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55-558: Redlichiida is an order of trilobites , a group of extinct marine arthropods . Species assigned to the order Redlichiida are among the first trilobites to appear in the fossil record, about halfway during the Lower Cambrian. Due to the difficulty to relate sediments in different areas, there remains some discussion, but among the earliest are Fallotaspis (suborder Olenellina), and Lemdadella (suborder Redlichiina), both belonging to this order. The first representatives of

110-609: A passive margin . Sedimentary rocks that were deposited on top of the basement complex were formed in a setting of quiet marine and river waters. The craton was covered by shallow, warm, tropical epicontinental or epicratonic sea (meaning literally "on the craton") that had maximum depths of only about 60 m (200 ft) at the shelf edge. The position of the equator during the Late Ordovician epoch ( c.  458  – c.   444 Ma) on Laurentia has been determined via extensive shell bed records. Flooding of

165-571: A metamorphosis at any stage. Two major Lagerstätten where redlichiids are found are the Emu Bay shales of Southern Australia and the Maotianshan shales near Chengjiang in China. Other regions include Morocco, Labrador, Canada, the western United States , and Bohemia , Czech Republic . The appendages have been preserved in a few specimens. They follow typical trilobite patterns in terms of

220-633: A network of early Proterozoic orogenic belts . Small microcontinents and oceanic islands collided with and sutured onto the ever-growing Laurentia, and together formed the stable Precambrian craton seen today. The craton is named after the Laurentian Shield , through the Laurentian Mountains , which received their name from the St. Lawrence River , named after Saint Lawrence of Rome. In eastern and central Canada, much of

275-427: A taxonomist needs to follow in describing or recognizing an order. Some taxa are accepted almost universally, while others are recognized only rarely. The name of an order is usually written with a capital letter. For some groups of organisms, their orders may follow consistent naming schemes . Orders of plants , fungi , and algae use the suffix -ales (e.g. Dictyotales ). Orders of birds and fishes use

330-788: Is more common, not least because large parts of the structure extend outside Canada. In the United States, the craton bedrock is covered with sedimentary rocks on the broad interior platform in the Midwest and Great Plains regions and is exposed only in northern Minnesota, Wisconsin, the New York Adirondacks , and the Upper Peninsula of Michigan . The sequence of sedimentary rocks varies from about 1,000 m to in excess of 6,100 m (3,500–20,000 ft) in thickness. The cratonic rocks are metamorphic or igneous with

385-575: Is part of Laurentia. The island is separated from North America by the Nares Strait , but this is a Pleistocene erosional feature. The strait is floored with continental crust and shows no indications of a thermal event or seaway tectonism. Greenland is composed mostly of crust of Archean to Proterozoic age, with lower Paleocene shelf formations on its northern margin and Devonian to Paleogene formations on its western and eastern margins. The eastern and northern margins were heavily deformed during

440-659: The Prodromus Systematis Naturalis Regni Vegetabilis of Augustin Pyramus de Candolle and the Genera Plantarum of Bentham & Hooker, it indicated taxa that are now given the rank of family (see ordo naturalis , ' natural order '). In French botanical publications, from Michel Adanson 's Familles naturelles des plantes (1763) and until the end of the 19th century, the word famille (plural: familles )

495-632: The Basin and Range Province has been stretched up to 100% of its original width. The area experienced numerous large volcanic eruptions . Baja California rifted away from North America during the Miocene . This block of crust consists of Proterozoic to early Paleozoic shelf and Mesozoic arc volcano formations. The Holocene being an interglacial , a warm spell between episodes of extensive glaciation. Several climate events occurred in Laurentia during

550-611: The Belt Supergroup , which is over 12 kilometers (7.5 mi) thick. By 750 Ma the breakup was mostly complete, and Gondwana (composed of most of today's southern continents) had rotated away from Laurentia, which was left isolated near the equator. The breakup of Rodinia may have triggered an episode of severe ice ages (the Snowball Earth hypothesis.) There is some evidence that the fragments of Rodinia gathered into another short-lived supercontinent, Pannotia , at

605-642: The Caledonian orogeny . The Isua Greenstone Belt of western Greenland preserves oceanic crust containing sheeted dike complexes . These provide evidence to geologists that mid-ocean ridges existed 3.8 Ga. The Abitibi gold belt in the Superior Province is the largest greenstone belt in the Canadian Shield. Laurentia first assembled from six or seven large fragments of Archean crust at around 2.0 to 1.8 Gya. The assembly began when

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660-756: The Chattanooga Shale and the Antler Orogeny in the Western Cordillera. During the Carboniferous and Permian , Laurussia fused with Gondwana to form Pangaea . The resulting Alleghanian orogeny created the Central Pangean Mountains . The mountains were located close to the equator and produced a year-round zone of heavy precipitation that promoted the deposition of extensive coal beds, including

715-461: The Grenville orogeny at 1.30 to 0.95 Gya, which accreted the 1.30 to 1.00 Gya Llano-Grenville province to Laurentia. The Picuris orogeny , in particular, was characterized by the intrusion of great volumes of granitoid magma into the juvenile crust, which helped mature the crust and stitch it together. Slab rollback at 1.70 and 1.65 Gya deposited characteristic quartzite - rhyolite beds on

770-523: The Phanerozoic eon. During the late Cambrian through the Ordovician , sea level fluctuated with ice cap melt. Nine macro scale fluctuations of "global hyper warming", or high intensity greenhouse gas conditions, occurred. Due to sea level fluctuation, these intervals led to mudstone deposits on Laurentia that act as a record of events. The late Ordovician brought a cooling period, although

825-675: The Western Interior Seaway ran from the Gulf of Mexico to the Arctic Ocean , dividing North America into eastern and western land masses. From time to time, land masses or mountain chains rose up on the distant edges of the craton and then eroded down, shedding their sand across the landscape. Chalk beds of the Niobrara Formation were deposited at this time, and accretion of crustal fragments continued along

880-628: The Wopmay orogen of northwest Canada. During the assembly of the core of Laurentia, banded iron formation was deposited in Michigan, Minnesota, and Labrador. The resulting nucleus of Laurentia was mostly reworked Archean crust but with some juvenile crust in the form of volcanic arc belts. Juvenile crust is crust formed from magma freshly extracted from the Earth's mantle rather than recycled from older crustal rock. The intense mountain building of

935-687: The Appalachian coal beds in the U.S. Meanwhile, Gondwana had drifted onto the South Pole, and cycles of extensive glaciation produced a characteristic pattern of alternating marine and coal swamp beds called cyclothems . During the Pennsylvanian , the Ancestral Rocky Mountains were raised in the southwestern part of Laurentia. This has been attributed either to either the collision with Gondwana or subduction under

990-696: The Latin suffix -iformes meaning 'having the form of' (e.g. Passeriformes ), but orders of mammals and invertebrates are not so consistent (e.g. Artiodactyla , Actiniaria , Primates ). For some clades covered by the International Code of Zoological Nomenclature , several additional classifications are sometimes used, although not all of these are officially recognized. In their 1997 classification of mammals , McKenna and Bell used two extra levels between superorder and order: grandorder and mirorder . Michael Novacek (1986) inserted them at

1045-700: The Slave craton collided with the Rae-Hearne craton, and the Rae-Hearne craton collided shortly after with the Superior Craton. These then merged with several smaller fragments of Archean crust, including the Wyoming, Medicine Hat, Sask, Marshfield, and Nain blocks. This series of collisions raised the mountains of the Trans-Hudson orogenic belt , which likely were similar to the modern Himalayas , and

1100-517: The Trans-Hudson orogeny formed thick, stable roots beneath the craton, possibly by a process of "kneading" that allowed low density material to move up and high density material to move down. Over the next 900 million years, Laurentia grew by the accretion of island arcs and other juvenile crust and occasional fragments of older crust (such as the Mojave block). This accretion occurred along

1155-598: The Western Cordillera. Northeast Mexico was added to the North American craton relatively recently in geological time. This block was formed from the Mesozoic to nearly the present day, with only small fragments of earlier basement rock . It moved as a coherent unit after the breakup of Pangaea. The Atlantic and Gulf Coasts experienced eight transgressions in the Cenozoic. The Laramide orogeny continued to raise

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1210-549: The boundary between the Lower and the Middle Cambrian. Fossils of redlichiinid are associated with Cambrian regions other than Laurentia. Order (biology) What does and does not belong to each order is determined by a taxonomist , as is whether a particular order should be recognized at all. Often there is no exact agreement, with different taxonomists each taking a different position. There are no hard rules that

1265-650: The center of the craton nearly rifted apart along the Midcontinent Rift System . This produced the Keweenawan Supergroup , whose flood basalts are rich in copper ore. Laurentia was formed in a tectonically active world. The subduction under the southeast margin of the continent is thought to have contributed to the formation of Rodinia . According to the Southwest U.S. and East Antarctica or SWEAT hypothesis , Laurentia became

1320-404: The central axis, the third segment from the front may have an exta large and wide rib (a state called macropleural). The tailshield (or pygidium ) is small but appears to be composed of more than one segment. In Olenellina the earliest larval stage (called protaspis) has not been found, so it is presumed it was not calcified. The development of Redlichia from protaspis to adult was gradual without

1375-491: The continent that occurred during the Ordovician provided the shallow warm waters for the success of sea life and therefore a spike in the carbonate shells of shellfish. Today the beds are composed of fossilized shells or massive-bedded Thalassinoides facies and loose shells or nonamalgamated brachiopod shell beds. These beds imply the presence of an equatorial climate belt that was hurricane free which lay inside 10° of

1430-561: The continental margin from the southwest. Two additional marine transgressions took place during the late Paleozoic: the Kaskaskia and Absaroka. The great continental mass of Pangaea strongly affected climate patterns. The Permian was relatively arid, and evaporites were deposited in the Permian Basin . Sedimentary beds deposited in the southwest in the early Triassic were fluvial in character, but gave way to eolian beds in

1485-402: The contour at the ventral side (the so-called doublure ), a state called conterminant. The hypostomes of redlichiids have narrow borders, are not split into backward pointing forks, and have only small muscle attachment areas (or maculae). The articulate middle part of the exoskeleton (or thorax ) is composed of many of segments that often end in a spine at the side of the animal. To each side of

1540-911: The core of an independent continent with the opening of the North Atlantic in the Paleogene . Four orogenies occurred in the Mesozoic in the Western Cordillera: the Sonoma , Nevadan , Sevier , and Laramide . The Nevadan orogeny emplaced the extensive batholiths of the Sierra Nevada . The regression of the Sundance Sea in the late Jurassic was accompanied by deposition of the Morrison Formation , notable for its vertebrate fossils. During Cretaceous times,

1595-515: The core of the supercontinent . It was rotated approximately 90 degrees clockwise compared with its modern orientation, with East Antarctica and Australia to the north (what is now the west), Siberia to the east (present north), Baltica and Amazonia to the south (present east), and Congo to the southwest (present southeast). The Grenville orogen extended along the entire southwest (present southeast) margin of Laurentia, where it had collided with Congo, Amazonia, and Baltica. Laurentia lay along

1650-668: The craton. These included the North Slope of Alaska, which merged during the Early Devonian . Several small crust fragments accreted from the late Devonian through the Mesozoic to form the Western Cordillera. The Western Cordillera became a convergent plate margin during the Ordovician, and the Transcontinental Arch became submerged, only to reappear in the Devonian. The Devonian also saw the deposition of

1705-472: The ending -anae that was initiated by Armen Takhtajan 's publications from 1966 onwards. The order as a distinct rank of biological classification having its own distinctive name (and not just called a higher genus ( genus summum )) was first introduced by the German botanist Augustus Quirinus Rivinus in his classification of plants that appeared in a series of treatises in the 1690s. Carl Linnaeus

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1760-520: The equator. Recent evidence suggests that South America and Africa never quite joined to Rodinia, though they were located very close to it. Newer reconstructions place Laurentia closer to its present-day orientation, with East Antarctica and Australia to the west, South China to the northwest, Baltica to the east, and Amazonia and Rio de la Plata to the south. The breakup of Rodinia began by 780 Ma, when numerous mafic dike swarms were emplaced in western Laurentia. Early stages of rifting produced

1815-617: The equator. This ecological conclusion matches the previous paleomagnetic findings which confirms this equatorial location. At the end of the Cambrian, about 490 Mya, Avalonia rifted away from Gondwana. By the end of the Ordovician, Avalonia had merged with Baltica, and the two fused to Laurentia at the end of the Silurian (about 420 Ma) in the Caledonian orogeny . This produced the continent of Laurussia. During this time, several small continental fragments merged with other margins of

1870-910: The field of zoology , the Linnaean orders were used more consistently. That is, the orders in the zoology part of the Systema Naturae refer to natural groups. Some of his ordinal names are still in use, e.g. Lepidoptera (moths and butterflies) and Diptera (flies, mosquitoes, midges, and gnats). In virology , the International Committee on Taxonomy of Viruses 's virus classification includes fifteen taxomomic ranks to be applied for viruses , viroids and satellite nucleic acids : realm , subrealm , kingdom , subkingdom, phylum , subphylum , class, subclass, order, suborder, family, subfamily , genus, subgenus , and species. There are currently fourteen viral orders, each ending in

1925-577: The fossil record of the earliest larval stage, the protaspid, suggests that it may have been uncalcified, which would be a second unique character that distinguishes the Olenellina from all other trilobites. Fossils of olenellinid trilobites are found in North America, and other associated areas that comprised the Cambrian continent of Laurentia . They are very common and are used to define the extent of Laurentia. Their abrupt disappearance marks

1980-451: The headshield (or cephalon ) very often carries a spine, termed a genal spine. The eye lobes are sickle-shaped, long and extend from the frontal lobe of the central raised area of the cephalon (or glabella ) curving outward and increasingly backwards and sometimes eventually inwards again. The visual surface, that contains the calcite lenses is surrounded by fracture lines (or circumocular sutures ), so that it has most often broken away from

2035-527: The late Triassic. Pangaea reached its height about 250 Ma, at the start of the Triassic . The breakup of Pangaea began in the Triassic, with rifting along what is now the east coast of the U.S. that produced red beds , arkosic sandstone , and lake shale deposits. The central Atlantic ocean basin began opening at about 180 Ma. Florida, which had been a part of Gondwana before the assembly of Pangaea,

2090-652: The middle Silurian . During the early to middle Ordovician , several volcanic arcs collided with Laurentia along what is now the Atlantic coast of North America. This caused an episode of mountain-building called the Taconic orogeny . As the mountains raised by the Taconic orogeny were subsequently eroded, they produced the immense Queenston Delta , recorded in the rocks of the Queenston Formation . There

2145-528: The number, placement, and types of legs, antennae, gills , etc. The order Redlichiida is divided into two suborders : Olenellina and Redlichiina . The main difference between the two groups is the lack of facial sutures in the Olenellina. This absence of the facial sutures is regarded as primitive by most scholars. Opisthoparian facial sutures are a shared character of all Redlichiina. In other trilobites, dorsal sutures may be opisthoparian, gonatoparian, proparian or they may be lost secondarily. The absence in

2200-548: The orders Corynexochida and Ptychopariida also appear very early on and may prove to be even earlier than any redlichiid species. In terms of anatomical comparison, the earliest redlichiid species are probably ancestral to all other trilobite orders and share many primitive characters. The last redlichiid trilobites died out before the end of the Middle Cambrian. Most redlichiids are rather flat (or have low dorso–ventral convexity) and their exoskeleton typically has an oval outline, about 1½× longer than wide. Each back edge of

2255-626: The overlying sedimentary layers composed mostly of limestones , sandstones , and shales . These sedimentary rocks were largely deposited 650–290 Ma. The oldest bedrock, assigned to the Archean Slave , Rae , Hearne , Wyoming , Superior , and Nain Provinces, is located in the northern two thirds of Laurentia. During the Early Proterozoic they were covered by sediments, most of which has now been eroded away. Greenland

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2310-745: The present Rocky Mountains into the Paleocene. The Western Cordillera continued to suffer tectonic deformation, including the formation of the Basin and Range Province in the middle Cenozoic and the uplift of the Colorado Plateau . The Colorado Plateau was uplifted with remarkably little deformation. The flood basalts of the Columbia Plateau also erupted during the Cenozoic. The southwestern portion of Laurentia consists of Precambrian basement rocks deformed by continental collisions. This area has been subjected to considerable rifting as

2365-428: The rest of the cephalon. The glabella tapers forward and is relatively long, with the frontal lobe boss-like or pointy, followed by three rings or pairs of lobes (defined by furrows that may or may not cross over the midline), and finally at the back of the cephalon the so-called occipital ring. On the ventral side of the cephalon, the palate (or hypostome ) is attached to the part of the calcified exoskeleton that defines

2420-420: The same position. Michael Benton (2005) inserted them between superorder and magnorder instead. This position was adopted by Systema Naturae 2000 and others. In botany , the ranks of subclass and suborder are secondary ranks pre-defined as respectively above and below the rank of order. Any number of further ranks can be used as long as they are clearly defined. The superorder rank is commonly used, with

2475-624: The southeastern margin of Laurentia, where there was a long-lived convergent plate boundary . Major accretion episodes included the Yavapai orogeny at 1.71 to 1.68 Gya, which welded the 1.8 to 1.7 Gya Yavapai province to Laurentia; the Mazatzal orogeny at 1.65 to 1.60 Gya, accreting the 1.71 to 1.65 Gya Mazatzal province; the Picuris orogeny at 1.49 to 1.45 Gya, which may have welded the 1.50 to 1.30 Gya Granite-Rhyolite province to Laurentia; and

2530-476: The southern margin of the craton. This long episode of accretion doubled the size of Laurentia but produced craton underlain by relatively weak, hydrous, and fertile (ripe for extraction of magma) mantle lithosphere. The subduction under the southeast margin of the continent likely caused enrichment of the lithospheric mantle beneath the orogenic belts of the Grenville Province . Around 1.1 Gya,

2585-666: The stable craton is exposed at the surface as the Canadian Shield , an area of Precambrian rock covering over a million square miles. This includes some of the oldest rock on Earth, such as the Archean rock of the Acasta Gneiss , which is 4.04 billion years ( Ga ) old, and the Istaq Gneiss Complex of Greenland, which is 3.8 Ga. When subsurface extensions are considered, the wider term Laurentian Shield

2640-572: The suffix -virales . Laurentia Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America . Many times in its past, Laurentia has been a separate continent , as it is now in the form of North America, although originally it also included the cratonic areas of Greenland and the Hebridean Terrane in northwest Scotland . During other times in its past, Laurentia has been part of larger continents and supercontinents and consists of many smaller terranes assembled on

2695-544: The very end of the Proterozoic. This continent broke up again almost at once, and Laurentia rifted away from South America at around 565 Ma to once again become an isolated continent near the equator, separated from Gondwana by the western Iapetus Ocean . Sometime in the early Cambrian , around 530 Ma, Argentina rifted away from Laurentia and accreted onto Gondwana. The breakup of Pannotia produced six major continents: Laurentia, Baltica, Kazakhstania, Siberia, China, and Gondwana. Laurentia remained an independent continent until

2750-525: The word family ( familia ) was assigned to the rank indicated by the French famille , while order ( ordo ) was reserved for a higher rank, for what in the 19th century had often been named a cohors (plural cohortes ). Some of the plant families still retain the names of Linnaean "natural orders" or even the names of pre-Linnaean natural groups recognized by Linnaeus as orders in his natural classification (e.g. Palmae or Labiatae ). Such names are known as descriptive family names. In

2805-429: Was also violent volcanic activity, including the eruption that produced the Millburg/Big Bentonite ash bed. About 1,140 cubic kilometers (270 cu mi) of ash erupted in this event. However, this does not seem to have triggered any mass extinction. Throughout the early Paleozoic, Laurentia was characterized by a tectonically stable interior flooded by the seas, with marginal orogenic belts . An important feature

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2860-457: Was left with Laurentia during the opening of the central Atlantic. This former Gondwana fragment includes the Carolina Slate belt and parts of Alabama. The Gulf of Mexico opened during the Late Triassic and Jurassic. This was accompanied by deposition of evaporite beds that later gave rise to salt domes that are important petroleum reservoirs today. Europe rifted away from North America between 140 and 120 Ma, and Laurentia once again became

2915-400: Was the Transcontinental Arch, which ran southwest from the lowlands of the Canadian Shield. The shield and the arch were the only portions of the continent that were above water through much of the early Paleozoic. There were two major marine transgressions (episodes of continental flooding) during the early Paleozoic, the Sauk and the Tippecanoe. During this time, the Western Cordillera was

2970-485: Was the first to apply it consistently to the division of all three kingdoms of nature (then minerals , plants , and animals ) in his Systema Naturae (1735, 1st. Ed.). For plants, Linnaeus' orders in the Systema Naturae and the Species Plantarum were strictly artificial, introduced to subdivide the artificial classes into more comprehensible smaller groups. When the word ordo was first consistently used for natural units of plants, in 19th-century works such as

3025-409: Was used as a French equivalent for this Latin ordo . This equivalence was explicitly stated in the Alphonse Pyramus de Candolle 's Lois de la nomenclature botanique (1868), the precursor of the currently used International Code of Nomenclature for algae, fungi, and plants . In the first international Rules of botanical nomenclature from the International Botanical Congress of 1905,

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