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Synziphosurina
Synziphosurina is a paraphyletic group of chelicerate arthropods previously thought to be basal horseshoe crabs (Xiphosura). It was later identified as a grade composed of various basal euchelicerates, eventually excluded form the monophyletic Xiphosura ''sensu stricto'' and only regarded as horseshoe crabs under a broader sense ('Xiphosura' ''sensu lato''). Synziphosurines survived at least since early Ordovician to early Carboniferous in ages, with most species are known from the in-between Silurian strata. File:20200920 Synziphosurina dorsal segmentation.png, Dorsal morphology and variation of opisthosomal segmentation across synziphosurines. While ''Weinbergina'' and ''Willwerathia'' being exceptionally large, most synziphosurines are small arthropods with body length ranging only about a few centimeters long. The body of synziphosurine composed of a prosoma covered by a dome-like carapace (prosomal dorsal shield) and an opisthosoma with usually unfused 9-11 segments expre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Venustulus
''Venustulus'' is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. ''Venustulus'' was regarded as part of the clade Prosomapoda. Fossils of the single and type species, ''V. waukeshaensis'', have been discovered in deposits of the Silurian period in Wisconsin, in the United States. ''Venustulus'' is one of the few synziphosurine genera with fossil showing evidence of appendages, the other ones being '' Weinbergina, Anderella'' and ''Camanchia''. Despite often being aligned close to Horseshoe crabs, it has been found that ''Venustulus'' and its relatives form a group made up of various basal euchelicerate arthropods more distant to the xiphosurans. Description ''Venustulus'' is the third largest member of its grouping just behind ''Willwerathia'' and ''Weinbergina'' respectively. This arthropod appears to be blind due to the lack of eyes on its carapace, suggesting it lived either in deep water or buried in the sediments. Unlike modern horseshoe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bunaia
''Bunaia'' is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. ''Bunaia'' was tentatively placed as part of the clade Planaterga. The genus contains at least one species: ''Bunaia woodwardi'' from the Silurian period in Svalbard, Norway. Only a few morphological information of ''B''. ''woodwardi'' had been confirmed, as the species known only from poorly preserved specimens compose of semicircular carapace, fragments of opisthosoma and disarticulated telson. The placement of ''"Bunaia" heintzi'' (known only by a single carapace from the Silurian period in the United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...) within this genus had been questioned and required further investigation. References Synziphosurina Silurian first appea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Willwerathia
''Willwerathia'' is a genus of synziphosurine, a paraphyletic group of horseshoe crab-like fossil chelicerate arthropods. ''Willwerathia'' known only by one species, ''Willwerathia laticeps'', discovered in deposits of the Devonian period from the Klerf Formation, in the Rhenish Slate Mountains of Germany. Morphology As a synziphosurine, ''Willwerathia'' is unusually large and so far the largest known synziphosurine, with largest carapace measured about 90mm in width. Prosoma of ''Willwerathia'' covered by a vaulted carapace with pointed genal spines, recurved (M-shaped) ophthalmic ridges and pairs of dorsal nodes. Tergites of the opisthosoma are either incomplete or disarticulated in available fossil materials, making it difficult to reveal the original number of opisthosomal segments. The opisthosoma of ''Willwerathia'' most likely compose of 10 segments, each expressed by a tergite that bore a median dorsal spine and a pair of tergopleurae (lateral extensions). The opisth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bunodes
''Bunodes'' is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. ''Bunodes'' was regarded as part of the clade Planaterga. Fossils of the single and type species, ''B. lunula'', have been discovered in deposits of the Silurian period in Ludlow, England (in the United Kingdom). ''Bunodes'' is the type genus of the family Bunodidae, the other genera of the same family being '' Limuloides''. ''Bunodes'' is characterized by a vaulted carapace with radiated hump-like ridges. Within the 10-segmented opisthosoma, the first opisthosomal tergite A ''tergum'' (Latin for "the back"; plural ''terga'', associated adjective tergal) is the dorsal ('upper') portion of an arthropod segment other than the head. The anterior edge is called the 'base' and posterior edge is called the 'apex' or 'mar ... is greatly reduced and always covered by the posterior region of preceding carapace, while the second tergite is significantly well-developed. the last 3 opisthosomal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudoniscus
''Pseudoniscus'' is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. ''Pseudoniscus'' was regarded as part of the clade Planaterga. Fossils of the genus have been discovered in Deposition (geology), deposits of the Silurian Period (geology), period in the United Kingdom, the United States and Estonia. ''Pseudoniscus'' is one of the two members of the Family (biology), family Pseudoniscidae, the other being ''Cyamocephalus''. The prosoma of ''Pseudoniscus'' covered by a carapace with recurved posterior margin and pointed genal spines. Most of the dorsal feature on the carapace (e.g. ophthalmic ridges, cardiac lobe) are not significantly expressed. At least some species have a median spine in front of the carapace like the close-related ''Cyamocephalus''. Unlike most other synziphosurines with opisthosoma subdivided into a wide preabdomen and narrow postabdomen, the 10-segmented opisthosoma of ''Pseudoniscus'' possess undivided, metameric segmentatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Legrandella
''Legrandella'' is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. ''Legrandella'' was regarded as part of the clade Prosomapoda. Fossils of the single and type species, ''L. lombardii'', have been discovered in deposits of the Devonian period in Cochabamba, Bolivia. The prosoma of ''Legrandella'' covered by a vaulted carapace with anterior projection, blunt genal cornua (posterolateral corners), humped cardiac lobe and pairs of radiated grooves. Alongside ''Pseudoniscus roosevelti'', ''Legrandella lombardii'' is one of the few synziphosurine species that confirmed to have lateral compound eyes. The eyes are slit-like, located just below the ophthalmic ridges on each side of the carapace. The opisthosoma is externally 11-segmented, subdivided into a 8-segmented preabdomen and 3-segmented postabdomen. Tergite of the 1st preabdomimal segment is a reduced microtergite while the remaining 7 tergite possess axial nodes and spine-like tergopleurae (lat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Limuloides
''Limuloides'' is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. ''Limuloides'' was regarded as part of the clade Planaterga. Fossils of the genus have been discovered in deposits of the Silurian period in the United Kingdom and potentially in the United States. ''Limuloides'' is one of the two genera of the family Bunodidae, the other being the type genus ''Bunodes''. ''Limuloides'' is characterized by a carapace with radiated ridges and serrated lateral regions, and an opisthosoma with rows of nodes. ''Limuloides'' was once though to have lateral compound eye A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which disti ...s on its carapace, but later investigation did not find any evidence of it. References Synziphosurina Planaterga Silurian first appe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anderella
''Anderella'' is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. ''Anderella'' was regarded as part of the clade Prosomapoda. Fossils of the single and type species, ''A. parva'', have been discovered in deposits of the Carboniferous period in Montana, in the United States. ''Anderella'' is the first and so far (as of 2020) the only Carboniferous synziphosurine being described, making it the youngest member of synziphosurines. ''Anderella'' is also one of the few synziphosurine genera with fossil showing evidence of appendages, but the details are obscure due to their poor preservation. The prosoma of ''Anderella'' possess a suboval carapace slightly longer than the externally 10-segmented opisthosoma (excluding telson). A row of axial nodes run through the opisthosomal tergite A ''tergum'' (Latin for "the back"; plural ''terga'', associated adjective tergal) is the dorsal ('upper') portion of an arthropod segment other than the head. The ante ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Camanchia
''Camanchia'' is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. ''Camanchia'' was regarded as part of the clade Prosomapoda. Fossils of the single and type species, ''C. grovensis'', have been discovered in deposits of the Silurian period in Iowa, in the United States. Alongside '' Venustulus'', ''Camanchia'' is one of the only Silurian synziphosurine with fossil showing evidence of appendages. The prosoma of ''Camanchia'' covered by a smoothly curved subtriangular carapace with broad doublure (ventral thickening run through the margin of carapace). Detail of the 6 prosomal appendage pairs (chelicerae+5 leg pairs) obscure, at least the first leg pair (appendage II) have spur-like terminations. Opisthosoma is externally 10-segmented with tergites possses blunt pleurae (lateral extension). The last 3 opisthosomal segments forming a narrow postabdomen with short pleurae. Telson The telson () is the posterior-most division of the body of an art ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pasternakevia
''Pasternakevia'' is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. ''Pasternakevia'' was regarded as part of the clade Planaterga. Fossils of the single and type species, ''P. podolica'', have been discovered in deposits of the Silurian period in Podolia, Ukraine. The prosoma of ''Pasternakevia'' covered by a smooth, semicircular carapace with rounded genal cornua (posterolateral corner of carapace). Within the 10-segmented opisthosoma, tergite of the first segment is reduced and usually hidden under the preceding carapace, while the second one is significantly arched and well-developed. All but the first tergite possess well-developed pleurae (lateral extension). A complete telson The telson () is the posterior-most division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment of the arthropod body, or an additional division that is not a true segment on accou ... is yet to be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weinbergina Opitzi
''Weinbergina'' is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Fossils of the single and type species, ''W. opitzi'', have been discovered in deposits of the Devonian period in the Hunsrück Slate, Germany. Morphology ''Weinbergina'' is a relatively large synziphosurine, ranging about 7 cm to 10 cm in full body length. The prosoma is covered by a semicircular carapace with blunt genal cornua (posterolateral corners). There is possible evidence of lateral eyes located just below the ophthalmic ridges. The opisthosoma is externally 10-segmented, expressed by tergites that possess blunt tergopleurae (lateral extension) and axial nodes. However, the opisthosoma is most likely 11-segmented in origin, with the first segment being highly reduced (a synapomorphy of euchelicerates) and possibly covered by the preceding carapace. The last 3 segments form a narrow postabdomen and lacking lateral nodes. Compared to other synziphosurines with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weinbergina
''Weinbergina'' is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Fossils of the single and type species, ''W. opitzi'', have been discovered in deposits of the Devonian period in the Hunsrück Slate, Germany. Morphology ''Weinbergina'' is a relatively large synziphosurine, ranging about 7 cm to 10 cm in full body length. The prosoma is covered by a semicircular carapace with blunt genal cornua (posterolateral corners). There is possible evidence of lateral eyes located just below the ophthalmic ridges. The opisthosoma is externally 10-segmented, expressed by tergites that possess blunt tergopleurae (lateral extension) and axial nodes. However, the opisthosoma is most likely 11-segmented in origin, with the first segment being highly reduced (a synapomorphy of euchelicerates) and possibly covered by the preceding carapace. The last 3 segments form a narrow postabdomen and lacking lateral nodes. Compared to other synziphosurines wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
_from_the_Waukesha_lagerstätte.jpg "Click for more on -> Venustulus")
