Pseudoniscus

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Pseudoniscus is an extinct genus of early chelicerate arthropods called synziphosurines. It lived during the Silurian period, and fossils have been found in the United Kingdom, the United States, and Estonia. It is part of the family Pseudoniscidae, along with Cyamocephalus.

The body’s front part (prosoma) was covered by a shield-like carapace with a curved rear edge and pointed spines at the sides. Many typical carapace features are not clearly visible in the fossils. Some species may have a median spine at the front, similar to Cyamocephalus.

Unlike many related fossil chelicerates, Pseudoniscus had an undivided abdomen with 10 segments (no clear separation into preabdomen and postabdomen).

Pseudoniscus roosevelti is one of the few species for which scientists are sure it had lateral compound eyes; for the other species, eyes have not been clearly documented.

Species in this genus include Pseudoniscus aculeatus (the type species), Pseudoniscus clarkei, Pseudoniscus falcatus, and Pseudoniscus roosevelti. The genus was once also named Neolimulus.