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Artiopoda
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 The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ... 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 elong ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cheloniellid
Cheloniellida is a taxon (usually referred to as an order) of extinct Paleozoic arthropods. As of 2018,Wendruff, Andrew James, et al. "New cheloniellid arthropod with large raptorial appendages from the Silurian of Wisconsin, USA." BioRxiv (2018): 407379/ref> 7 monotypic genera of cheloniellids had been formally described, whose fossils are found in marine strata ranging from Ordovician to Devonian in age. Cheloniellida has a controversial phylogenetic position, with previous studies associated it as either a member or relative of various fossil and extant arthropod taxa. It was later accepted as a member of Vicissicaudata within Artiopoda. Morphology The flattened, ovoid body of cheloniellid comprises an eye-bearing cephalon (head) and segmented trunk region, dorsally divided by a series of tergites (dorsal exoskeleton). The cephalon could be divided into procephalon and gnathocephalon. Compared to other members of Artiopoda, the head shield (dorsal exoskeleton of cephalon) of ... [...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] |
Retifacies
''Retifacies abnormalis'' is an extinct arthropod that lived in the lower Cambrian (about 518 million years ago). Its fossil remains have been found in the Maotianshan Shales of Yunnan, China. It is a member of the Artiopoda, and closely related to ''Pygmaclypeatus''. Description ''Retifacies'' was relatively large sized, reaching a carapace length of , and a total length of , including the extended Antenna (zoology), antennae and tailspine. The head shield was broad and short, and appears to have lacked eyes. The antennae had 17 segments, which telescoped into each other, with spines present on the underside of the antennae at the boundary between the segments. Also present on the head were four closely spaced pairs of appendages, the first three of which were uniramous (single branched), while the last was biramous (two branched). The three uniramous appendages had six segments (podomeres), each ending with a terminal claw, with the endopod (lower leg-like branch) of the fou ... [...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] |
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] |
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] |
Vicissicaudata
Vicissicaudata is an unranked group of artiopodan arthropods, containing Cheloniellida, Aglaspidida and several other genera outside these groups like ''Sidneyia'' and ''Emeraldella.'' Description Vicissicaudatans are similar to most other artiopods in shape, with rounded bodies consisting of many wide tergites, sometimes with a distinguishable axis along the midline. This clade is defined by a differentiated posterior region, often ending in a telson and caudal appendages. The morphology of this posterior region varies between clades. Aglaspidids, alongside '' Eozetetes'' and '' Carimersa'', have long styliform telsons and relatively small, flap-like caudal appendages while cheloniellids and '' Tardisia'' have much longer caudal appendages similar to the caudal furcae of various taxa, alongside much smaller telsons more resembling the postabdominal segments. The paraphyletic "xenopods" are more similar to those of aglaspidids, also with long telsons and flap-like caudal app ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Emeraldella
''Emeraldella'' is a genus of arthropod known from the Middle Cambrian of North America. The type species ''E. brocki'' was described in 1912 from the Burgess Shale. 21 specimens of ''Emeraldella'' are known from the Greater Phyllopod bed, where they comprise < 0.1% of the community. A re-study on the species was done in 2012. A second species ''E. brutoni'' is known from the Wheeler Shale, which was described in 2011. An additional specimen of ''E. brutoni'' was described in 2019, which revealed more of the anatomy. It has been placed as a basal member of the clade Vicissicaudata within Artiopoda, a group of arthropods containing trilobites and their relatives. Description [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cheloniellon
''Cheloniellon'' is a monotypic genus of cheloniellid arthropod, known only by one species, ''Cheloniellon calmani'', discovered from the Lower Devonian Hunsrück Slate of Germany. Morphology ''Cheloniellon'' range about 20 centimeters in body length (excluding appendages). The flattened, ovoid body compose of 11 tergites (dorsal exoskeleton), all but the posteriormost are laterally expanded and covered the appendages underneath each of them. The boundaries between tergites have a radiated appearance. Dorsal surface of the first tergite have a pair of kidney-shaped eyes. Based on the differentiation of corresponding appendages, the first 2 tergites and the remaining 9 tergites were interpreted as those of cephalon (head) and trunk, respectively. Contray to the widely-referred reconstruction by Stürmer & Bergström (1978), but as most of the Cheloniellids, There is no evidence of telson (a medial tail-like terminal structure) in any described fossil materials.Wendruff, Andrew ... [...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] |
Bailongia
''Bailongia'' is an extinct genus of arthropod known from a single species ''Bailongia longicaudata'' (''longicaudata'' from Latin: "long-tailed") found in the Cambrian Stage 4 aged Maotianshan Shales, Guanshan Biota of Yunnan, China. It was around 5mm long and had a large head shield, nine overlapping tapering tergites and a relatively elongate tailspine. It has been recovered in a relatively Basal (phylogenetics), basal position within Artiopoda, more derived than ''Squamacula'' or Protosutura, but outside Trilobitomorpha or Vicissicaudata. Phylogeny After Jiao et al. 2021. References Artiopoda Cambrian arthropods of Asia Cambrian China Paleontology in Yunnan Fossil taxa described in 2021 Cambrian genus extinctions {{Paleo-arthropod-stub ... [...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] |
