobile echinoderms (forms related to the starfish) abundant as marine......
Petralona skull
Petralona skull, an ancient human cranium discovered in 1960 in a cave near Thessaloníki, northeastern Greece.......
Petrified Forest National Park
Petrified Forest National Park, desert area containing plant and animal fossils and archaeological sites in eastern......
petrified wood
petrified wood, fossil formed by the invasion of minerals into cavities between and within cells of natural wood,......
Phacops
Phacops, genus of trilobites (an extinct group of aquatic arthropods) found as fossils in Silurian and Devonian......
Phanerozoic Eon
Phanerozoic Eon, the span of geologic time extending about 541 million years from the end of the Proterozoic Eon......
Phenacodus
Phenacodus, extinct genus of mammals known from fossils of the late Paleocene and early Eocene epochs of North......
Phillipsia
Phillipsia, genus of trilobites (an extinct group of aquatic arthropods) uncommonly found as fossils in Carboniferous......
Phoberomys
Phoberomys, extinct rodent genus, the largest rodent ever to have lived, that belongs to the infraorder Caviomorpha,......
Phyllograptus
Phyllograptus, genus of graptolites, an extinct group of small colonial marine animals related to the primitive......
phytosaur
phytosaur, heavily armoured semiaquatic reptiles found as fossils from the Late Triassic Period (about 229 million......
Piltdown man
Piltdown man, (Eoanthropus dawsoni), proposed species of extinct hominin (member of the human lineage) whose fossil......
placoderm
placoderm, any member of an extinct group (Placodermi) of primitive jawed fishes known only from fossil remains.......
Plateosaurus
Plateosaurus, (genus Plateosaurus), dinosaurs known from extensive fossil material found in Europe dating to the......
Platyceras
Platyceras, genus of extinct gastropods (snails) that occurs as fossils in rocks of Silurian to Permian age (about......
Platycrinites
Platycrinites, genus of extinct crinoids, or sea lilies, especially characteristic as fossils of Early Carboniferous......
Platystrophia
Platystrophia, genus of extinct brachiopods (lamp shells) occurring as fossils in marine rocks of the Middle Ordovician......
Plectoceras
Plectoceras, extinct genus of small marine nautiloid cephalopods, forms related to the modern pearly nautilus,......
Pleistocene Epoch
Pleistocene Epoch, earlier and major of the two epochs that constitute the Quaternary Period of Earth’s history,......
plesiosaur
plesiosaur, (clade Plesiosauria), any of a group of long-necked marine reptiles found as fossils from the late......
Pleuromeia
Pleuromeia, genus of extinct lycopsid plants from the Triassic Period (about 251 million to 200 million years ago)......
Pliocene Epoch
Pliocene Epoch, second of two major worldwide divisions of the Neogene Period, spanning the interval from about......
Pliohippus
Pliohippus, extinct genus of horses that inhabited North America during the Pliocene Epoch (5.3–2.6 million years......
pliosaur
pliosaur, a group of large carnivorous marine reptiles characterized by massive heads, short necks, and streamlined......
Podokesaurus
Podokesaurus, (Podokesaurus holyokensis), small carnivorous North American dinosaur found as a single specimen......
polychaete hypothesis
polychaete hypothesis, theory that conodonts (minute toothlike structures found as fossils in marine rocks) are......
polygnathiform
polygnathiform, conodont, or small toothlike fossil of uncertain relationship found widely in ancient marine rocks,......
potassium-argon dating
potassium-argon dating, method of determining the time of origin of rocks by measuring the ratio of radioactive......
Pound Quartzite
Pound Quartzite, formation of Precambrian rocks (dating from 3.96 billion to 540 million years ago) in the region......
Prasopora
Prasopora, extinct genus of bryozoans, small colonial animals that formed mosslike or encrusting growths, especially......
prefern
prefern, any of a group of extinct plants considered transitional between the first land plants, the psilophytes,......
Pridoli Series
Pridoli Series, uppermost of four main divisions of the Silurian System, representing those rocks deposited worldwide......
proconodontid
proconodontid, a small toothlike structure found in marine rocks formed over a long span of geologic time, that......
protactinium-231–thorium-230 dating
protactinium-231–thorium-230 dating, method of age determination that makes use of the quantities of certain protactinium......
Proterozoic Eon
Proterozoic Eon, the younger of the two divisions of Precambrian time, the older being the Archean Eon. The Proterozoic......
Protoceratops
Protoceratops, (genus Protoceratops), ceratopsian dinosaur found as fossils in the Gobi Desert from 80-million-year-old......
Pseudoschwagerina
Pseudoschwagerina, extinct genus of fusulinid foraminiferans (single-celled animals with hard shells preservable......
Psittacosaurus
Psittacosaurus, (genus Psittacosaurus), primitive member of the horned dinosaurs (Ceratopsia) found as fossils......
Pteranodon
Pteranodon, (genus Pteranodon), flying reptile (pterosaur) found as fossils in North American deposits dating from......
Pteraspis
Pteraspis, genus of extinct jawless fishlike vertebrates found as fossils in Early Devonian rocks (those 398 million......
pterodactyl
pterodactyl, informal term for a subgroup of flying reptiles (Pterosauria) known from the Late Jurassic through......
pterosaur
pterosaur, any of the flying reptiles that flourished during all periods (Triassic, Jurassic, and Cretaceous) of......
Ptilodus
Ptilodus, extinct genus of mammals found as fossils in deposits dated to the Paleocene Epoch (65.5–55.8 million......
Pycnodontiformes
Pycnodontiformes, order of extinct fishes of the class Actinopterygii, containing the genus Pycnodus, common in......
Pääbo, Svante
Svante Pääbo is a Swedish evolutionary geneticist who specialized in the study of DNA from ancient specimens and......
Qafzeh
Qafzeh, paleoanthropological site south of Nazareth, Israel, where some of the oldest remains of modern humans......
Quaternary
Quaternary, in the geologic history of Earth, a unit of time within the Cenozoic Era, beginning 2,588,000 years......
Quenstedt, Friedrich August
Friedrich August Quenstedt was a German mineralogist and paleontologist. Quenstedt studied at the University of......
Quetzalcoatlus
Quetzalcoatlus, genus made up of two species of giant pterosaurs classified in the family Azhdarchidae, which contains......
radiation-damage dating
radiation-damage dating, method of age determination that makes use of the damage to crystals and the radiation......
Ramapithecus
Ramapithecus, fossil primate dating from the Middle and Late Miocene epochs (about 16.6 million to 5.3 million......
Rensselaeria
Rensselaeria, genus of extinct brachiopods (lamp shells) found as fossils in Lower Devonian marine rocks (387 to......
Resserella
Resserella, extinct genus of brachiopods (lamp shells) that occurs as fossils in marine rocks of Middle Ordovician......
Rhamphorhynchus
Rhamphorhynchus, (genus Rhamphorhynchus), flying reptile (pterosaurs) found as fossils from the Late Jurassic Period......
rhenium–osmium dating
rhenium–osmium dating, method of determining the age of the important ore mineral molybdenite; the method is based......
Rhipidistia
Rhipidistia, extinct group of lobe-finned bony fishes of the order Crossopterygii that included the ancestors of......
Rhynchotrema
Rhynchotrema, extinct genus of brachiopods, or lamp shells, found as fossils in Middle and Late Ordovician rocks......
Rhynchotreta
Rhynchotreta, extinct genus of brachiopods (lamp shells) commonly found as fossils in Silurian marine rocks (between......
Rhynie plant
Rhynie plant, rootless, leafless, spore-bearing plant preserved in the Rhynie Chert, a mineral deposit that has......
Riversleigh fossils
Riversleigh fossils, any of numerous assemblages of fossils found at Riversleigh Station, in northwestern Queensland,......
Roadian Stage
Roadian Stage, first of the three stages of the Middle Permian (Guadalupian) Series, made up of all rocks deposited......
Romer, Alfred Sherwood
Alfred Sherwood Romer was a U.S. paleontologist widely known for his concepts of evolutionary history of vertebrate......
rubidium-strontium dating
rubidium-strontium dating, method of estimating the age of rocks, minerals, and meteorites from measurements of......
sabre-toothed cat
sabre-toothed cat, any of the extinct catlike carnivores belonging to either the extinct family Nimravidae or the......
Saccopastore skulls
Saccopastore skulls, two Neanderthal fossils found in 1929 and 1935 in a river deposit on the bank of a small tributary......
Saint-Césaire
Saint-Césaire, paleoanthropological site in southwestern France where in 1979 the remains of a young adult male......
Sakmarian Stage
Sakmarian Stage, second of the four stages of the Early Permian (Cisuralian) Epoch, encompassing all rocks deposited......
Sanmiguelia
Sanmiguelia, genus of fossil plants based upon impressions of palmlike leaves from the Triassic Period (251 to......
saurischian
saurischian, any member of one of the two major lineages of dinosaurs, including birds and all dinosaurs more closely......
sauropod
sauropod, any member of the dinosaur subgroup Sauropoda, marked by large size, a long neck and tail, a four-legged......
sauropterygian
sauropterygian, any of the aquatic reptiles found as fossils from the Mesozoic Era (251 million to 66 million years......
Scaphites
Scaphites, extinct genus of cephalopods (animals related to the modern octopus, squid, and nautilus) found as fossils......
Schindewolf, Otto Heinrich
Otto Heinrich Schindewolf was a German paleontologist, known for his research on corals and cephalopods. Schindewolf......
Schizodus
Schizodus, extinct genus of small mollusks found as fossils in rocks from the Devonian to the Permian Period (416......
Schuchert, Charles
Charles Schuchert was an American paleontologist who was a leader in the development of paleogeography, the study......
Schwagerina
Schwagerina, extinct genus of fusulinid foraminiferans, small, single-celled protozoans related to the modern amoeba......
Scott, Dunkinfield Henry
Dunkinfield Henry Scott was an English paleobotanist and leading authority of his time on the structure of fossil......
Scutellosaurus
Scutellosaurus, genus of small ornithischian dinosaurs from the Early Jurassic Period (roughly 200 million to 176......
seed fern
seed fern, loose confederation of seed plants from the Carboniferous and Permian periods (about 360 to 250 million......
Sereno, Paul
Paul Sereno is an American paleontologist who discovered several notable dinosaur species while on field expeditions......
Serpukhovian Stage
Serpukhovian Stage, third of three internationally defined stages of the Mississippian Subsystem of the Carboniferous......
Seymouria
Seymouria, extinct genus of terrestrial tetrapod found as fossils in Permian rocks (251 million to 299 million......
Shanidar
Shanidar, site of paleoanthropological excavations in the Zagros Mountains of Iraqi Kurdistan. Two clusters of......
Sigillaria
Sigillaria, extinct genus of tree-sized lycopsids from the Carboniferous Period (about 360 to 300 million years......
Simocetus
Simocetus, dolphinlike toothed whale (or odontocete) from the late Oligocene (28 million to 23 million years ago)......

Fossils & Geologic Time Encyclopedia Articles By Title