Synziphosurina Temporal range:
| |
---|---|
Venustulus waukeshaensis (top left), Cyamocephalus loganensis (top right), Weinbergina opitzi (center), Limuloides limuloides (bottom left), and Legrandella lombardii (bottom right). | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Subphylum: | Chelicerata |
Clade: | Prosomapoda |
Suborder: | †
Synziphosurina Packard 1886 |
Genera [1] [2] [3] | |
Synziphosurina is a paraphyletic group of chelicerate arthropods previously thought to be basal horseshoe crabs ( Xiphosura). [4] It was later identified as a grade composed of various basal euchelicerates, [4] [5] [6] [3] [2] eventually excluded form the monophyletic Xiphosura sensu stricto [4] and only regarded as horseshoe crabs under a broader sense ('Xiphosura' sensu lato). [3] [5] Synziphosurines survived at least since early Ordovician to early Carboniferous in ages, with most species are known from the in-between Silurian strata. [2]
While Weinbergina and Willwerathia being exceptionally large, [7] most synziphosurines are small arthropods with body length ranging only about a few centimeters long. [8]
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 expressed by tergites. [2] With the exception of Pseudoniscus [8] and Pasternakevia, [9] the last 3 opisthosomal segments precede the spine-like telson are specialized into a narrow postabdomen (pretelson), [2] while the remaining wider segments referred to as preabdomen. [8] A reduced anteriormost tergite (microtergite) originated from the first opisthosomal segment is observable at least in some genera. [8] [4] Most synziphosurines are possibly blind, with only a few species showing possible (e.g. Weinbergina opitzi) or clear (e.g. Legrandella lombardii) evidences of lateral compound eyes on their carapaces. [10] [2] Evidences of appendages are scarce, fragmentary known from Anderella parva, [11] Camanchia grovensis [12] and Venustulus waukeshaensis [13] while exceptionally well-documented in Weinbergina opitzi. [14] [2] The prosoma possess a pair of chelicerae and at least 5 pairs of walking legs while the opisthosoma probably has 6 pairs of plate-like opercula. [4] [15]
As of 2020, at least 13 genera and 20 species were considered to be synziphosurines. [2] The even basal euchelicerates Offacolus and Dibasterium, the questionable genus Borchgrevinkium, as well as the Dekatriata-related Houia and Winneshiekia, may also regarded as members of synziphosurines in some literatures. [16] [5] [6] [17] [2]
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Synziphosurina Temporal range:
| |
---|---|
Venustulus waukeshaensis (top left), Cyamocephalus loganensis (top right), Weinbergina opitzi (center), Limuloides limuloides (bottom left), and Legrandella lombardii (bottom right). | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Subphylum: | Chelicerata |
Clade: | Prosomapoda |
Suborder: | †
Synziphosurina Packard 1886 |
Genera [1] [2] [3] | |
Synziphosurina is a paraphyletic group of chelicerate arthropods previously thought to be basal horseshoe crabs ( Xiphosura). [4] It was later identified as a grade composed of various basal euchelicerates, [4] [5] [6] [3] [2] eventually excluded form the monophyletic Xiphosura sensu stricto [4] and only regarded as horseshoe crabs under a broader sense ('Xiphosura' sensu lato). [3] [5] Synziphosurines survived at least since early Ordovician to early Carboniferous in ages, with most species are known from the in-between Silurian strata. [2]
While Weinbergina and Willwerathia being exceptionally large, [7] most synziphosurines are small arthropods with body length ranging only about a few centimeters long. [8]
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 expressed by tergites. [2] With the exception of Pseudoniscus [8] and Pasternakevia, [9] the last 3 opisthosomal segments precede the spine-like telson are specialized into a narrow postabdomen (pretelson), [2] while the remaining wider segments referred to as preabdomen. [8] A reduced anteriormost tergite (microtergite) originated from the first opisthosomal segment is observable at least in some genera. [8] [4] Most synziphosurines are possibly blind, with only a few species showing possible (e.g. Weinbergina opitzi) or clear (e.g. Legrandella lombardii) evidences of lateral compound eyes on their carapaces. [10] [2] Evidences of appendages are scarce, fragmentary known from Anderella parva, [11] Camanchia grovensis [12] and Venustulus waukeshaensis [13] while exceptionally well-documented in Weinbergina opitzi. [14] [2] The prosoma possess a pair of chelicerae and at least 5 pairs of walking legs while the opisthosoma probably has 6 pairs of plate-like opercula. [4] [15]
As of 2020, at least 13 genera and 20 species were considered to be synziphosurines. [2] The even basal euchelicerates Offacolus and Dibasterium, the questionable genus Borchgrevinkium, as well as the Dekatriata-related Houia and Winneshiekia, may also regarded as members of synziphosurines in some literatures. [16] [5] [6] [17] [2]
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