Furca (genus)

Furca (Latin for "fork") is an extinct genus of marrellomorph arthropod known from the Sandbian stage (upper Ordovician period) of the Czech Republic. At least three distinct species have been described although they may all be synonyms of the type species, "Furca bohemica". A tentative additional species, "Furca mauretanica": was proposed for specimens discovered in Morocco, but this species remains a "nomen nudum" until formally published.
Description.
"Furca" is characterized by a broad head shield with three pairs of prominent spines: front (anterolateral), side (mediolateral) and rear (posterolateral). The head shield of "Furca" ranged from long and at maximum width. The mediolateral spines are long and strongly curved. The outline of the head shield possess a fringe of small, gently curving secondary spines, between long. Appendages are unknown from fossils.
Paleobiology.
"Furca" fossils have been found in sediments indicative of shallow marine habitats. Since appendages and other body parts are unknown, no firm conclusions can be made of the biology of "Furca". However, comparisons to other marrellomorphs and living arthropods such as horseshoe crabs suggest a benthic marine lifestyle: dwelling on the sea floor.
Classification.
"Furca" is assigned to the marrellomorph family Mimetasteridae, which also includes "Mimetaster" of the Lower Devonian. Other, more distantly related marrellomorphs include the well-known "Marrella" of the Burgess Shale as well the less-common "Vachonisia" and "Xylokorys".
Taxonomic history.
With its unusual anatomy, "Furca" has a colorful taxonomic history. The first specimens were discovered by Joachim Barrande, who named them "Furca bohemica" (Latin for "Bohemian fork") but did not formally publish descriptions. The specimens were not illustrated until 1847, when they were interpreted as the hypostome of the trilobite "Prionocheilus". Antonin Fritsch was the first to formally describe "Furca" as a distinct taxon, interpreting "F. bohemica" as a larval echinoderm in 1908. In 1919, "F. bohemica" was, for the first time, interpreted as an arthropod. A second species, "F. pilosa" was described in 1999, as well as an unnamed species simply called ""Furca" sp.". In 2013, Rak and colleagues suggested that "F. pilosa" and all previously named species were synonyms of "Furca bohemica".
A tentative additional species, "F. mauretanica" from the Floian stage Upper Fezouata formation of Morocco, was proposed in a doctoral thesis in 2006 and subsequently referred to as "probably belonging to the genus "Furca"". However, the name has yet to be formally published and so remains a "nomen nudum".