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 deposits of the Silurian period in the United Kingdom, the United States and Estonia. "Pseudoniscus" is one of the two members of the 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 carapce (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 segmentation similar to "Pasternakevia". Within "Pseudoniscus", "P". "roosevelti" is one of the few synziphosurines that confirmed to have lateral compound eyes, while the remain species lacking unambiguous evidence of it.