Pseudoniscus is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods.

[7][6][1] 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.

[8] At least some species have a median spine in front of the carapace like the close-related Cyamocephalus.

[9] Within Pseudoniscus, P. roosevelti is one of the few synziphosurines that confirmed to have lateral compound eyes,[10] while the remain species lacking unambiguous evidence of it.