|
Artiopodan
Artiopoda is a clade of extinct arthropods that includes trilobites and their close relatives. It was erected by Hou and Bergström in 1997 to encompass a wide diversity of arthropods that would traditionally have been assigned to the Trilobitomorpha. Trilobites, in part due to abundance of findings owing to their mineralized exoskeletons, are by far the best recorded, diverse, and long lived members of the clade. Other members, which lack mineralised exoskeletons, are known mostly from Cambrian deposits. Description According to Stein and Selden (2012) artiopods are recognised by the possession of filiform antennulae, limbs with bilobate exopods (upper branches), with the proximal (closest to base of the limb) lobe being elongate and bearing a lamella, while the distal (further from the limb base) lobe is paddle-shaped and setiforous (bearing hair-or bristle like structures). The limb endopod (inner, leg-like branch) has seven podomeres/segments, with first four podomeres be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Squamacula
''Squamacula'' is an extinct artiopodan arthropod from the Cambrian Series 2. The type species ''S. clypeata'' was described in 1997 from the Chengjiang biota of Yunnan, China. At the time of description there were only two known specimens of ''S. clypeata'', but now there are at least six known specimens. In 2012 a second species ''S. buckorum'' was described from the Emu Bay Shale of Australia. Etymology The genus ''Squamacula'' is derived from the Latin word ''squama'', meaning scale, and the diminutive suffix -''culus'', indicating that the animal is relatively small. The species ''clypeata'' is derived from the Latin word ''clypeatus'', meaning shield-shaped. It was named this in reference to its shield-like outline. Description ''Squamacula clypeata'' is flattened (dorsoventrally). It has 11 segments in total: the cephalon (the head), nine thoracic tergites (each of which covers a somite), and one pygidium. It has a doublure, a piece of exoskeleton that covers part of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sidneyia
''Sidneyia'' is an extinct marine arthropod known from fossils found from the Early to the Mid Cambrian of China and the Mid Cambrian Burgess Shale of British Columbia, Canada. Description Sidneyia size comparison.svg, Size comparison of ''Sidneyia'' species Rsos211134f08 d.jpg, Biramous limb of ''Sidneyia inexpectans'' ''Sidneyia inexpectans'' reached lengths of at least . The largest known specimen of ''S. minor'' is around long and wide, while the largest specimen of ''S. malongensis'' is long and wide. The head shield is short, with notches present on the sides to accommodate stalked eyes, with the underside having a Hypostome (trilobite), hypostome. The head has a pair of segmented antennae, as well as three pairs of post-antenal appendages. This was followed by a thorax, which had eight to ten segments/Tergum, tergites, each associated with a pair of biramous (two branched) appendages, this was followed with one to three abdomen segments/tergites, with the body termi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thulaspis
''Thulaspis'' is an extinct genus of artiopodan arthropod from the Cambrian Stage 3 aged Sirius Passet site in Greenland. It is thought to be a close relative of '' Squamacula'', and is possibly one of the most basal members of Artiopoda. Description ''Thulaspsis'' was relatively large-sized. The largest specimen is about wide and long. The carapace is overall oval-shaped was convex and likely stiff in life, with a raised central axis. The head is broad and bears a pair of antennae, which have at least 20 rectangular segments, and likely two pairs of biramous (two branched) limbs.The body has 15 thoracic segments, which curve forwards in the first few segments, before becoming straight in the fourth and fifth segments, then increasingly posteriorly curved in subsequent segments. At least the first 11 thoracic segments are associated with pairs of biramous limbs. The biramous limbs have robust endopods (lower, leg-like branches), and flap-shaped exopods (upper branches). The b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trilobita
Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most successful of all early animals, existing in oceans for almost 270million years, with over 22,000 species having been described. Because trilobites had wide diversity and an easily fossilized mineralised exoskeleton made of calcite, they left an extensive fossil record. The study of their fossils has facilitated important contributions to biostratigraphy, paleontology, evolution, evolutionary biology, and plate tectonics. Trilobites are placed within the clade Artiopoda, which includes many organisms that are morphologically similar to trilobites, but are largely unmineralised. The relationship of Artiopoda to other arthropods is uncertain. Trilobites evolved into many ecological niches; some moved over the seabed as predators, scavengers, or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xandarellida
Xandarellida is an extinct order of artiopod arthropods known exclusively from the Middle Cambrian of China and Siberia. Morphology In terms of anatomy, xandarellids share numerous characteristics such as a natant hypostome, alongside a unique feature known as “segment decoupling” where the amount of limbs exceeds the amount of tergites. They also share a posteriorly extended semicircular head shield and ventral stalked eyes. The genus '' Cindarella'' in particular has complex eyes, with over 2000 ommatidia in each. ''Cindarella'' also has a large anterior spine on the fifteenth tergite. '' Xandarella'' has an unusual tripartite head shield, with ventral eye slits likely retained from the ancestral stalked eyes, alongside possibly lacking the anterior spine. '' Phytophilaspis'' has an especially intricate head shield, sharing its tripartite nature with ''Xandarella'' alongside bearing several sutures all over its body and seemingly having almost completely fused tergites. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Agnostida
Agnostida are an order of extinct arthropods which have classically been seen as a group of highly modified trilobites, though some recent research has doubted this placement. Regardless, they appear to be close relatives as part of the Artiopoda. They are present in the Lower Cambrian fossil record along with trilobites from the Redlichiida, Corynexochida, and Ptychopariida orders, and were highly diverse throughout the Cambrian. Agnostidan diversity severely declined during the Cambrian-Ordovician transition, and the last agnostidans went extinct in the Late Ordovician. Systematics The Agnostida are divided into two suborders — Agnostina and Eodiscina — which are then subdivided into a number of families. As a group, agnostids are isopygous, meaning their pygidium is similar in size and shape to their cephalon. Most agnostid species were eyeless. The systematic position of the order Agnostida within the class Trilobita remains uncertain, and there has been c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zhiwenia
''Zhiwenia'' is a genus of artiopods that existed during Stage 3 of the Cambrian period and was uncovered in the Xiaoshiba Lagerstätte in China. Only one species is known, ''Zhiwenia coronata''. It is the sister taxon of '' Australimicola'' in the newly defined clade Protosutura, which is itself the sister group of Trilobitomorpha Artiopoda is a clade of extinct arthropods that includes trilobites and their close relatives. It was erected by Hou and Bergström in 1997 to encompass a wide diversity of arthropods that would traditionally have been assigned to the Trilobitomor .... References Cambrian arthropods of Asia Artiopoda {{Paleo-arthropod-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nektaspid
Nektaspida (also called Naraoiida, Nektaspia and Nectaspida) is an extinct order of non- mineralised artiopodan arthropods. They are known from the lower-Cambrian to the upper Silurian. Originally classified as trilobites, which they superficially resemble, they are now placed as close relatives as members of the Trilobitomorpha within Artiopoda. The order is divided into three major families; Emucarididae, Liwiidae, and Naraoiidae. Naming history and taxonomic placement The order was originally proposed by Raymond in 1920 as Nektaspia. Størmer corrected it to Nectaspida for the 1959 ''Treatise on Invertebrate Paleontology'' to conform with the names of the other trilobite orders. Whittington described it in 1985 with the spelling Nektaspida; the revised 1997 Treatise by Raymond and Fortey uses this spelling, as do other modern works. Whittington (1985) placed the order in the Trilobita. Cotton & Braddy (2000) place it in a new "Trilobite clade" containing the Trilobita, r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Falcatamacaris
''Falcatamacaris'' is an extinct genus of Cambrian artiopodan arthropod, only known from the type species ''F. bellua'' described in 2014, from the Guzhangian (Cambrian Stage 3) aged Weeks Formation in Utah Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea .... The holotype specimen is over 10 cm long (not including the absent telson). The trunk consists of 11 tergites, with crescent shaped pleural spines. Its placement within the Artiopoda was unresolved. References Artiopoda {{Paleo-arthropod-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Australimicola
''Australimicola'' is a monotypic genus of ancient aquatic arthropods that are related to trilobites, they lived in the Cambrian period alongside them 538.8 million to 485.4 million years ago. Only a single species has been described in this genus, ''Australimicola spriggi''. It was discovered in the Emu Bay Shale on Kangaroo Island, south Australia. This fossil species is closely related to the Conciliterga clade, which includes genera like ''Helmetia'', '' Kuamaia'' and '' Rhombicalvaria.'' It is characterized by an elongated trunk with 23 thoracic tergites, spatulate pleural tips and a small pygidium The pygidium (: pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is compos ... with a pair of elongated pleural spines. References Artiopoda Fossil taxa described in 2012 Prehistoric arthropod ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conciliterga
Conciliterga is an extinct order of artiopod arthropods, exclusively known from the Middle Cambrian. They are placed within the clade Trilobitomorpha, which contains the trilobites and their closest relatives. Conciliterga is united by their partially or wholly fused tergites, which gives rise to their name (Conciliterga is composed of the Latin words ''concilio'' ("to unite") and ''tergum'' ("back")). Most members of this clade are elliptical in body shape, with 6-9 thoracic tergites, a head shield and a large tail shield in the members with incomplete tergite fusion. These members, which formerly comprised the order Helmetiida (which currently only contains ''Helmetia'', '' Rhombicalvaria'' and '' Kuamaia''), also have various other characteristics like a lack of axial region, rostral and pararostral plates on the head, and compound eyes near the rostral plate. In addition, they have essentially uniform biramous limbs running down the body with coarse endopods, alongside a pair ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acanthomeridion
''Acanthomeridion'' is an extinct arthropod found in the Cambrian Stage 3 aged Chengjiang biota deposits of Yunnan, China. It is a member of Artiopoda, placing it as a close relative of trilobites. Morphology Specimens of ''Acanthomeridion'' range in length from measured along the midline (sagittal plane). The exoskeleton was unmineralised. The head shield was roughly triangular in shape, rounded towards the front. A pair of compound eyes were accommodated by notches at the posterior edge of the head shield. Over the course of growth, the head became proportionally wider relative to body length. On the underside of the head, a pair of teardrop-shaped plates attached to the head shield, with their outer posterior edges forming a pair of spines projecting backwards from the head. The mouth region had an axe-shaped hypostome. The head bore four pairs of appendages, including a pair of antennae with at least 43 segments, with these segments becoming narrower and shorter towards t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
