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Proetida
Proetida is an order of trilobite that lived from the Ordovician to the Permian. It was the last order of trilobite to go extinct, finally dying out in the Permian-Triassic extinction event. Description These typically small trilobites resemble those of the order Ptychopariida, from which the new order Proetida was separated in 1975 by Fortey and Owens. Like the order Phacopida, the proetids have exoskeletons that sometime have pits or small tubercles, especially on the glabella (middle portion of the head). Because of their resemblance to the Ptychopariida in some features, the proetids are included in the subclass Librostoma. Unlike the trilobites of the phacopid suborder Phacopina, whose eyes are schizochroal, the proetids have the more common holochroal eyes. These eyes are characterized by close packing of biconvex lenses beneath a single corneal layer that covers all of the lenses. Each lens is generally hexagonal in outline and in direct contact with the others. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trilobite
Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period () and they flourished throughout the lower Paleozoic before slipping into a long decline, when, during the Devonian, all trilobite orders except the Proetida died out. The last extant trilobites finally disappeared in the mass extinction at the end of the Permian about 252 million years ago. Trilobites were among the most successful of all early animals, existing in oceans for almost 270 million years, with over 22,000 species having been described. By the time trilobites first appeared in the fossil record, they were already highly diversified and geographically dispersed. Because trilobites had wide diversity and an easily fossilized exoskeleton, they left an extensive fossil record. The stu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cummingella Belisama Dorsal Light2 CRF
''Cummingella'' is a genus of proetid trilobite in the family Phillipsiidae that lived from the earliest Carboniferous until the last species' extinction in the Middle Permian. Fossils have been found in corresponding marine strata of Western Europe, the United Kingdom and the United States. Distribution * ''C. arbizui'' was found in the Lower Carboniferous of Spain (Tournaisian, Perna Formation, 1.450 m SSE of Cerro de Perna, 5 km SE of Aliseda, Cáceres). * ''C. auge'', ''C. carringtonensis'', ''C. insulae'', and ''C. tuberculigenata'' occur at the Lower Carboniferous of the United Kingdom ( Asbian, Bee Low Limestones Formation, Treak Cliff, England). * ''C. auge'' was excavated from the earliest Carboniferous of the Czech Republic (Tournaisian, ''Scaliognathus anchoralis''-conodont zone, Brezina Formation, near Mokra village) and Germany (Tournaisian, Erdbach Limestone Formation, quarry at north-western margin of Steeden, Hessen; and quarry and slope at the Iberg-Winterb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ptychopariida
Ptychopariida is a large, heterogeneous order of trilobite containing some of the most primitive species known. The earliest species occurred in the second half of the Lower Cambrian, and the last species did not survive the Ordovician–Silurian extinction event. Trilobites have facial sutures that run along the margin of the glabella and/or fixigena to the shoulder point where the cephalon meets the thorax. These sutures outline the cranidium, or the main, central part of the head that does not include the librigena (free cheeks). The eyes are medial along the glabella on the suture line (and some species have no eyes). The fossils of the moults of trilobites can often be told from the fossils of the actual animals by whether the librigena are present. (The librigena, or cheek spines, detach during moulting.) In ptychopariids, short bladelike genal spines are often present on the tips of the librigena. The thorax is large and is typically made up of eight or more segments. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aulacopleura
''Aulacopleura'' is a genus of proetid trilobite that lived from the Middle Ordovician to the Middle Devonian. Some authors may classify this group as subgenus ''Otarion (Aulacopleura)''. The cephalon is semicircular or semielliptical, with border and preglabellar field. The glabella is short, with or without defined eye ridges connecting it with eyes of variable size. Spines at the rear outer corners of the cephalon (or genal spines) are present, typically reaching back to the 2nd to 4th thorax segment. The 'palate' (or hypostome) is not connected to the dorsal shield of the cephalon (or natant). The cephalon is pitted, or has small tubercles. The thorax has up to 22 segments. The pleural ends are usually rounded. The pygidium is small (micropygous), with an even margin. ''A. koninckii'' had a modern type of compound eye. Taxonomy Barrande described ''Arethusa koninckii'' in 1846. However, ''Arethusa'' was occupied since it was used by De Montfort in 1808 for a foram protist. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permian
The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleozoic Era; the following Triassic Period belongs to the Mesozoic Era. The concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the region of Perm in Russia. The Permian witnessed the diversification of the two groups of amniotes, the synapsids and the sauropsids ( reptiles). The world at the time was dominated by the supercontinent Pangaea, which had formed due to the collision of Euramerica and Gondwana during the Carboniferous. Pangaea was surrounded by the superocean Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior. Amniotes, which could better cope with these drier conditions, rose to dominance in place of their am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyphaspis
''Cyphaspis'' is a genus of small trilobite that lived from the Late Ordovician to the Late Devonian. Fossils have been found in marine strata in what is now Europe, Africa and North America. Various species had a compact body, and a large, bulbous glabellum. Many species had long spines arranged similarly to closely related genera, such as '' Otarian'', '' Otarionella'', '' Chamaeleoaspis'', and '' Namuropyge''. Species The following species in the genus ''Cyphaspis'' have been described: *''C. anticostiensis'' *''C. bellula'' *''C. bluhmi'' Van Viersen & Holland, 2016 *''C. boninoi'' Van Viersen & Holland, 2016 *''C. bowingensis'' *''C. buchbergeri'' Adrain & Chatterton, 1996 *''C. burmeisteri'' *''C. ceratophthalma'' Goldfuss, 1843 ( type) *''C. ceratophthalmoides'' *''C. clintoni'' *''C. coelebs'' *''C. convexa'' *''C. craspedota'' *''C. dereimsi'' *''C. diadema'' *''C. eximia'' Van Viersen & Holland, 2016 *''C. foumzguidensis'' Van Viersen & Holland, 2016 *'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phacopida
Phacopida ("lens-face") is an order of trilobites that lived from the Late Cambrian to the Late Devonian. It is made up of a morphologically diverse assemblage of taxa in three related suborders. Characteristics Phacopida had 8 to 19 thoracic segments and are distinguishable by the expanded glabella, short or absent preglabellar area, and schizochroal (Phacopina) or holochroal (Cheirurina and Calymenina) eyes. Schizochroal eyes are compound eyes with up to around 700 separate lenses. Each lens has an individual cornea which extended into a rather large sclera. The development of schizochroal eyes in phacopid trilobites is an example of post-displacement paedomorphosis. The eyes of immature holochroal Cambrian trilobites were basically miniature schizochroal eyes. In Phacopida, these were retained, via delayed growth of these immature structures (post-displacement), into the adult form. '' Eldredgeops rana'' (Phacopidae) and '' Dalmanites limulurus'' (Dalmanitidae) are tw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chamaeleoaspis
''Chamaeleoaspis'' is a genus of tiny trilobites found in Early to Middle Eifelian marine strata of Africa and Europe. The two species look very similar to the trilobites of the related genera ''Cyphaspis'' and '' Otarionella'', in which the species were originally, successively classified in. Fossils of the older species, ''C. lkomalii'', are found in a locality at the southern end of the Maider Basin, in the Anti-Atlas Mountains. Fossils of the type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ..., ''C. chamaeleo'', are found in the Middle Eifelian-aged Ohle Formation in Endorf, Germany.. References External links Proetida genera Devonian trilobites of Africa Devonian trilobites of Europe Early Devonian first appearances Trilobites of Africa Middle Devoni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sister Group
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and taxon B are sister groups to each other. Taxa A and B, together with any other extant or extinct descendants of their most recent common ancestor (MRCA), form a monophyletic group, the clade AB. Clade AB and taxon C are also sister groups. Taxa A, B, and C, together with all other descendants of their MRCA form the clade ABC. The whole clade ABC is itself a subtree of a larger tree which offers yet more sister group relationships, both among the leaves and among larger, more deeply rooted clades. The tree structure shown connects through its root to the rest of the universal tree of life. In cladistic standards, taxa A, B, and C may represent specimens, species, genera, or any other taxonomic units. If A and B are at the same taxonomic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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