Harpetida

	Harpetida Harpetida is one of the eleven orders of the extinct arthropod class Trilobita. The first harpetid trilobites appear in the Upper Cambrian, and the last species die out at the end of the Devonian period. Harpetid trilobites are characterized among trilobites by bearing a comparatively large, semicircular brim around the cephalon (head) which is often perforated by small pores. This brim is thought to serve as a filter-feeding apparatus. The brim stretches backward on either side of the cephalon (head) and typically has a pronounced suture along the outside. The compound eyes are typically reduced to small tubercles, though they have strong ridges stretching to the glabella (central region of the cephalon). They also typically have 12 or more thoracic segments. The pygidia are usually small. The families of Harpetida were formerly included in the order Ptychopariida, but were recently given their own order (Ebach & McNamara 2002). The subclass Librostoma was erected in 1990 by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	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. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Entomaspididae Entomaspididae is a family of harpetid trilobites that ranges from the Upper Cambrian to Lower Ordovician of marine strata in China and the United States. Description Entomaspidids, as in other harpetid trilobites, have proportionally large, vaulted cephalons, shaped like croissants or bonnets, with the cheeks freed to be modified into long and curved spines in '' Entomaspis'' and '' Hypothetica''. Although the eyes of Entomaspididae are small compared to many other trilobites, the eyes are large when compared to other harpetids bearing eyes. Entomaspidids can be further distinguished from other harpetids by having a continuous border along the rim of the pygidium composed of small, stub-like spines.Suzuki, Yutaro. "Systematic position and palaeoecology of a cavity-dwelling trilobite, Ityophorus undulatus Warburg, 1925, from the Upper Ordovician Boda Limestone, Sweden." Paleontological research 6.1 (2002): 73-83. In overall appearance, the typical Entomaspidid is a near-circ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Hibbertia (trilobite) ''Hibbertia'' is a genus of trilobites. A new species, ''H. aodiensis'', was described from the late Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. T ... of China by Dong-Chan Lee in 2012. References Harpetida Ordovician trilobites of Asia {{harpetida-stub ... [...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]
	Entomaspis ''Entomaspis'' is an extinct genus of harpetid trilobite from Upper Cambrian to Early Ordovician marine strata of the United States. Species are typified by their proportionally large, vaulted, croissant-shaped or bonnet-shaped cephalons that have the cheeks freed to become elongated, curved librigenial spines, and by their comparatively large, crescent-shaped eyes (in comparison with other eyed harpetids). Species ''E. bridgei'' ''E. bridgei'' is a species found in marine strata of Missouri. ''E. clarki'' ''E. clarki'' is a species found in Lower Ordovician marine strata of Vermont Vermont () is a state in the northeast New England region of the United States. Vermont is bordered by the states of Massachusetts to the south, New Hampshire to the east, and New York to the west, and the Canadian province of Quebec to ....Shaw, Alan B. "Paleontology of Northwestern Vermont. XII. Fossils from the Ordovician Highgate Formation." Journal of Paleontology (1966): 1312-13 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Cephalon (arthropod Anatomy) The cephalon is the head section of an arthropod. It is a tagma, i.e., a specialized grouping of arthropod segments. The word cephalon derives from the Greek κεφαλή (kephalē), meaning "head". Insects In insects, ''head'' is a preferred term. The insect head consists of five segments, including three (the labial, maxillary and mandibular) necessary for food uptake, which are altogether known as the gnathocephalon and house the suboesophageal ganglion of the brain, as well as the antennal segment, and an ocular segment, as well as a non segmented fused section of the head where the archicerebrum is housed known as the acron. See also arthropod head problem. Chelicerates and crustaceans In chelicerates and crustaceans, the cephalothorax is derived from the fusion of the cephalon and the thorax, and is usually covered by a single unsegmented carapace. In relation with the arthropod head problem, phylogeny studies show that members of the Malacostraca class of crus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Bowmania (trilobite) ''Bowmania'' is the scientific name of two genera of organisms and may refer to: * ''Bowmania'' (plant), a genus of plants in the family Asteraceae, currently regarded as a synonym of ''Trixis'' * ''Bowmania'' (trilobite), a genus of trilobites in the order Harpetida {{Genus disambiguation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to the east, and the disputed territory of Western Sahara to the south. Mauritania lies to the south of Western Sahara. Morocco also claims the Spanish exclaves of Ceuta, Melilla and Peñón de Vélez de la Gomera, and several small Spanish-controlled islands off its coast. It spans an area of or , with a population of roughly 37 million. Its official and predominant religion is Islam, and the official languages are Arabic and Berber; the Moroccan dialect of Arabic and French are also widely spoken. Moroccan identity and culture is a mix of Arab, Berber, and European cultures. Its capital is Rabat, while its largest city is Casablanca. In a region inhabited since the Paleolithic Era over 300,000 years ago, the first M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]