Misplaced Pages

#829170

27-665: Olenellina is a suborder of the order Redlichiida of trilobites that occurs about halfway during the Lower Cambrian , at the start of the stage called the Atdabanian . Olenellina are arguably the earliest trilobites in the fossil record as members of Redlichiina , although Ptychopariida and Eodiscina follow soon after. The suborder died out when the Lower Cambrian passed into the Middle Cambrian, at

54-468: A prothorax that generally has 14 or 15 segments, and an opisthothorax that has between 0 and up to 34 segments. In segment 3, the areas right and left of the axis (or pleural lobes) are often enlarged, sometimes carrying large trailing pleural spines. Segment 14 or 15 is often bearing a large spine at midline that points backwards. The pygidium is mostly very small with few segments, that are often difficult to discern. Unlike in other trilobite groups,

81-572: 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

108-401: 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

135-427: 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

162-659: 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 )

189-725: The Fallotaspidoidea are a paraphyletic group because it gave rise to the Redlichiina; he did not propose to restrict the Olenellina to the Olenelloidea, Judomioidea and Nevadioidea. Neither did he propose to assign this group of superfamilies to a newly formed order Olenellida, and consequently expand the Redlichiina to include the Fallotaspidoidea. This would imply that the Redlichiina would include taxa with and without dorsal sutures. The Olenellina appear suddenly at

216-696: 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

243-442: The Olenellina have an almost flat exoskeleton , that is only thinly calcified, and have crescent-shaped eye ridges. The suborder differs from all other trilobites by the lack of dorsal sutures in the head shield (or cephalon ). There is a ventral mouth plate (or conterminant hypostome ) with a very wide rostral plate extending between genal angles, with a perrostral suture (no connective sutures). The thorax may be composed of

270-483: 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

297-404: 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

SECTION 10

#1732776871830

324-402: 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

351-423: 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 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,

378-428: 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 the headshield (or cephalon ) very often carries

405-404: The early larval stage called protaspid is not known, and it is generally accepted that this is because the protaspid was not calcified. Redlichiida 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

432-683: The end of the stage called Toyonian . A feature uniting the Olenellina is the lack of rupture lines (or sutures ) in the headshield, which in other trilobites assist the periodic moulting (or ecdysis ), associated with arthropod growth. Some derived trilobites have lost facial sutures again (some Eodiscina , all Agnostina , and a few Phacopina ), but all of these are blind, while all Olenellina have eyes. The suborder contains four superfamilies: Olenelloidea (with 3 families and 5 stemgroup genera), Judomioidea (with 1 family and 3 stemgroup genera), Nevadioidea , and Fallotaspidoidea (with 3 families and 3 stemgroup genera). Lieberman, 2002, considered that

459-472: 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

486-910: 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

513-672: The first representatives to appear are Fallotaspididae, followed by Archaeaspididae, Nevadioidea and Holmiidae, and finally Biceratopsidae and Olenellidae. Significant deposits are found in Lantham Shale deposits within the Marble Mountains of southern California . The Olenellina are not known from South China, Australia and most of Latin America and Africa, where the first trilobites were Redlichiina , that had already developed dorsal sutures. As with most early trilobites,

540-575: 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

567-528: 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

SECTION 20

#1732776871830

594-428: 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

621-420: 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

648-583: The start of the Cambrian Series 2 (between Stage 2 Tommotian and Stage 3 Atdabanian ) approximately 521 million years ago, and disappear at the end of this Series (between Stage 4 Toyonian and Stage 5 Amgan ), 514 to 509 million years ago. The Olenellina probably first occurred on the paleocontinent Siberia and spread into the part of Gondwana that is now the Atlas Mountains , Baltica , Avalonia and Laurentia . In western Laurentia

675-578: 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

702-551: 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

729-561: 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,

#829170