early fossils

trilobites
cynodonts
graptolites
stromatolites

Pre Cambrian Revisions (Stratigraphy)

Base Ediacaran System 635mya

The principal observed correlation events are (1) the rapid decay of Marinoan ice sheets and onset of distinct cap carbonates throughout the world, and (2) the beginning of a distinctive pattern of secular changes in carbon isotopes.

Pre-Cambrian eras and systems below Ediacaran are defined by absolute ages, rather than stratigraphic points.



Hadean Eon ~4600 informal term formation of planet earth
Archaean Eon
Eo ~4000 oldest preserved rocks on earth's surface
Paleo 3600
Meso 3200
Neo 2800
Proterozoic Eon
Paleoproterozoic Era
Siderian System 2500
Rhyacian System 2300
Orosirian System 2050
Stratherian System 1800
Mesoproterozoic Era
Calymmian System 1600
Ectasian System 1400
Stenian System 1200
Neoproterozoic Era
Tonian System 1000
Cryogenian System 850
base Ediacaran System 635

Geologic time and continents, climates, etc. (dict.com)

Proterozoic
Wikipedia, the free encyclopedia - Cite This Source

The Proterozoic is a geological eon representing a period before the first abundant complex life on Earth.

The Proterozoic Eon extended from 2500 Ma to 542.0 ± 1.0 Ma (million years ago). The Proterozoic is the most recent part of the old, informally named ‘Precambrian’ time.
The Proterozoic consists of 3 geologic eras, from oldest to youngest:

Paleoproterozoic
Mesoproterozoic
Neoproterozoic
The well-identified events were:

The transition to an oxygenated atmosphere during the Mesoproterozoic.
Several glaciations, including the hypothesized Snowball Earth during the Cryogenian period in the late Neoproterozoic. The Ediacaran Period (635 to 542 Ma) which is characterized by the evolution of abundant soft-bodied multicellular organisms.

The Proterozoic record
The geologic record of the Proterozoic is much better than that for the preceding Archean. In contrast to the deep-water deposits of the Archean, the Proterozoic features many strata that were laid down in extensive shallow epicontinental seas; furthermore, many of these rocks are less metamorphosed than Archean-age ones, and plenty are unaltered. Study of these rocks show that the eon featured massive, rapid continental accretion (unique to the Proterozoic), supercontinent cycles, and wholly-modern orogenic activity. The first known glaciations occurred during the Proterozoic, one began shortly after the beginning of the eon, while there were at least four during the Neoproterozoic, climaxing with the Snowball Earth of the Varangian glaciation.

The build-up of oxygen
One of the most important events of the Proterozoic was the gathering up of oxygen in the Earth's atmosphere. Though oxygen was undoubtedly released by photosynthesis well back in Archean times, it could not build up to any significant degree until chemical sinks — unoxidized sulfur and iron — had been filled; until roughly 2.3 billion years ago, oxygen was probably only 1% to 2% of its current level. Banded
iron formations, which provide most of the world's iron ore, were also a prominent chemical sink; most accumulation ceased after 1.9 billion years ago, either due to an increase in oxygen or a more thorough mixing of the oceanic water column.
Red beds, which are colored by hematite, indicate an increase in atmospheric oxygen after 2 billion years ago; they are not found in older rocks. The oxygen build-up was probably due to two factors: a filling of the chemical sinks, and an increase in carbon burial, which sequestered organic compounds that would have otherwise been oxidized by the atmosphere.

Paleogeography
Proterozoic life
The first advanced single-celled and multi-cellular life roughly coincides with the oxygen accumulation; this may have been due to an increase in the oxidized nitrates that eukaryotes use, as opposed to cyanobacteria. It was also during the Proterozoic that the first symbiotic relationships between mitochondria (for nearly all eukaryotes) and chloroplasts (for plants and some protists only) and their hosts evolved. The blossoming of eukaryotes such as acritarchs did not preclude the expansion of cyanobacteria; in fact, stromatolites reached their greatest abundance and diversity during the Proterozoic, peaking roughly 1.2 billion years ago.

Classically, the boundary between the Proterozoic and the Phanerozoic eons was set at the base of the Cambrian period when the first fossils of animals known as trilobites and archeocyathids appeared. In the second half of the 20th century, a number of fossil forms have been found in Proterozoic rocks, but the upper boundary of the Proterozoic has remained fixed at the base of the Cambrian, which is currently placed at 542 Ma.

The Paleoproterozoic (also spelled Palaeoproterozoic) is the first of the three sub-divisions (eras) of the Proterozoic occurring between 2500 Ma and 1600 Ma (million years ago). This is when the continents first stabilized. This is also when Cyanobacteria evolved, a type of bacteria which uses the biochemical process of photosynthesis to produce energy and oxygen. Before the significant increase in atmospheric oxygen almost all life that existed was anaerobic, that is, the metabolism of life depended on a form of cellular respiration that did not require oxygen. Free oxygen in large amounts is poisonous to most anaerobic bacteria, and at this time most life on Earth vanished. The only life that remained was either resistant to the oxidizing and poisonous effects of oxygen, or spent its life-cycle in an oxygen-free environment. This main event is called the Oxygen Catastrophe. Also the first Grypania fossils and the first Eukaryotes appeared during this time.

Mesoproterozoic
Wikipedia, the free encyclopedia - Cite This Source

The Mesoproterozoic Era is a geologic era that occurred between 1600 Ma and 1000 Ma (million years ago). The major events of this era are the formation of the Rodinia supercontinent, the breakup of the Columbia supercontinent, and the evolution of sexual reproduction

Paleogeology
Geologically, the Neoproterozoic is thought to comprise a time of complex continental motion as a supercontinent called Rodinia broke up into perhaps as many as eight pieces. Possibly as a consequence of continental rifting, several massive worldwide glaciations occurred during the Era including the Sturtian and Marinoan glaciations, the most severe the Earth has ever known. These are believed to have been so severe as to bring icecaps to the equator, leading to a state known as the "Snowball Earth".
Paleobiology
The idea of the Neoproterozoic Era came on the scene relatively recently — after about 1960. Nineteenth century paleontologists set the start of multicelled life at the first appearance of hard-shelled animals called trilobites and archeocyathids. This set the beginning of the Cambrian period. In the early 20th century, paleontologists started finding fossils of multicellular animals that predated the Cambrian boundary. A complex fauna was found in South West Africa in the 1920s but was misdated. Another was found in South Australia in the 1940s but was not thoroughly examined until the late 1950s. Other possible early fossils were found in Russia, England, Canada, and elsewhere (see Ediacaran biota). Some were determined to be pseudofossils, but others were revealed to be members of rather complex biotas
that are still poorly understood. At least 25 regions worldwide yielded metazoan fossils prior to the classical Cambrian boundary.

A few of the early animals appear possibly to be ancestors of modern animals. Most fall into ambiguous groups of frond-like animals(?); discoids that might be holdfasts for stalked animals(?) ("medusoids"); mattress-like forms; small calcaerous tubes; and armored animals of unknown provenance. These were most commonly known as Vendian biota until the formal naming of the Period, and are currently known as Ediacaran biota. Most were soft bodied. The relationships, if any, to modern forms are obscure. Some paleontologists relate many or most of these forms to modern animals. Others acknowledge a few possible or even likely relationships but feel that most of the Ediacaran forms are representatives of (an)
unknown animal type(s).

Terminal period
The nomenclature for the terminal period of the Neoproterozoic has been unstable. Russian geologists referred to the last period of the Neoproterozoic as the Vendian, and the Chinese called it the Sinian, and most Australians and North Americans used the name Ediacaran. However, in 2004, the International Union of Geological Sciences ratified the Ediacaran age to be a geological age of the Neoproterozoic, ranging from 630 +5/-30 to 542 +/- 0.3 million years ago. The Ediacaran boundaries are the only Precambrian boundaries defined by biologic Global Boundary Stratotype Section and Points, rather than the absolute Global Standard Stratigraphic Ages.



Cambrian paleogeography
Cambrian continents are thought to have resulted from the breakup of a Neoproterozoic supercontinent called Pannotia. The waters of the Cambrian period appear to have been widespread and shallow. Gondwana remained the largest supercontinent after the breakup of Pannotia. It is thought that Cambrian climates were significantly warmer than those of preceding times that experienced extensive
ice ages discussed as the Varanger glaciation. Also there was no glaciation at the poles. Continental drift rates in the Cambrian may have been anomalously high. Laurentia, Baltica and Siberia remained independent continents since the break-up of the supercontinent of Pannotia. Gondwana started to drift towards the South Pole. Panthalassa covered most of the southern hemisphere, and minor oceans
included the Proto-Tethys Ocean, Iapetus Ocean, and Khanty Ocean, all of which expanded by this time.

Ordovician paleogeography
Sea levels were high during the Ordovician; in fact during the Tremadocian, marine transgressions worldwide were the greatest for which evidence is preserved in the rocks. During the Ordovician, the southern continents were collected into a single continent called Gondwana. Gondwana started the period in equatorial latitudes and, as the period progressed, drifted toward the South Pole. Early in the Ordovician, the continents Laurentia, Siberia, and Baltica were still independent continents (since the break-up of the supercontinent Pannotia earlier), but Baltica began to move towards Laurentia later in the period, causing the Iapetus Ocean to shrink between them. Also, Avalonia broke free from Gondwana and began to head north towards Laurentia. Rheic Ocean was formed as a result of this.

Ordovician rocks are chiefly sedimentary. Because of the restricted area and low elevation of solid land, which set limits to erosion, marine sediments that make up a large part of the Ordovician system consist chiefly of limestone. Shale and sandstone are less conspicuous. A major mountain-building episode was the Taconic orogeny that was well under way in Cambrian times. By the end of the period, Gondwana had neared or approached the pole and was largely glaciated.

The Ordovician was a time of calcite sea geochemistry in which low-magnesium calcite was the primary inorganic marine precipitate of calcium carbonate. Carbonate hardgrounds were thus very common, along with calcitic ooids, calcitic cements, and invertebrate faunas with dominantly calcitic skeletons
(Stanley and Hardie, 1998, 1999).

Silurian paleogeography
During the Silurian, Gondwana continued a slow southward drift to high southern latitudes, but there is evidence that the Silurian icecaps were less extensive than those of the late Ordovician glaciation. The melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian
sediments overlie eroded Ordovician sediments, forming an unconformity. Other cratons and continent fragments drifted together near the equator, starting the formation of a second supercontinent known as Euramerica. When the proto-Europe collided with North America, the collision folded coastal sediments that had
been accumulating since the Cambrian off the east coast of North America and the west coast of Europe. This event is the Caledonian orogeny, a spate of mountain building that stretched from New York State through conjoined Europe and Greenland to Norway. At the end of the Silurian, sea levels dropped again, leaving telltale basins of evaporites in a basin extending from Michigan to West Virginia, and the new mountain ranges were rapidly eroded. The Teays River, flowing into the shallow
mid-continental sea, eroded Ordovician strata, leaving traces in the Silurian strata of northern Ohio and Indiana. The vast ocean of Panthalassa covered most of the northern hemisphere. Other minor oceans include, Proto-Tethys, Paleo-Tethys, Rheic Ocean, a seaway of Iapetus Ocean (now in between Avalonia and aurentia), and newly formed Ural Ocean.

Climate
During this period, the Earth entered a long warm greenhouse phase, and warm shallow seas covered much of the equatorial land masses. Early in the Silurian, glaciers retreated back into the South Pole until they almost disappeared in the middle of Silurian. The period witnessed a relative stabilization of the Earth's general climate, ending the previous pattern of erratic climatic fluctuations. Layers of broken shells (called coquina) provide strong evidence of a climate dominated by violent storms generated then as now by warm sea surfaces. Later in the Silurian, the climate cooled slightly, but in the Silurian-Devonian boundary, the climate became warmer.

Devonian palaeogeography
The Devonian period was a time of great tectonic activity, as Laurasia and Gondwanaland drew closer together. The continent Euramerica (or Laurussia) was created in the early Devonian by the collision of Laurentia and Baltica, which rotated into the natural dry zone along the Tropic of Capricorn, which is formed as
much in Paleozoic times as nowadays by the convergence of two great airmasses, the Hadley cell and the Ferrel cell. In these near-deserts, the Old Red Sandstone sedimentary beds formed, made red by the oxidized iron (hematite) characteristic of drought conditions.

Near the equator, Pangaea began to consolidate from the plates containing North America and Europe, further raising the northern Appalachian Mountains and forming the Caledonian Mountains in Great Britain and Scandinavia. The west coast of Devonian North America, by contrast, was a passive margin with deep silty embayments, river deltas and estuaries, in today's Idaho and Nevada; an approaching volcanic island arc reached the steep slope of the continental shelf in Late Devonian times and began to uplift deep water deposits, a collision that was the prelude to the mountain-building episode of Mississippian times called the Antler orogeny

The southern continents remained tied together in the supercontinent of Gondwana. The remainder of modern Eurasia lay in the Northern Hemisphere. Sea levels were high worldwide, and much of the land lay submerged under shallow seas, where tropical reef organisms lived. The deep, enormous Panthalassa (the "universal ocean") covered the rest of the planet. Other minor oceans were Paleo-Tethys, Proto-Tethys, Rheic Ocean, and Ural Ocean (which was closed during the collision with Siberia and Baltica). Devonian rocks are oil and gas producers in some areas.

Paleogeography
A global drop in sea level at the end of the Devonian reversed early in the Carboniferous; this created the widespread epicontinental seas and carbonate deposition of the Mississippian. There was also a drop in south polar temperatures; southern Gondwanaland was glaciated throughout the period, though it is uncertain if the ice sheets were a holdover from the Devonian or not. These conditions apparently had little effect in the deep tropics, where lush coal swamps flourished within 30 degrees of the northernmost glaciers.

A mid-Carboniferous drop in sea-level precipitated a major marine extinction, one that hit crinoids and ammonites especially hard. This sea-level drop and the associated unconformity in North America separate the Mississippian period from the Pennsylvanian period.

The Carboniferous was a time of active mountain-building, as the supercontinent Pangaea came together. The southern continents remained tied together in the supercontinent Gondwana, which collided with North America-Europe (Laurussia) along the present line of eastern North America. This continental collision resulted in the Hercynian orogeny in Europe, and the Alleghenian orogeny in North America; it
also extended the newly-uplifted Appalachians southwestward as the Ouachita Mountains. In the same time frame, much of present eastern Eurasian plate welded itself to Europe along the line of the Ural mountains. Most of the Mesozoic supercontinent of Pangea was now assembled, although North China (which would collide in the Latest Carboniferous), and South China continents were still separated from Laurasia. The Late Carboniferous Pangaea was shaped like an "O".
There were two major oceans in the Carboniferous—Panthalassa and Paleo-Tethys, which was inside the "O" in the Carboniferous Pangaea. Other minor oceans were shrinking and eventually closed - Rheic Ocean (closed by the assembly of South and North America), the small, shallow Ural Ocean (which was closed by the collision of Baltica and Siberia continents, creating the Ural Mountains) and Proto-Tethys
Ocean (closed by North China collision with Siberia/Kazakhstania.

Climate
The early part of the Carboniferous was mostly warm; in the later part of the Carboniferous, the climate cooled. Glaciations in Gondwana, triggered by Gondwana's southward movement, continued into the Permian and because of the lack of clear markers and breaks, the deposits of this glacial period are often referred to as Permo-Carboniferous in age.

Historical Geology of the Period
The Lower Permian
During the Permian period, changes in the earth's surface that had begun in the preceding Carboniferous period reached a climax. At the close of the Carboniferous, large areas of E North America were dry land. In the Lower Permian, sandy shales, sandstones, and thin limestones of the Dunkard formation (formerly called the Upper Barren measures) were deposited in the remaining submerged areas of West Virginia, Pennsylvania, and Ohio, but the continued rising of the land soon put an end to deposition. The Dunkard is the last Paleozoic formation of the E United States. More extensive deposits were formed in the West. Parts of Texas, Oklahoma, Kansas, and Nebraska were covered by an arm of the sea or possibly by one or more salt lakes or lagoons, now represented by masses of salt or gypsum in layers separated and overlaid by red beds. There are important Permian salt mines at Hutchinson and Lyons in Kansas and gypsum mines in Oklahoma, Texas, and Kansas. The longest marine submergence of the Lower Permian in North America was in W Texas and SE New Mexico, where there is a system of marine limestones and sandstones 4,000 to 6,000 ft (1,200-1,800 m) thick. The Cordilleran region was also submerged; here marine beds are more common toward the west, and land sediments, especially red beds, toward the east. The red beds are generally considered to be indicative of increasingly arid conditions in Permian times. n Europe, the Lower Permian, or Rotliegendes [red layers], was marked principally by erosion from the Paleozoic Alps of the Carboniferous into the low-lying land to the north; the formations are chiefly shale
and sandstone, with some conglomerate and breccia. Red is a prominent color for the beds. The Pangaea supercontinent formed from an aggregation of all continents at this time.The Permian and late Carboniferous of the Southern Hemisphere were radically different from those of the Northern Hemisphere. Australia, S Africa, and South America experienced a series of glacial periods, as is shown by the presence of tillite and of conspicuous striations of the underlying rock formations. This
condition prevailed also in India. Paleozoic glaciation in North America is suggested by the Squantum tillite near Boston, Mass. This glaciation and the aridity of which the red beds seem to be the result are the two most strongly marked characteristics of the Permian period.

The Upper Permian
In the Upper Permian practically all of North America was above sea level, and the continent was larger than at present. Toward the close of the Upper Permian the greatest earth disturbance of the Paleozoic era thrust up the Appalachian Mts. In Europe, the Upper Permian was a period of more extensive marine invasion; the Zechstein formation is predominantly limestone, though it includes rich deposits of copper, salt, gypsum, and potash. The Upper Permian beds of Germany were long the chief source of the world's potash.

Paleogeography
During the Permian, all the Earth's major land masses except portions of East Asia were collected into a single supercontinent known as Pangaea. Pangaea straddled the equator and extended toward the poles, with a corresponding effect on ocean currents in the single great ocean ("Panthalassa", the "universal sea"), and the Paleo-Tethys Ocean, a large ocean that was between Asia and Gondwana. The Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, causing the Paleo-Tethys to shrink. A new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic Era. Large continental landmasses create climates with extreme variations of heat and cold ("continental climate") and monsoon conditions with highly seasonal rainfall patterns. Deserts seem to have been widespread on Pangaea. Such dry conditions favored gymnosperms, plants with seeds
enclosed in a protective cover, over plants such as ferns that disperse spores. The first modern trees (conifers, ginkgos and cycads) appeared in the Permian.

Three general areas are especially noted for their Permian deposits- the Ural Mountains (where Perm itself is located), China, and the southwest of North America, where the Permian Basin in the U.S. state of Texas is so named because it has one of the thickest deposits of Permian rocks in the world.

Climate
As the Permian opened, the Earth was still in the grip of an ice age, so the polar regions were covered with deep layers of ice. Glaciers continued to cover much of Gondwanaland, as they had during the late Carboniferous . At the same time the tropics were covered in swampy forests. Towards the middle of the period the climate became warmer and milder, the glaciers receded, and the continental interiors became drier. Much of the interior of Pangaea was probably arid, with great seasonal
fluctuations (wet and dry seasons), because of the lack of the moderating effect of nearby bodies of water. This drying tendency continued through to the late Permian, along with alternating warming and cooling periods.

Paleogeography
During the Triassic, almost all the Earth's land mass was concentrated into a single supercontinent centered more or less on the equator, called Pangaea ("all the land"). This took the form of a giant "Pac-Man" with an east-facing "mouth" constituting the Tethys sea, a vast gulf that opened farther westward in the mid-Triassic, at the expense of the shrinking Paleo-Tethys Ocean, an ocean that existed
during the Paleozoic. The remainder was the world-ocean known as Panthalassa ("all the sea"). All the deep-ocean sediments laid down during the Triassic have disappeared through subduction of oceanic plates; thus, very little is known of the Triassic open ocean. The supercontinent Pangaea was rifting during the Triassic—especially late in the period—but had not yet separated. The first nonmarine sediments in the rift that marks the initial break-up of Pangea—which separated New Jersey from Morocco—are of Late Triassic age; in the U.S., these thick sediments
comprise the Newark Group. Because of the limited shoreline of one super-continental mass, Triassic marine deposits are globally relatively rare, despite their prominence in Western Europe, where the Triassic was first studied. In North America, for example, marine deposits are limited to a few exposures in the west. Thus Triassic stratigraphy is mostly based on organisms living in lagoons and hypersaline environments, such as Estheria crustaceans.

Climate
The Triassic climate was generally hot and dry, forming typical red bed sandstones and evaporites. There is no evidence of glaciation at or near either pole; in fact, the polar regions were apparently moist and temperate, a climate suitable for reptile-like creatures. Pangaea's large size limited the moderating effect of the global ocean; its continental climate was highly seasonal, with very hot summers and cold winters. It probably had strong, cross-equatorial monsoons.

Paleogeography
During the early Jurassic, the supercontinent Pangaea broke up into the northern supercontinent Laurasia and the southern supercontinent Gondwana; the Gulf of Mexico opened in the new rift between North America and what is now Mexico's Yucatan Peninsula. The Jurassic North Atlantic Ocean was relatively narrow, while the South Atlantic did not open until the following Cretaceous Period, when Gondwana itself
rifted apart. The Tethys Sea closed, and the Neotethys basin appeared. Climates were warm, with no evidence of glaciation. As in the Triassic, there was apparently no land near either pole, and no extensive ice caps existed.

The Jurassic geological record is good in western Europe, where extensive marine sequences indicate a time when much of the continent was submerged under shallow tropical seas; famous locales include the Jurassic Coast World Heritage Site and the renowned late Jurassic lagerstätten of Holzmaden and Solnhofen. In contrast, the North American Jurassic record is the poorest of the Mesozoic, with few outcrops at the surface. Though the epicontinental Sundance Sea left marine deposits in parts of the northern plains of the United States and Canada during the late Jurassic, most exposed sediments from this period are continental, such as the alluvial deposits of the Morrison Formation. The Jurassic was a time of calcite sea geochemistry in which low-magnesium calcite was the primary inorganic marine precipitate of calcium carbonate. Carbonate hardgrounds were thus very common, along with calcitic ooids, calcitic cements, and invertebrate faunas with dominantly calcitic skeletons (Stanley and Hardie, 1998, 1999).

The first of several massive batholiths were emplaced in the northern Cordillera beginning in the mid-Jurassic, marking the Nevadan orogeny. Important Jurassic exposures are also found in Russia, India, South America, Japan, Australasia, and the United Kingdom.

Historical Geology of the Period
The Lower Cretaceous Period
At the beginning of the Lower Cretaceous in North America, the Mexican Sea of the late Jurassic period spread over Texas, Oklahoma, New Mexico, and parts of Arizona, Kansas, and Colorado. Deposits from this inland sea, known as the Comanchean Sea, were chiefly limestone (up to 1,500 ft/457 m thick in Texas) but some continental sediments (i.e., sandstone, shale, and conglomerate) mark the reemergence of land, which brought the Lower Cretaceous to a close. The Comanchean Sea was probably separated by a land barrier from contemporaneous seas in the California areas, where 26,000 ft (7,925 m) of Shastan shales, with sandstone and thin limestone, were laid down. The sediments were derived by rapid erosion from the recently elevated Sierra Nevada and Klamath mts. In Montana,Alberta, and British Columbia the Kootenai deposits of sandstone and sandy shale, which contain workable deposits of good coal, were formed; along the Atlantic coast the unconsolidated sandy clay, gravel, and sand of the Potomac series were deposited.

The Lower Cretaceous opened in NW Europe with the deposition of a continental and freshwater formation, the Wealden sand and clay, best displayed in England. The sea, meanwhile, expanded from the Mediterranean, finally overlaying successive Wealden strata with limestone. There was at the same time an extensive sea in N Europe. At the close of the Lower Cretaceous, there was some recession of the seas; by the Upper Cretaceous, the great transgression of seas submerged lands that had been open since the Paleozoic.

The Upper Cretaceous Period
The Upper Cretaceous opened in W North America with the deposition of continental sands (now the Dakota sandstone), which, however, were covered by the ensuing rise of the Colorado Sea. The Colorado Sea was the greatest of the North American Mesozoic seas and extended all the way from Mexico up into the Arctic, covering most of central North America. The Colorado deposits were composed chiefly of shales, limestone, and some chalk in Kansas and South Dakota. Slight shifting of the sea was followed by the deposition of the Montana shale and sandstone and then by withdrawal of the sea. Near the end of the Upper Cretaceous, conditions in the west were similar to those of the Carboniferous period in other regions; swamps and bogs were formed that later became valuable deposits of coal.

At the close of the Cretaceous the Laramide revolution occurred—at least two different epochs of mountain building and one of relative quiet. In this disturbance the Rockies and the E Andes were first elevated, and there were extensive flows of lava. The Appalachians, which had been reduced almost to base level by erosion, were rejuvenated, and the seas retreated from all parts of the continent. The intermittent character of the Laramide disturbance makes difficult the demarcation of the Mesozoic and the succeeding Cenozoic era.

The striking feature of the European Upper Cretaceous are great chalk deposits from small carbonate-bearing marine algae and calcareous fauna, now exposed in the cliffs of the English Channel. In India the late Upper Cretaceous was marked by an overflow of lava in the Deccan plateau. The area covered by igneous rocks dating from this period now comprises over 200,000 sq mi (518,000 sq km) and was formerly much larger, having been reduced by erosion. Near Mumbai the formation is 10,000 ft (3,000 m) thick.

Movement of the Continents
During the Cretaceous period the massive continents of Gondwanaland and Laurasia continued to separate. South America and Africa had separated, with the consequent widening of the S Atlantic. The N Atlantic continued to expand, although it appears that Europe, Greenland, and North America were still connected. Madagascar had separated from Africa, while India was still drifting northward toward Asia. The Tethys Sea was disappearing as Africa moved north toward Eurasia. Antarctica and Australia had yet to separate.

Paleogeography
During the Cretaceous, the late Paleozoic - early Mesozoic supercontinent of Pangaea completed its breakup into present day continents, although their positions were substantially different at the time. As the Atlantic Ocean widened, the convergent-margin orogenies that had begun during the Jurassic continued in the North American Cordillera, as the Nevadan orogeny was followed by the Sevier and Laramide orogenies.
Though Gondwana was still intact in the beginning of the Cretaceous, it broke up as South America, Antarctica and Australia rifted away from Africa (though India and Madagascar remained attached to each other); thus, the South Atlantic and Indian Oceans were newly formed. Such active rifting lifted great undersea mountain chains along the welts, raising eustatic sea levels worldwide. To the north of Africa the Tethys Sea continued to narrow. Broad shallow seas advanced across central North America (the Western Interior Seaway) and Europe, then receded late in the period, leaving thick marine deposits sandwiched between coal beds. At the peak of the Cretaceous transgression, one-third of Earth's present land area was submerged.

The Cretaceous is justly famous for its chalk; indeed, more chalk formed in the Cretaceous than in any other period in the Phanerozoic. Mid-ocean ridge activity--or rather, the circulation of seawater through the enlarged ridges--enriched the oceans in calcium; this made the oceans more saturated, as well as increased the bioavailability of the element for calcareous nanoplankton. These widespread carbonates and other sedimentary deposits make the Cretaceous rock record especially fine. Famous formations from North America include the rich marine fossils of Kansas's Smoky Hill Chalk Member and the terrestrial fauna of the late Cretaceous Hell Creek Formation. Other important Cretaceous exposures occur in Europe and China. In the area that is now India, massive lava beds called the Deccan Traps
were erupted in the very late Cretaceous and early Paleocene.

Climate
The Berrasian epoch showed a cooling trend that had been seen in the last epoch of the Jurassic. There is evidence that snowfalls were common in the higher latitudes and the tropics became wetter than during the Triassic and Jurassic. Glaciation was however restricted to alpine glaciers on some high-latitude mountains, though seasonal snow may have existed further south. After the end of the Berrasian, however, temperatures increased again, and these conditions were almost constant until the end of the period. This trend was due to intense volcanic activity which
produced large quantities of carbon dioxide. The development of a number of mantle plumes across the widening mid-ocean ridges further pushed sea levels up, so that large areas of the continental crust were covered with shallow seas. The Tethys Sea connected the tropical oceans east to west also helped warm the global climate. Warm-adapted plant fossils are known from localities as far north as Alaska and Greenland, while dinosaur fossils have been found within 15 degrees of the Cretaceous south pole. A very gentle temperature gradient from the equator to the poles meant weaker global winds, contributing to less upwelling and more stagnant oceans than today. This evidenced by widespread black shale deposition and frequent anoxic events. Sediment cores show that tropical sea surface temperatures may have briefly been as warm as 42 °C (107 °F), 17 °C (31 °F) warmer than at present, and that they averaged around 37 °C. Meanwhile deep ocean temperatures were as much as
15 to 20 °C (27 to 36 °F) higher than today's.,

The Paleogene (alternatively Palaeogene) period is a unit of geologic time that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic era. Lasting 42 million years, the Paleogene is most notable as being the time in which mammals evolved from relatively small, simple forms into a plethora of diverse animals in the wake of the mass extinction that ended the
preceding Cretaceous Period. Some of these mammals would evolve into large forms that would dominate the land, while others would become capable of living in marine, specialized terrestrial and even airborne environments. Birds also evolved considerably during this period changing into roughly-modern forms. Most other branches of life on earth remained relatively unchanged in comparison to birds and
mammals during this period. Some continental motion took place. Climates cooled somewhat over the duration of the Paleogene and inland seas retreated from North America early in the Period. This period consists of the Paleocene, Eocene, and Oligocene Epochs. The end of the Paleocene (55.5/54.8 Ma) was marked by one of the most significant periods of global change during the Cenozoic, a sudden global change, the Paleocene-Eocene Thermal Maximum, which upset oceanic and atmospheric
circulation and led to the extinction of numerous deep-sea benthic foraminifera and on land, a major turnover in mammals.The Paleogene follows the Cretaceous Period and is followed by the Miocene Epoch of the Neogene Period. The terms 'Paleogene System' (formal) and 'lower Tertiary System' (informal) are applied to the rocks deposited during the 'Paleogene Period'. The somewhat confusing terminology seems to be due to attempts to deal with the comparatively fine subdivisions of time possible in the
relatively recent geologic past, when more information is preserved. By dividing the Tertiary Period into two periods instead of five epochs, the periods are more closely comparable to the duration of 'periods' in the Mesozoic and Paleozoic Eras.



Notes

Neogene Period is a unit of geologic time starting 23.03 ± 0.05 million years ago. The Neogene Period follows the Paleogene Period of the Cenozoic Era. Under the current proposal of the International Commission on Stratigraphy (ICS), the Neogene would consist of the Miocene, Pliocene, Pleistocene, and Holocene epochs and continue until the present.

The terms Neogene System (formal) and upper Tertiary System (informal) describe the rocks deposited during the Neogene Period. The Neogene covers roughly 23 million years. During the Neogene mammals and birds evolved considerably. Most other forms were relatively unchanged. Some continental motion took place, the most significant event being the connection of North and South America in the late Pliocene. Climates cooled somewhat over the duration of the Neogene culminating in continental glaciations in the Quaternary sub-era (or period, in some time scales) that follows, and that saw the dawn of the genus Homo.


Controversy
The Neogene traditionally ended at the end of the Pliocene epoch, just before the older definition of the beginning of the Quaternary Period; many time scales show this division. However, there is a movement amongst geologists (particularly Neogene Marine Geologists) to also include ongoing geological time (Quaternary) in the Neogene, while others (particularly Quaternary Terrestrial Geologists) insist the
Quaternary to be a separate period of distinctly different record. The somewhat confusing terminology and disagreement amongst geologists on where to draw what hierarchical boundaries, is due to the comparatively fine divisibility of time units as time approaches the present, and due to geological preservation that causes the youngest sedimentary geological record to be preserved over a much larger area and reflecting many more environments, than the slightly older geological record. By dividing the Cenozoic era into three (arguably two) periods (Paleogene, Neogene, Quaternary) instead of 7 epochs, the periods are more closely comparable to the duration of periods in the Mesozoic and Paleozoic eras. The ICS once proposed that the Quaternary be considered a sub-era (sub-erathem) of the Neogene, with a beginning date of 2.588 Ma., namely the start of the Gelasian Stage. The International Union for Quaternary Research (INQUA) counterproposed that the Neogene and the Pliocene end at 2.588 Ma., that the Gelasian be transferred to the Pleistocene, and the Quaternary be recognized as the third period in the Cenozoic, citing the key changes in Earth's climate, oceans, and biota that occurred 2.588 Ma. and its correspondence to the Gauss-Matuyama magnetostratigraphic boundary. 2006 ICS and INQUA reached a compromise that made Quaternary a subera, subdividing Cenozoic into the old classical Tertiary and Quaternary, a compromise that was rejected by International Union of Geological Sciences because it split both Neogene and Pliocene in two.

Notes on timescales & biota (dictionary.com)

Cambrian fauna
Of those modern animal phyla that fossilize easily, all save the bryozoans appear to have representatives in the Cambrian, and of these most (except the considerably older sponges) seem to have originated near the start of the period. Many extinct phyla and odd animals that have unclear relationships to other animals also appear in the Cambrian. The apparent "sudden" appearance of very diverse faunas over a period of no more than a few tens of millions of years is referred to as the "Cambrian Explosion". Also, the first possible tracks on land, such as Protichnites and Climactichnites, dating to about 530 mya and found in Ontario, Canada, and northern United States, appeared at this time. The conodonts, small predatory primitive chordates known from their fossilised teeth, also appeared during the Furongian epoch of the Cambrian period. The conodonts thrived throughout the Paleozoic and the early Mesozoic until they completely disappeared during the Late Triassic period when the first mammals were evolving.
The best studied sites where the soft parts of organisms have fossilized are in the Burgess shale of British Columbia. They represent strata from the Middle Cambrian and provide us with a wealth of information on early animal diversity. Similar faunas have subsequently been found in a number of other places — most importantly in very early Cambrian shales in the People's Republic of China's Yunnan Province (see Maotianshan shales). Fairly extensive Precambrian Ediacaran faunas have been identified in the past 50 years, but their relationships to Cambrian forms are quite obscure.
Cambrian flora
Generally it is accepted that there were no land plants at this time although molecular dating suggests that land plant ancestors diverged from the algae much earlier, in the Neoproterozoic about 700 ma, and that fungi diverged from the animals about 1 billion years ago. The land at this time was barren, mostly desert and badlands.

The Ordovician seas were rich in animal life. The most characteristic invertebrates were minute graptolites, other numerous forms being brachiopods, bryozoans, and trilobites. Some cystoids and crinoids appeared; there were a few corals and many cephalopods. Especially noteworthy was the appearance of a few primitive, fishlike vertebrates (jawless fishes) and tiny land plants resembling liverworts.
Ordovician fauna
Though less famous than the Cambrian explosion, the Ordovician featured an adaptive radiation that was no less remarkable; marine faunal genera increased fourfold, resulting in 12% of all known Phanerozoic marine fauna. The trilobite, inarticulate brachiopod, archaeocyathid, and eocrinoid faunas of the Cambrian were succeeded by those which would dominate for the rest of the Paleozoic, such as articulate brachiopods, cephalopods, and crinoids; articulate brachiopods, in particular, largely replaced trilobites in shelf communities. Their success epitomizes the greatly increased diversity of carbonate shell-secreting organisms in the Ordovician compared to the Cambrian.In North America and Europe, the Ordovician was a time of shallow continental seas rich in life. Trilobites and brachiopods in particular were rich and diverse. The first bryozoa appeared in the Ordovician as did the first coral reefs. Solitary corals date back to at least the Cambrian. Molluscs, which had also appeared during the Cambrian or the Ediacaran, became common and varied, especially bivalves, gastropods, and nautiloid cephalopods. It was long thought that the first true vertebrates (fish - Ostracoderms) appeared
in the Ordovician, but recent discoveries in China reveal that they probably originated in the Early Cambrian. The very first jawed fish appeared in the Late Ordovician epoch. Now-extinct marine animals called graptolites thrived in the oceans. Some cystoids and crinoids appeared.
During the Middle Ordovician there was a large increase in the intensity and diversity of bioeroding organisms. This is known as the Ordovician Bioerosion Revolution (Wilson & Palmer, 2006). It is marked by a sudden abundance of hard substrate trace fossils such as Trypanites, Palaeosabella and Petroxestes.
Trilobites in the Ordovician were very different than their predecessors in the Cambrian, Many trilobites developed bizarre spines and nodules to defend against predators such as primitive sharks and Nautiloid cephalopods while other trilobites such as Aeglina prisca evolved to become swimming forms. Some trilobites even developed shovel-like snouts for ploughing through muddy sea bottoms. Another unusual clade of trilobites known as the Trinucleids developed a broad pitted margin around their head shields. Other trilobites such as (Asaphus kowalewski) evolved long eyestalks to assist in detecting predators while some trilobite eyes by contrast took the opposing evolutionary direction and disappeared completely.
Ordovician florareen algae were common in the Ordovician and Late Cambrian (perhaps earlier). Plants probably evolved from green algae. The first terrestrial plants appeared in the form of tiny non-vascular plants resembling liverworts. Fossil spores from land plants have been identified in uppermost Ordovician sediments, but among the first land fungi may have been Arbuscular mycorrhiza fungi (Glomerales), playing a crucial role in facilitating the colonization of land by plants through mycorrhizal symbiosis, which makes mineral nutrients available to plant cells; such fossilized fungal hyphae and spores from the Ordovician of Wisconsin have been found with an age of about 460 mya, a time when the land flora most likely only consisted of plants similar to non-vascular bryophytes. Marine fungi were abundant in the Ordovician seas to decompose animal carcasses, and other wastes.


Dominating the life of the Silurian were marine invertebrates, including crinoids and cystoids, mollusks, and eurypterids, invertebrates related to crabs and insects. Members of the trilobite family were still numerous; primitive fishes increased in number. Also notable in the Silurian fauna were scorpions, possibly the first animals to live on land and take their oxygen from the air.
First terrestrial biota
The Silurian was the first period to see extensive terrestrial biota, in the form of moss forests along lakes and streams. Dominating these early colonisation of land was liverworts and hornworts. Mosses, not having roots would not have been able to hold on to the first soils. Some authorities have suggested erosion of the primitive soil is the reason for the often brownish appearance of Silurian sediments. Myriapods became the first proper terrestrial animals inhabiting the early moss and early vascular plant forets. The terrestrial ecosystems included the first multicellular terrestrial animals that have been identified, relatives of modern spiders and millipedes whose fossils were discovered in the 1990s.
The first fossil records of vascular plants, that is, land plants with tissues that carry food, appeared in the second half of the Silurian period. The earliest known representatives of this group are the Cooksonia (mostly from the northern hemisphere) and Baragwanathia (from Australia). A primitive Silurian land plant with xylem and phloem but no differentiation in root, stem or leaf, was much-branched Psilophyton, reproducing by spores and breathing through stomata on every surface, and probably photosynthesizing in every tissue exposed to light. Rhyniophyta and primitive lycopods were other land plants that first appear during this period.
The most notable Devonian animals were the jawed and bony fishes, which appeared in great numbers toward the close of the period. Conspicuous types were sharks, armored fishes, lungfishes, and ganoid fishes. Common invertebrates of the Devonian were crinoids, starfishes, sponges, and early ammonites; trilobites and graptolites became scarcer. An unusual surge of coral reef growth also occurred and corals were never again as prolific. Of land animals, the chief vestige is the footprint of a primitive salamanderlike amphibian in the Upper Devonian of Pennsylvania. Trees made their first appearance; the Devonian plants were the earliest to be extensively preserved as fossils, but their high degree of development suggests that more primitive forms existed earlier.
The Devonian is a geologic period of the Paleozoic era spanning from . It is named after Devon, England, where Exmoor rocks from this period were first studied.
During the Devonian Period, which occurred in the Paleozoic era, the first fish evolved legsand started to walk on land as tetrapods around 365 Ma, and the first insects and spiders also started to colonize terrestrial habitats. The first seed-bearing plants spread across dry land, forming huge forests. In the oceans, primitive sharks became more numerous than in the Silurian and the late Ordovician, and the first lobe-finned and bony fish. The first ammonite mollusks appeared, and trilobites, the mollusc-like brachiopods, as well as great coral reefs were still common. The Late Devonian extinction severely affected marine life.
The paleogeography was dominated by the supercontinent of Gondwana to the south, the continent of Siberia to the north, and the early formation of the small supercontinent of Euramerica in the middle.

The plant life of the Carboniferous period was extensive and luxuriant, especially during the
Pennsylvanian. It included ferns and fernlike trees; giant horsetails, called calamites; club mosses, or lycopods, such as Lepidodendron and Sigillaria; seed ferns; and cordaites, or primitive conifers. Land animals included primitive amphibians, reptiles (which first appeared in the Upper Carboniferous), spiders, millipedes, land snails, scorpions, enormous dragonflies, and more than 800 kinds of cockroaches. The inland waters were inhabited by fishes, clams, and various crustaceans; the oceans, by mollusks, crinoids, sea urchins, and one-celled foraminifera.
Evolution of Plant and Animal Life
Many marine animals became extinct during the Permian, but there was at the same time an evolution to more modern types, a marked change in the insects, and a notable increase in numbers and varieties of reptiles mainly because of the continental changes. Among plants, Lepidodendron and Sigillaria became rare, but ferns and conifers persisted. The widely distributed "seed fern," Glossopteris, which was apparently successful in resisting glacial conditions, was the most conspicuous development in the Permian flora. The presence of Glossopteris in South America, Antarctica, Australia, and S Africa is a strong argument favoring the interconnection of these land masses in a large supercontinent during Permian time. The end of the Permian is marked in the fossil record by a mass extinction.

Epoch and age refer to time, and equivalents series and stage refer to the rocks.

The climate of the Triassic was semiarid to arid. In the plant life, marine algae were abundant, ferns and tree ferns less important than in the Paleozoic, conifers dominant among the trees, and a new group, the cycads, appeared. Many Paleozoic invertebrates appeared for the last time in the Triassic. The ammonites became very important, then were reduced at the end of the Triassic to one species, but were destined to become numerous again in the succeeding Jurassic period. Amphibians were apparently not as numerous as in the Paleozoic, but some types were more highly developed. The dominant animals of the Triassic were the reptiles; although the Triassic reptiles were less specialized than those of the Jurassic, there were already a number of types of dinosaurs, pterosaurs, and marine reptiles. The Triassic rocks also contain the fossils of the earliest known mammals. The history of the European Jurassic is very well known, that system being one of the most complete on the Continent. Studies of oxygen isotopes, the extent of land flora, and marine fossils indicate that climates during Jurassic times were mild—perhaps 15°F; (8°C;) warmer than those of today. No glaciers existed during this period. The plant life of the Jurassic was dominated by the cycads, but conifers, ginkgoes, horsetails, and ferns were also abundant. Of the marine invertebrates, the most important were the ammonites. The dominant animals on land, in the sea, and in the air were the reptiles. Dinosaurs, more numerous and more extraordinary than those of the Triassic period, were the chief land animals; crocodiles, ichthyosaurs, and plesiosaurs ruled the sea, while the air was inhabited by the pterosaurs and relatives. Mammals, making their first appearance, were few and small but undoubtedly
became well established during the Jurassic period. The Jurassic saw the appearance of the first bird, Archaeopteryx.
The Lower Cretaceous is characterized by a revolution in the plant life, with the sudden appearance of flowering plants (angiosperms) such as the ancestors of the beech, fig, magnolia, and sassafras. By the end of the Cretaceous such plants became dominant. Willow, elm, grape, laurel, birch, oak, and maple also made their appearance, along with grass and the sequoias of California. Closely associated with the angiosperms were insects, including a form of the dragonfly, and most were similar to today's insects. This prepared the way for the increase in mammals in the late Cenozoic. The marine invertebrates of the Cretaceous included nautiluses, barnacles, lobsters, crabs, sea urchins, ammonites, and foraminifers. Reptiles reached their zenith, including the dinosaurs Triceratops, Tyrannosaurus, Stegosaurus, Apatosaurus (Brontosaurus), and Iguanodon, and ranged from herbivores to carnivores. Flying reptiles
such as the pterosaurs were highly developed, while in the sea there were ichthyosaurs, plesiosaurs, and mosasaurs. Other reptiles living in this period include crocodiles and giant turtles; snakes and lizards made their first appearance at this time. True mammals, which had already appeared in the Triassic period, were rare, as the Cretaceous reptiles dominated.
The climate of the Cretaceous was apparently fairly mild and uniform, but it is possible that toward the end of the period some variant zones of climate had appeared, making the overall climate cooler. Such changes, along with changes in both the earth's surface and its flora and fauna, brought the Mesozoic to a close. By the end of the Cretaceous, about 75% of all species, including marine, freshwater, and terrestrial organisms, became extinct. The rather abrupt disappearance of Cretaceous life remains a mystery. Theories for the extinctions include one or a mixture of the following: drastic cooling of the globe, retreat of the seas, breakup of the continents (see continental drift), biological disease, reversals of the earth's magnetic field, or a change in atmospheric carbon dioxide and oxygen. Another popular theory was introduced in 1980 by Luis Alvarez and colleagues at the Univ. of California. Alvarez proposed that the
earth was struck by an asteroid or comet about 6 mi (10 km) in diameter around 65 million years ago. Such an impact (or collection of impacts) would spread dust into the atmosphere, suppressing photosynthesis and changing the food chain. Evidence for an impact includes an anomalous iridium layer, typical of meteorites, and some probable impact craters dated to the late Cretaceous.

Various info

I. Tolweb
animalia-notocord-nerve cord-visceral (pharyngeal, gill) clefts or arches
Myxinidae (Myxine+Neomyxine)
fossilsCraniata
Amniota-synapsida=therapsida
hagfish (Myxinikela)330mya late C
lamprey (Mayomyzon, Hardistiella, Pipiscius) lateC of USA
anaspids? or lampreys
-Jamoytius (Early Silurian of Scotland)
-Euphanerops (Late Devonian of Canada)
Euconodonts (Middle Cambrian (540 million years) to the Late Triassic (230 million years);Carboniferous of Scotland; Ordovician of South Africa.)
Pteraspidomorphi, or pteraspidomorphs, is a group of fossil jawless vertebrates Early Ordovician to the Late Devonian (i.e. from 470 to 370 million years ago
he Anaspida, or anaspids, are a group of fossil, jawless vertebrates which lived in the Silurian (-430 to -410 million years ago)
The Galeaspida, or galeaspids, are a highly diversified group of fossil, armored, jawless vertebrates, which lived in Silurian and Devonian times (430 to 370 million years ago).
The Pituriaspida are a small group of fossil, armored jawless vertebrates, only known by two genera, Pituriaspis and Neeyambaspis, from the late Early Devonian or early Middle Devonian (about 390 million years) of Queensland, Australia
The Gnathostomata, or gnathostomes, are the majority of the Middle Devonian (-380 million years ago) to Recent vertebrates. Extant gnathostomes fall into two major clades, the Chondrichthyes and Osteichthyes. In addition, there are two extinct major gnathostome clades, the Placodermi (Early Silurian-Late Devonian) and the Acanthodii (Latest Ordovician or Earliest Silurian - Early Permian).
The oldest known skeletal remains of terrestrial vertebrates were found in the Upper Devonian of East Greenland (Clack, 1994). The presence of Lower to Middle Devonian trackways in Australia has led to suggestions that this group may have originated in the Lower Devonian, at least 400 million years ago (Tetrapods originated no later than the Mississippian (about 350 million years ago), the period from which the oldest known relatives of living amphibians are known.The oldest amniotes currently known date from the Middle Pennsylvanian locality known as Joggins, in Nova Scotia (Carroll, 1964). The relationships of these fossils indicate that amniotes first diverged into two lines, one line (Synapsida) that culminated in living mammals, and another line (Sauropsida) that embraces all the living reptiles (including birds). ... suggests that the more inclusive clade of which turtles (Testudines) are part (Anapsida) in most
morphological phylogenies had diverged as well, even though its current record extends back only to the Lower Permian (Laurin & Reisz, 1995). The earliest known salientian is †Triadobatrachus massinoti, from the Early Triassic of Madagascar. This "proto-frog" is about 250 million years old. "Proto-frog" refers to the fact that it had not yet quite evolved
the combination of features that are typically associated with frogs. For more information see
†Triadobatrachus massinoti. The earliest "true" frogs include †Prosalirus bitis and †Vieraella herbsti, from the Early Jurassic era. Thus, perfectly respectable frogs were around just before most of the major groups of dinosaurs had appeared. †Notobatrachus degiustoi from the Middle Jurassic is just a bit younger, about 155-170 million
years old.
********
II. UCMP
Actinopterygii-earliest Devonian-dominant by late paleozoic-paleoniscoids C to Triassic, extinct by end of Mesozoic (sturgeon, paddlefish relatives)-holosteans MZ (bowfish rel)-teleosts late Triassic dom by CZ
Sarcopterygii lobe-finned fish(lower Devonian) & tetrapodscentral appendage in fins, enamel on teeth, asymmetric tail originally
-Tetrapods
Anapsids mid-Pen AmphibiansElginerpeton 368mya ScotlandIchthyostega 363mya Greenland
Vertebrates: Fossil Record Because bone is resistant to decay, the fossil record of vertebrates is extensive and has been studied for over 200 years. We can't present all of it on one page; visit our exhibits on specific vertebrate groups for more detailed information. But to give a very brief summary:
The first known vertebrate fossils, found at the Chengjiang locality in China, date back to the early Cambrian. These early vertebrates, such as Haikouichthys, are small, tapered, streamlined animals showing eyes, a brain, pharyngeal arches, a notochord, and rudimentary vertebrae. Vertebrates appear to have radiated in the late Ordovician, about 450 million years ago. However, most Ordovician fossil fossil vertebrates are rare and fragmentary, although available material suggests that ancestors of the sharks and jawed fish were present along with various lineages of armored jawless fish. By the middle Silurian, about 400 million years ago, the picture is clearer: the armored jawless fish were quite diverse, and the first definite jawed fish had appeared -- the Silurian is sometimes called the "Age of Fishes." By the late Devonian, 360 million years ago, early cartilaginous fish and bony fish were diversifying. The late Devonian also marked the first tetrapods -- vertebrates with true legs that could walk on land. By about 330 million years ago, in the Mississippian, several groups of land-dwelling amphibians had appeared. The oldest known amniotes -- close to the ancestry of all reptiles, birds, and mammals -- appeared in the early Pennsylvanian, about 310 million years ago. Land amniotes continued to diversify, and by the middle Pennsylvanian had split into several taxa, two of which would go on to dominate the Mesozoic and Cenozoic: the diapsids and the synapsids.
All reptiles except turtles (incl dinos and birds)diapsids evolved into many shapes, occupying many different ecological niches since they first came onto the scene in the late Carboniferous period (roughly 350 million years ago), when they were represented by the earliest diapsid, the tiny lizardlike Petrolacosaurus
Synapsid classification has undergone tremendous change in recent years; most of the traditional groupings have been discovered to be paraphyletic. To represent this, we have used multiple lines drawn to paraphyletic groups in the cladogram above. Except for the Mammalia, all synapsid groups are extinct.
Current hypotheses about early synapsid diversification suggest that "pelycosaurs" are the basal-most synapsids, and are certainly paraphyletic. This group includes familiar "sail-back" critters like Dimetrodon, but also includes a variety of lesser known early synapsids, such as the herbivorous Caseidae. All groups of pelycosaurs went extinct by the end of the Permian. The remaining groups in the above cladogram constitute the Therapsida, and most of them diversified in the Permian or Triassic -- and then disappeared as the dinosaurs came to dominate the terrestrial world.

III. dictionary.com
the·rap·sid /θəˈræpsɪd/ Pronunciation Key - Show Spelled Pronunciation[thuh-rap-sid] Pronunciation
Key - Show IPA Pronunciation –noun 1. any of various groups of mammallike reptiles of the extinct order Therapsida, inhabiting all continents from mid-Permian to late Triassic times, some of which were probably warm-blooded and directly ancestral to mammals. –adjective 2. of or pertaining to the Therapsida.
--------------------------------------------------------------------------------
[Origin: < NL Therapsida (1905), equiv. to Gk thér- (s. of thr wild beast) + apsid- (s. of apsís arch, vault, referring to the temporal arch of the skull) + NL -a neut. pl. ending (see -a1)]
sauropod (sôr'ə-pŏd') Pronunciation Key One of the two types of saurischian dinosaurs, widespread during the Jurassic and Cretaceous Periods.
Sauropods were plant-eaters and often grew to tremendous size, having a stout body with thick legs, long slender necks with a small head, and long tails. Sauropods included the apatosaurus (brontosaurus) and brachiosaurus. Compare theropod.
theropod
noun any of numerous carnivorous dinosaurs of the Triassic to Cretaceous with short forelimbs that walked or ran on strong hind legs WordNet® 3.0, © 2006 by Princeton University. The American Heritage Science Dictionary - Cite This Source - Share This theropod (thîr'ə-pŏd')
Pronunciation Key Any of various carnivorous saurischian dinosaurs of the group Theropoda. Theropods walked on two legs and had small forelimbs and a large skull with long jaws and sharp teeth. Most theropods were of small or medium size, but some grew very large, like Tyrannosaurus. Theropods lived throughout the Mesozoic
Era. Compare sauropod.
ac·ti·nop·te·ryg·i·an /ˌæktəˌnɒptəˈrɪdʒiən/ Pronunciation Key - Show Spelled ronunciation[ak-tuh-nop-tuh-rij-ee-uhn] Pronunciation Key - Show IPA Pronunciation –adjective 1. belonging or pertaining to the Actinopterygii, a group of bony fishes. –noun 2. an actinopterygian fish.
--------------------------------------------------------------------------------
[Origin: < NL Actinopterygi(i) (pl.) (actino- actino- + Gk pterýgi(on) fin, equiv. to pteryg- (s. of ptéryx wing) + -ion dim. suffix) + -an]
sarcopterygian (sär-kŏp'tə-rĭj'ē-ən) Pronunciation Key See lobe-finned fish.
Sarcopterygii (from Greek sarx, flesh, and pteryx, fin) is traditionally the class of lobe-finned fishes, consisting of lungfish and coelacanths.
CharacteristicsThese are bony fish with paired rounded fins. These fins, being similar to limbs, suggest that these fish may be ancestors of land vertebrates.Most taxonomists who subscribe to the cladistic approach include the grouping Tetrapoda within this group, which in turns consists of all species of four-limbed vertebrates. The fin-limbs of sarcopterygiians show such a strong similarity to the expected ancestral form of tetrapod limbs that they have been universally considered the direct ancestors of tetrapods in the scientific literature.
Evolution of Sarcopterygii
Sarcopterygians belong to Osteichthyes group or bony fishes, characterized by their bony skeleton instead of cartilage. The oldest Sarcopterygians were found in the Uppermost Silurian. The first Sarcopterygian closely resembled Acanthodians. The Sarcopterygians closest relatives were the Actinopterygians - ray-finned fishes. Sarcopterygians probably evolved in the oceans, but they later came into freshwater habitats to avoid the predatory placoderms - which were dominant in the Early - Middle Devonian seas.
As Sarcopterygians evolve in the Early Devonian, the line splits into two main lineages - the Coelacanths, and the Rhipidistia. The Coelacanths appeared in the Early Devonian, and stayed in the oceans; the coelacanths' heyday was the Late Devonian and Carboniferous, as they were more common during those periods than in any other period in the Phanerozoic. Coelacanths still live today in the oceans. Rhipidistians appeared about the same time as the Coelacanths, but unlike them, Rhipidistians left the ocean world and migrated into the freshwater habitats, their ancestors probably lived in the oceans near the river mouths (estuaries). The Rhipidistians in turn split into two major groups - the lungfishes, and the tetrapodomorphs. The lungfishes' greatest diversity was in the Triassic Period, but today, there are fewer than a dozen genera left. The lungfishes evolved the first proto-lungs and proto-limbs. The lungfishes, ancient and modern, used their stubby fins (proto-limbs) to walk on land and find new water if their waterhole was depleted, and used their lungs to breathe air and get sufficient oxygen. The tetrapodomorphs have the same identical anatomy as the lungfishes, who were their closest kin, but the tetrapodomorphs appear to have stayed in water a little longer until the Late Devonian. Tetrapods - four legged vertebrates were the terapodomorphs' descendants. Tetrapods appeared in the Late Devonian epoch. Non-tetrapod sarcopterygians continued to towards the end of Paleozoic Era. They suffered heavy losses during the Permian-Triassic extinction event.

tel·e·ost (těl'ē-ŏst', tē'lē-) Pronunciation Key adj. Of or belonging to the Teleostei or Teleostomi, a large group of fishes with bony skeletons, including most common fishes. The teleosts are distinct from the cartilaginous fishes such as sharks, rays, and skates.
n. A teleost fish.
[From New Latin Teleosteī, group name (Greek teleos, complete; see teleology + osteon, bone; see ost- in Indo-European roots) and from New Latin Teleostomī, group name (Greek teleos, complete + Greek stoma, mouth).]

Animalia

animalia-notocord-nerve cord-visceral (pharyngeal, gill) clefts or arches

Craniata fossils (fm tolweb)

fossilsCraniata

hagfish (Myxinikela)330mya late Clamprey (Mayomyzon, Hardistiella, Pipiscius) lateC of USA

anaspids? or lampreys-Jamoytius (Early Silurian of Scotland)-Euphanerops (Late Devonian of Canada)

Euconodonts (Middle Cambrian (540 million years) to the Late Triassic (230 million years);Carboniferous of Scotland; Ordovician of South Africa.)

Pteraspidomorphi, or pteraspidomorphs, is a group of fossil jawless vertebrates Early Ordovician to the Late Devonian (i.e. from 470 to 370 million years ago

The Anaspida, or anaspids, are a group of fossil, jawless vertebrates which lived in the Silurian (-430 to -410 million years ago)

The Galeaspida, or galeaspids, are a highly diversified group of fossil, armored, jawless vertebrates, which lived in Silurian and Devonian times (430 to 370 million years ago).

The Pituriaspida are a small group of fossil, armored jawless vertebrates, only known by two genera, Pituriaspis and Neeyambaspis, from the late Early Devonian or early Middle Devonian (about 390 million years) of Queensland, Australia

The Gnathostomata, or gnathostomes, are the majority of the Middle Devonian (-380 million years ago) to Recent vertebrates. Extant gnathostomes fall into two major clades, the Chondrichthyes and Osteichthyes. In addition, there are two extinct major gnathostome clades, the Placodermi (Early Silurian-Late Devonian) and the Acanthodii (Latest Ordovician or Earliest Silurian - Early Permian).

The oldest known skeletal remains of terrestrial vertebrates were found in the Upper Devonian of East Greenland (Clack, 1994). The presence of Lower to Middle Devonian trackways in Australia has led to suggestions that this group may have originated in the Lower Devonian, at least 400 million years ago

Tetrapods originated no later than the Mississippian (about 350 million years ago), the period from which the oldest known relatives of living amphibians are known.

The oldest amniotes currently known date from the Middle Pennsylvanian locality known as Joggins, in Nova Scotia (Carroll, 1964). The relationships of these fossils indicate that amniotes first diverged into two lines, one line (Synapsida) that culminated in living mammals, and another line (Sauropsida) that embraces all the living reptiles (including birds). ... suggests that the more inclusive clade of which turtles (Testudines) are part (Anapsida) in most
morphological phylogenies had diverged as well, even though its current record extends back only to the Lower Permian (Laurin & Reisz, 1995).

Craniata (from TolWeb)

Chordata
-Craniata
=Hyperotreti
=Vertebrata
Gnathostomata (jawed vertebrates)
-Teleostomi
-Osteichthyes
=Sarcopterygii (lobe fin fishes & 4-legged vertebrates)
=Actinopterygii (ray fin fishes)
-Chondrichthyes (sharks rays sawfishes chimeras)


Craniata: all fishes (incl jawless) amphibians reptiles birds and mammals

Tectonic Plates (from Wiki)

List of Plates from wiki

[edit] Major plates
African Plate
Antarctic Plate
Arabian Plate
Australian Plate
Caribbean Plate
Cocos Plate
Eurasian Plate
Indian Plate
Juan de Fuca Plate
Nazca Plate
North American Plate
Pacific Plate
Philippine Plate
Scotia Plate
South American Plate

[edit] Minor plates
Aegean Sea Plate
Altiplano Plate
Amurian Plate
Anatolian Plate
Balmoral Reef Plate
Banda Sea Plate
Bird's Head Plate
Burma Plate
Caroline Plate
Conway Reef Plate
Easter Plate
Futuna Plate
Galapagos Plate
Hellenic Plate
Iranian Plate
Juan Fernandez Plate
Kermadec Plate
Manus Plate
Maoke Plate
Mariana Plate
Molucca Sea Plate
New Hebrides Plate
Niuafo'ou Plate
North Andes Plate
North Bismarck Plate
Okhotsk Plate
Okinawa Plate
Panama Plate
Rivera Plate
Sandwich Plate
Shetland Plate
Solomon Sea Plate
Somali Plate
South Bismarck Plate
Sunda Plate
Timor Plate
Tonga Plate
Woodlark Plate
Yangtze Plate

[edit] Plates within orogens
Some models identify more minor plates within current orogens.
Apulian plate
Explorer Plate
Gorda Plate

[edit] Ancient plates
Baltic Plate
Bellingshausen Plate
Charcot Plate
Cimmerian Plate
Farallon Plate
Insular Plate
Intermontane Plate
Izanagi Plate
Kula Plate
Lhasa Plate
Moa Plate
Phoenix Plate

More on mammals (Wiki)

The McKenna/Bell hierarchical listing of all of the terms used for mammal groups above the species includes extinct mammals as well as modern groups, and introduces some fine distinctions such as legions and sublegions (ranks which fall between classes and orders) that are likely to be glossed over by the nonprofessionals.
The published re-classification forms both a comprehensive and authoritative record of approved names and classifications and a list of invalid names.
Extinct groups are represented by a cross (†).
Class Mammalia
Subclass Prototheria: monotremes: echidnas and the Platypus
Subclass Theriiformes: live-bearing mammals and their prehistoric relatives
Infraclass †Allotheria: multituberculates
Infraclass †Triconodonta: triconodonts
Infraclass Holotheria: modern live-bearing mammals and their prehistoric relatives
Supercohort Theria: live-bearing mammals
Cohort Marsupialia: marsupials
Magnorder Australidelphia: Australian marsupials and the Monito del Monte
Magnorder Ameridelphia: New World marsupials
Cohort Placentalia: placentals
Magnorder Xenarthra: xenarthrans
Magnorder Epitheria: epitheres
Grandorder Anagalida: lagomorphs, rodents, and elephant shrews
Grandorder Ferae: carnivorans, pangolins, †creodonts, and relatives
Grandorder Lipotyphla: insectivorans
Grandorder Archonta: bats, primates, colugos, and treeshrews
Grandorder Ungulata: ungulates
Order Tubulidentata incertae sedis: aardvark
Mirorder Eparctocyona: †condylarths, whales, and artiodactyls (even-toed ungulates)
Mirorder †Meridiungulata: South American ungulates
Mirorder Altungulata: perissodactyls (odd-toed ungulates), elephants, manatees, and hyraxes


Molecular classification of placentals
Clade Atlantogenata
Group I: Afrotheria
Clade Afroinsectiphilia
Order Macroscelidea: elephant shrews (Africa)
Order Afrosoricida: tenrecs and golden moles (Africa)
Order Tubulidentata: aardvark (Africa south of the Sahara)
Clade Paenungulata
Order Hyracoidea: hyraxes or dassies (Africa, Arabia)
Order Proboscidea: elephants (Africa, Southeast Asia)
Order Sirenia: dugong and manatees (cosmopolitan tropical)
Group II: Xenarthra
Order Pilosa: sloths and anteaters (Neotropical)
Order Cingulata: armadillos (Americas)
Clade Boreoeutheria
Group III: Euarchontoglires (Supraprimates)
Superorder Euarchonta
Order Scandentia: treeshrews (Southeast Asia).
Order Dermoptera: flying lemurs or colugos (Southeast Asia)
Order Primates: lemurs, bushbabies, monkeys, apes (cosmopolitan)
Superorder Glires
Order Lagomorpha: pikas, rabbits, hares (Eurasia, Africa, Americas)
Order Rodentia: rodents (cosmopolitan)
Group IV: Laurasiatheria
Order Erinaceomorpha: hedgehogs
Order Soricomorpha: moles, shrews, solenodons
Order Chiroptera: bats (cosmopolitan)
Clade Cetartiodactyla
Order Cetacea: whales, dolphins and porpoises
Order Artiodactyla: even-toed ungulates, including pigs, hippopotamus, camels, giraffe, deer, antelope, cattle, sheep, goats
Order Perissodactyla: odd-toed ungulates, including horses, donkeys, zebras, tapirs, and rhinoceroses
Clade Ferae
Order Pholidota: pangolins or scaly anteaters (Africa, South Asia)
Order Carnivora: carnivores (cosmopolitan)

Mammalia (from Wikipedia)

A somewhat standardized classification system has been adopted by most current mammalogy classroom textbooks. The following taxonomy of extant and recently extinct mammals is from Vaughan et al. (2000).

Class Mammalia
Subclass Prototheria: monotremes: platypuses and echidnas
Subclass Theria: live-bearing mammals
Infraclass Metatheria: marsupials
Infraclass Eutheria: placentals


1 Subclass Theria
1.1 Infraclass Eutheria (Placental Mammals)
1.1.1 Order Afrosoricida (tenrecs and golden moles)
1.1.2 Order Macroscelidea
1.1.3 Order Tubulidentata
1.1.4 Order Hyracoidea
1.1.5 Order Proboscidea
1.1.6 Order Sirenia
1.1.7 Order Cingulata (Armadillos)
1.1.8 Order Pilosa (Anteaters, and Sloths)
1.1.9 Order Scandentia (Treeshrews)
1.1.10 Order Dermoptera (Colugos)
1.1.11 Order Primates
1.1.12 Order Rodentia
1.1.13 Order Lagomorpha
1.1.14 Order Erinaceomorpha
1.1.15 Order Soricomorpha
1.1.16 Order Chiroptera (Bats)
1.1.17 Order Pholidota
1.1.18 Order Cetacea
1.1.19 Order Carnivora
1.1.20 Order Perissodactyla
1.1.21 Order Artiodactyla

1 Subclass Prototheria (the monotremes)
1.1 Order Monotremata (monotremes, egg-laying mammals)

2 Subclass Theria
2.1 Infraclass Metatheria (marsupials)
2.1.1 Order Didelphimorphia (American opossums)
2.1.2 Order Paucituberculata (shrew opossums)
2.1.3 Order Microbiotheria (Monito del Monte)
2.1.4 Order Notoryctemorphia (marsupial moles)
2.1.5 Order Dasyuromorphia (marsupial carnivores)
2.1.6 Order Peramelemorphia (bandicoots and bilbies)
2.1.7 Order Diprotodontia (diprotodont marsupials)
2.1.7.1 Suborder Vombatiformes (wombats and koalas)
2.1.7.2 Suborder Phalangeriformes (possums and gliders)
2.1.7.3 Suborder Macropodiformes (kangaroos, wallaroos, wallabies

Lakatos quotes

Thus the crucial element in falsificationism is whether the new theory offers any novel, excess information compared with its predecessor and whether some of this excess information is corroborated. Justificationists valued 'confirming' instances of a theory; naive falsificationists stressed 'refuting' instances; for the methodological falsificationists it is the—rather rare—corroborating instances of the excess information which are the crucial ones; these receive all the attention.
***********
Again, for the naive falsificationist a theory is falsified by a "(fortified) observational" statement which conflicts with it (or rather, which he decides to interpret as conflicting with it). The sophisticated falsificationist regards a scientific theory T as falsified if and only if another theory T' has been proposed with the following characteristics: (1) T' has excess empirical content over T: that is, it predicts novel facts, that is, facts improbable in the light of, or even forbidden, by T,[4] (2) T' explains the previous success of T, that is, all the unrefuted content of T is contained (within the limits of observational error) in the content of T'; and (3) some of the excess content of T' is corroborated.[5] …
I used "prediction" in a wide sense that includes "postdiction."

tiger from Wikipedia 21Feb2008

Tiger
Animalia Kingdom
Chordata Phylum
Mammalia Class
Carnivora Order
Feliformia Sub-Order [other: Caniformia}
Felidae Family [other: Hyaenidae, etc.}
Panthera Genus
P. tigris


hominoid Hominoidea superfamily (lesser apes - gibbons- and great apes)
hominid Hominidae family (great apes)
hominine Homininae subfamily (gorillas, chimps, humans- not orangutans)
hominin Hominini tribe (chimps and humans)
hominan Hominina sub-tribe (humans & extinct relatives)
human

Human
Animalia
Chordata
Mammalia
Primate
Hominidae
HomoH. sapiens
H.s. sapiens

taken from Wikipedia 21Feb2008

Neomura is a speculative clade composed of the two domains of Archaea and Eukarya. The group was first proposed by Thomas Cavalier-Smith and its name means "new walls"; so called because it is thought to have evolved from Bacteria, and one of the major changes of this evolution was the replacement of peptidoglycan cell walls with other glycoproteins. The adjectival form is Neomuran, and a single individual from the group is called a Neomuran.

Animals, plants, fungi, and protists are eukaryotes (IPA: /ju?'kær??t/), organisms whose cells are organized into complex structures by internal membranes. The most characteristic membrane-bound structure is the nucleus. The presence of a nucleus gives these organisms their name: which comes from the Greek e?, meaning good/true, and ??????, meaning nut, referring to the nucleus. Many eukaryotic cells contain other membrane-bound organelles such as mitochondria, chloroplasts and Golgi bodies. Eukaryotes often have unique flagella made of microtubules in a 9+2 arrangement.
Cell division in eukaryotes is also different from organisms without a nucleus. This process involves separating the duplicated chromosomes, through movements directed by microtubules. There are two types of these division processes. In mitosis, one cell divides to produce two genetically-identical cells. In meiosis, which is required in sexual reproduction, one diploid cell (having two copies of each chromosome, one from each parent) undergoes a process of recombination between each pair of parental chromosomes, and then two stages of cell division, resulting in four haploid cells (gametes), each of which has only a single complement of chromosomes, each one being a unique mix and match of the corresponding pair of parental chromosomes.
Eukaryotes appear to be monophyletic, and thus make up one of the three domains of life. The two other domains, bacteria and archaea (prokaryotes (without a nucleus)), share none of the previously-described features, though the eukaryotes do share some aspects of their biochemistry with the archaea, and, as such, are grouped with the archaea in the clade Neomura.

Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan becomes fixed as they develop, usually early on in their development as embryos, although some undergo a process of metamorphosis later on in their life. Most animals are motile - they can move spontaneously and independently. Animals are heterotrophs - they are dependent on other organisms (e.g. plants) for sustenance.
Most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago.
Eumetazoa is a clade comprising all major animal groups except sponges. Characteristics of eumetazoans include true tissues organized into germ layers, and an embryo that goes through a gastrula stage. The clade is usually held to contain at least Ctenophora, Cnidaria, and Bilateria. Whether mesozoans and placozoans belong is in dispute.

The Bilateria are all animals having a bilateral symmetry, i.e. they have a front and a back end, as well as an upside and downside. Radially symmetrical animals like jellyfish have a topside and downside, but no front and back. The bilateralians are a subregnum (a major group) of animals, including the majority of phyla; the most notable exceptions are the sponges and cnidarians. For the most part, Bilateria have bodies that develop from three different germ layers, called the endoderm, mesoderm, and ectoderm. From this they are called triploblastic. Nearly all are bilaterally symmetrical, or approximately so. The most notable exception is the echinoderms, which are radially symmetrical as adults, but are bilaterally symmetrical as larvae.
Except for a few primitive forms, the Bilateria have complete digestive tracts with separate mouth and anus. Most Bilateria also have a type of internal body cavity, called a coelom. It was previously thought that acoelomates gave rise to the other group, but there is some evidence now that in the main acoelomate phyla (flatworms and gastrotrichs) the absence could be secondary. The indirect evidence for the primitivity of the coelom is that the oldest known bilaterian animal, Vernanimalcula, had a structure that could be interpreted as a body cavity.

Kingdom: Animalia
Subkingdom: Eumetazoa (unranked)
Bilateria Hatschek, 1888
Phyla Orthonectida Rhombozoa Acoelomorpha Chaetognatha
Superphylum Deuterostomia Chordata Hemichordata Echinodermata Xenoturbellida Vetulicolia †
Superphylum Ecdysozoa Kinorhyncha Loricifera Priapulida Nematoda Nematomorpha Lobopodia † Onychophora Tardigrada Arthropoda
Superphylum Platyzoa Platyhelminthes Gastrotricha Rotifera Acanthocephala Gnathostomulida Micrognathozoa Cycliophora
Superphylum Lophotrochozoa Sipuncula Hyolitha † Nemertea Phoronida Bryozoa Entoprocta Brachiopoda Mollusca Annelida Echiura

Deuterostomes (taxonomic term: Deuterostomia; from the Greek: "second mouth") are a superphylum of animals. They are a subtaxon of the Bilateria branch of the subregnum Eumetazoa, and are opposed to the protostomes. Deuterostomes are distinguished by their embryonic development; in deuterostomes, the first opening (the blastopore) becomes the anus, while in protostomes it becomes the mouth.
There are four living phyla of deuterostomes:
Phylum Chordata (vertebrates and their kin) Phylum Echinodermata (starfishes, sea urchins, sea cucumbers, etc.) Phylum Hemichordata (acorn worms and possibly graptolites) Phylum Xenoturbellida (2 species of worm-like animals)

Protostomes (from the Greek: mouth first) are a taxon of animals. Together with the deuterostomes and a few smaller phyla, they make up the Bilateria, mostly comprising animals with bilateral symmetry and three germ layers. The major distinctions between deuterostomes and protostomes are found in embryonic development. In protostome development, the first opening in development, the blastopore, becomes the animal's mouth. In deuterostome development, the blastopore becomes the animal's anus. Protostomes have what is known as spiral cleavage which is determinate, meaning that the fate of the cells is determined as they are formed. This is in contrast to deuterostomes which have radial cleavage that is indeterminate.
Another contrast resides in the formation of the coelom. Protostomes are schizocoelomates, meaning a solid mass of the embryonic mesoderm splits to form a coelom. Deuterostomes are enterocoelous, meaning the folds of the archenteron form the coelom.
Current molecular data suggest that protostome animals can be divided into three major groups as follows: [ ?Ecdysozoa, Lophotrochozoa, Platyzoa?]
Nematoda, e.g. nematodes roundworms Mollusca, e.g. molluscs, snails, slugs, clams, octopus, squid Platyhelminthes, e.g. flatworms Arthropoda, e.g. spiders, insects, crustaceans Annelida, e.g. segmented worms, earthworms, leeches Of these, the latter two make up the Spiralia, including most animals where the embryo undergoes spiral cleavage.

The Ecdysozoa are a group of protostome animals, including the Arthropoda (insects, arachnids, crustaceans, et cetera), Nematoda, and several smaller phyla. They were first defined by Aguinaldo et al. in 1997, based mainly on trees constructed using 18S ribosomal RNA genes.[1] The group is also supported by morphological characters, and can be considered as including all animals that shed their exoskeleton (see ecdysis). Groups corresponding roughly to the Ecdysozoa had been proposed previously by Perrier in 1897 and Seurat in 1920 based on morphology alone.

The Lophotrochozoa ("crest-bearing animals") are one of two or three major groups of protostome animals. The taxon was introduced in the 1990s as a result of studies of the evolution of small-subunit ribosomal RNA (rRNA) supporting the monophyly of the phyla listed in the infobox shown at right.[1]
Trochozoans produce trochophore larvae, which have two bands of cilia around their middle. Previously these were treated together as the Trochozoa, together with the arthropods, which do not produce trochophore larvae but were considered close relatives of the annelids because they are both segmented. However, they show a number of important differences, and the arthropods are now placed separately among the Ecdysozoa.
The Lophophorata are united by the presence of a lophophore, a fan of ciliated tentacles surrounding the mouth, and so were treated together as the lophophorates. They are unusual in showing radial cleavage, and some authors considered them deuterostomes, before RNA trees placed them together with the trochozoans. The exact relationships between the different phyla are not entirely certain. However, it appears that neither the lophophorates nor the Trochozoa are monophyletic groups by themselves, but are mixed together.
Other phyla are included on the basis of molecular data.

The Platyzoa are a group of protostome animals proposed by Thomas Cavalier-Smith in 1998. Cavalier-Smith included in Platyzoa the Phylum Platyhelminthes or flatworms, and a new phylum, Acanthognatha, into which he gathered several previously described phyla of microscopic animals. Subsequent studies have supported Platyzoa as a clade, a monophyletic group of organisms with a common ancestor, while differing on the phyla included and on relationships within Platyzoa.
One current scheme places the following traditional phyla in Platyzoa:
Platyhelminthes Gastrotricha Gnathifera Rotifera Acanthocephala Gnathostomulida Micrognathozoa Cycliophora The Platyhelminthes and Gastrotricha are acoelomate. The other phyla have a pseudocoel, and share characteristics such as the structure of their jaws and pharynx, although these have been secondarily lost in the parasitic Acanthocephala. They form a monophyletic subgroup called the Gnathifera.
The Platyzoa are close relatives of the Lophotrochozoa, and are sometimes included in that group. Together the two make up the Spiralia.