Fossils & Geologic Time, LAR-PAL

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.
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Fossils & Geologic Time Encyclopedia Articles By Title

Lartet, Édouard
Édouard Lartet was a French geologist, archaeologist, and a principal founder of paleontology. He is credited chiefly......
Le Moustier
Le Moustier, paleoanthropological and archaeological site in the Dordogne region of southwestern France that has......
lead-210 dating
lead-210 dating, method of age determination that makes use of the ratio of the radioactive lead isotope lead-210......
Leakey, Louis
Louis Leakey was a Kenyan archaeologist and anthropologist, a member of the distinguished Leakey family of scholars......
Lebachia
Lebachia, a genus of extinct cone-bearing plants known from fossils of the Late Carboniferous and Early Permian......
Leidy, Joseph
Joseph Leidy was a zoologist, one of the most distinguished and versatile scientists in the United States, who......
Lepidodendron
Lepidodendron, extinct genus of tree-sized lycopsid plants that lived during the Carboniferous Period (about 359......
Leptaena
Leptaena, genus of extinct brachiopods (lamp shells) commonly found as fossils in Ordovician to Lower Carboniferous......
Leptodesma
Leptodesma, extinct genus of pelecypods (clams) found as fossils in Silurian to Lower Carboniferous rocks (between......
Leptodus
Leptodus, extinct genus of articulate brachiopods, or lamp shells, of the Permian Period (299 million to 251 million......
Leptolepis
Leptolepis, genus of marine fishes very closely related to the first teleosts, the dominant group of fishes in......
Limnoscelis
Limnoscelis, extinct genus of tetrapod that appeared very close to the origin of amniotes (mammals, birds, or reptiles).......
Linoproductus
Linoproductus, genus of extinct articulate brachiopods (lamp shells) found throughout the midcontinent region of......
Lipalian interval
Lipalian interval, in geology, time span suggested in an attempt to explain the sudden appearance of abundant life......
litoptern
litoptern, (order Litopterna), any of various extinct hoofed mammals that first appeared in the Paleocene Epoch......
Lituites
Lituites, genus of extinct cephalopods (primitive animals related to the modern pearly nautilus) found as fossils......
Llanocetus denticrenatus
Llanocetus denticrenatus, one of the earliest known baleen whales, sole member of the family Llanocetidae, suborder......
Lluc
Lluc, (Anoiapithecus brevirostris), nickname for the nearly complete upper and lower jaws and much of the associated......
Lonsdale, William
William Lonsdale was an English geologist and paleontologist whose studies of fossil corals suggested the existence......
lophophore hypothesis
lophophore hypothesis, viewpoint that conodonts, small toothlike structures found as fossils in marine rocks over......
Lophophyllum
Lophophyllum, extinct genus of solitary marine corals found as fossils especially characteristic of the Late Carboniferous......
Lophospira
Lophospira, genus of extinct gastropods (snails) found as fossils in marine rocks of Ordovician to Devonian age......
Loxonema
Loxonema, genus of extinct gastropods (snails) found as fossils in rocks of Ordovician to Early Carboniferous age......
Lucy
Lucy, nickname for a remarkably complete (40 percent intact) hominin skeleton found by American paleoanthropologist......
Ludfordian Stage
Ludfordian Stage, second of two stages of the Ludlow Series, made up of all rocks deposited during the Ludfordian......
Ludlow Series
Ludlow Series, the third of four main divisions (in ascending order) making up the Silurian System; it represents......
Lystrosaurus
Lystrosaurus, extinct genus of about seven species of medium-sized heavily built animals that lived from the middle......
Maclurites
Maclurites, extinct genus of Ordovician gastropods (snails) found as fossils and useful for stratigraphic correlations......
Maiasaura
Maiasaura, (genus Maiasaura), duck-billed dinosaurs (hadrosaurs) found as fossils from the Late Cretaceous Period......
mammoth
mammoth, (genus Mammuthus), any member of an extinct group of elephants found as fossils in Pleistocene deposits......
Mantell, Gideon Algernon
Gideon Algernon Mantell was a British physician, geologist, and paleontologist, who discovered four of the five......
Marasuchus
Marasuchus, genus of archosaurian reptiles that inhabited part of present-day South America during the Ladinian......
Marsh, Othniel Charles
Othniel Charles Marsh was an American paleontologist who made extensive scientific explorations of the western......
mastodon
mastodon, (genus Mammut), any of several extinct elephantine mammals (family Mammutidae, genus Mammut ) that first......
Matthew, William Diller
William Diller Matthew was a Canadian-American paleontologist who was an important contributor to modern knowledge......
Mauer
Mauer, Pleistocene locality on the Neckar River of Germany and the name of a Pleistocene deposit, the Mauer Sands......
medieval warm period
medieval warm period (MWP), brief climatic interval that is hypothesized to have occurred from approximately 900......
megalodon
megalodon, (Carcharocles megalodon), member of an extinct species of megatooth shark (Otodontidae) that is considered......
Megalosaurus
Megalosaurus, (genus Megalosaurus), carnivorous dinosaur and the subject of the first scientific description of......
Megatherium
Megatherium, largest of the ground sloths, an extinct group of mammals belonging to a group containing sloths,......
Merychippus
Merychippus, extinct genus of early horses, found as fossils in deposits from the Middle and Late Miocene Epoch......
Mesohippus
Mesohippus, genus of extinct early and middle Oligocene horses (the Oligocene Epoch occurred from 33.9 to 23 million......
Mesosaurus
Mesosaurus, (genus Mesosaurus), early aquatic relative of reptiles, found as fossils from the Early Permian Period......
Mesozoic Era
Mesozoic Era, second of Earth’s three major geologic eras of Phanerozoic time. Its name is derived from the Greek......
Miacis
Miacis, genus of extinct carnivores found as fossils in deposits of the late Paleocene Epoch (65.5–55.8 million......
Miocene Epoch
Miocene Epoch, earliest major worldwide division of the Neogene Period (23 million years to 2.6 million years ago)......
Miohippus
Miohippus, genus of extinct horses that originated in North America during the Late Eocene Epoch (37.2–33.9 million......
Mississippian Subperiod
Mississippian Subperiod, first major subdivision of the Carboniferous Period, lasting from 358.9 to 323.2 million......
Modiolopsis
Modiolopsis, extinct genus of pelecypods (clams) found as fossils in Ordovician rocks (about 488 million to 444......
Moeritherium
Moeritherium, extinct genus of primitive mammals that represent a very early stage in the evolution of elephants.......
Monograptus
Monograptus, extinct genus of graptolites (small aquatic colonial animals related to primitive chordates) found......
Moore, Raymond Cecil
Raymond Cecil Moore was an American paleontologist known for his work on Paleozoic crinoids, bryozoans, and corals......
Morganucodon
Morganucodon, extinct genus of tiny mammals known from fossils dated to the Triassic-Jurassic boundary (approximately......
Moropus
Moropus, extinct genus of the chalicotheres, a group of very unusual perissodactyls (“odd-toed” ungulates) related......
Morrison Formation
Morrison Formation, series of sedimentary rocks deposited during the Jurassic Period in western North America,......
mosasaur
mosasaur, (family Mosasauridae), extinct group of aquatic lizards that attained a high degree of adaptation to......
Moschops
Moschops, extinct genus of mammal-like reptiles (Therapsida) found as fossils in rocks of Permian age (299 million......
Moscovian Stage
Moscovian Stage, second of four internationally defined stages of the Pennsylvanian Subsystem of the Carboniferous......
Mucrospirifer
Mucrospirifer, genus of extinct brachiopods (lamp shells) found as fossils in Middle and Upper Devonian marine......
multituberculate
multituberculate, any member of an extinct group of small, superficially rodentlike mammals that existed from about......
Mylodon
Mylodon, extinct genus of ground sloth found as fossils in South American deposits of the Pleistocene Epoch (2.6......
Myophoria
Myophoria, genus of extinct clams found as fossils in Triassic rocks. It is readily identified by its distinctive......
Müller, Sophus Otto
Sophus Otto Müller was a Danish archaeologist who, during the late 19th century, discovered the first of the Neolithic......
Neanderthal
Neanderthal, (Homo neanderthalensis, Homo sapiens neanderthalensis), member of a group of archaic humans who emerged......
Neogene Period
Neogene Period, the second of three divisions of the Cenozoic Era. The Neogene Period encompasses the interval......
neoprioniodiform
neoprioniodiform, conodont, or small toothlike phosphatic fossil of uncertain affinity, that is characterized by......
Neospirifer
Neospirifer, genus of extinct brachiopods (lamp shells) found as fossils in Late Carboniferous to Permian marine......
Nodosaurus
Nodosaurus, (genus Nodosaurus), armoured dinosaurs found as fossils in North America dating from 95 million to......
Notharctus
Notharctus, extinct genus of small primates (family Adapidae) that shares many similarities with modern lemurs,......
Nothosaurus
Nothosaurus, (genus Nothosaurus), marine reptiles found as fossils from the Triassic Period (251 million to 200......
Notoungulata
Notoungulata, extinct group of hoofed mammals found as fossils, mostly in South America, although the oldest forms......
nummulite
nummulite, any of the thousands of extinct species of relatively large, lens-shaped foraminifers (single-celled......
Obolus
Obolus, genus of extinct brachiopod, or lamp shell, of the Cambrian Period (from 542 million to 488 million years......
obsidian–hydration–rind dating
obsidian–hydration–rind dating, method of age determination of obsidian (black volcanic glass) that makes use of......
odontolite
odontolite, fossil bone or tooth that consists of the phosphate mineral apatite (q.v.) coloured blue by vivianite.......
Old Red Sandstone
Old Red Sandstone, thick sequence of Devonian rocks (formed from 416 million to 359.2 million years ago) that are......
Olenellus
Olenellus, genus of trilobites (extinct arthropods) common in but restricted to Early Cambrian rocks (542 million......
Oligocene Epoch
Oligocene Epoch, third and last major worldwide division of the Paleogene Period (65.5 million to 23 million years......
Onverwacht series
Onverwacht series, division of Archean rocks (the Archean Eon lasted from 3.96 to 2.5 billion years ago) in the......
Oppel, Albert
Albert Oppel was a German geologist and paleontologist, who was one of the most important early stratigraphers.......
Orbigny, Alcide Dessalines d’
Alcide Dessalines d’ Orbigny was the founder of the science of micropaleontology. During eight years of travel......
oreodont
oreodont, any member of a diverse group of extinct herbivorous North American artiodactyls (even-toed ungulates)......
Oreopithecus
Oreopithecus, extinct genus of primates found as fossils in Late Miocene deposits in East Africa and Early Pliocene......
ornithischian
ornithischian, any member of the large taxonomic group of herbivorous dinosaurs comprising Triceratops and all......
Ornitholestes
Ornitholestes, (genus Ornitholestes), small, lightly built carnivorous dinosaur found as fossils from the Late......
Ornithomimus
Ornithomimus, (genus Ornithomimus), ostrichlike feathered dinosaurs found as fossils in Mongolian, European, and......
ornithopod
ornithopod, any member of the group of ornithischian dinosaurs characterized by a two-legged (bipedal) stance,......
Osborn, Henry Fairfield
Henry Fairfield Osborn was an American paleontologist, eugenicist, and museum administrator who greatly influenced......
Osteolepis
Osteolepis, extinct genus of lobe-finned fishes from the Late Devonian; Osteolepiformes is a variation of this......
Ostrom, John
John Ostrom was an American paleontologist who popularized the theory that many species of dinosaurs were warm-blooded......
Oviraptor
Oviraptor, (genus Oviraptor), small, lightly built predatory or omnivorous dinosaur that brooded its eggs in a......
Owen, Richard
Richard Owen was a British anatomist and paleontologist who is remembered for his contributions to the study of......
ozarkodiniform
ozarkodiniform, conodont, or small fossil that is toothlike in form and structure, that has a prominent, centrally......
Pachycephalosaurus
Pachycephalosaurus, genus of large and unusual dinosaurs found as fossils in deposits of North America dating to......
Pachyrhinosaurus
Pachyrhinosaurus, genus of horned ceratopsid dinosaurs that roamed northwestern North America from 71 million to......
Pakicetus
Pakicetus, extinct genus of early cetacean mammals known from fossils discovered in 48.5-million-year-old river......
Palaeospondylus
Palaeospondylus, genus of enigmatic fossil vertebrates that were very fishlike in appearance but of uncertain relationships.......
paleoanthropology
paleoanthropology, interdisciplinary branch of anthropology concerned with the origins and development of early......
Paleocene Epoch
Paleocene Epoch, first major worldwide division of rocks and time of the Paleogene Period, spanning the interval......

Fossils & Geologic Time Encyclopedia Articles By Title