''Furca'' (

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

for "fork") is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

marrellomorph Marrellomorpha are an extinct group of arthropods known from the Cambrian to the Early Devonian. They lacked mineralised hard parts, so are only known from Lagerstätte, areas of exceptional preservation, limiting their fossil distribution. The b ...

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

known from the Sandbian stage (upper

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ...

period) of the

Czech Republic The Czech Republic, also known as Czechia, and historically known as Bohemia, is a landlocked country in Central Europe. The country is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the south ...

, with a single currently described species, ''Furca bohemica''. A tentative additional species, "Furca mauretanica": was proposed for specimens discovered in

Morocco Morocco, officially the Kingdom of Morocco, is a country in the Maghreb region of North Africa. It has coastlines on the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to Algeria–Morocc ...

, but this species remains a ''

nomen nudum In Taxonomy (biology), taxonomy, a ''nomen nudum'' ('naked name'; plural ''nomina nuda'') is a designation which looks exactly like a scientific name of an organism, and may have originally been intended to be one, but it has not been published ...

'' until formally published, and probably belongs in a new separate genus.

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 crab Horseshoe crabs are arthropods of the family Limulidae and the only surviving xiphosurans. Despite their name, they are not true crabs or even crustaceans; they are chelicerates, more closely related to arachnids like spiders, ticks, and scor ...

s suggest a benthic marine lifestyle: dwelling on the sea floor.

Classification

With its unusual anatomy, ''Furca'' has a colorful taxonomic history. The first specimens were discovered by

Joachim Barrande Joachim Barrande (11 August 1799 – 5 October 1883) was a French geologist and palaeontologist. He was particularly known for his work on trilobites, published in the ''Systéme Silurien de la Bohéme'' which he published in 22 parts. Trained und ...

, who named them ''Furca bohemica'' (Latin for "

Bohemia Bohemia ( ; ; ) is the westernmost and largest historical region of the Czech Republic. In a narrow, geographic sense, it roughly encompasses the territories of present-day Czechia that fall within the Elbe River's drainage basin, but historic ...

n fork") but did not formally publish descriptions. The specimens were not illustrated until 1847, when they were interpreted as the

hypostome In zoology, the hypostome can refer to structures in distinct animal groups: *Hypostome (trilobite), the ventral mouthpart plate in trilobites *Hypostome (tick) The hypostome (also called the maxilla, radula, or Labium (insect), labium) is a Os ...

of the

trilobite Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most succ ...

'' Prionocheilus''. Antonin Fritsch was the first to formally describe ''Furca'' as a distinct taxon, interpreting ''F. bohemica'' as a larval

echinoderm An echinoderm () is any animal of the phylum Echinodermata (), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as ...

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 A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

of ''Furca bohemica''. A tentative additional species, "Furca mauretanica" from the

Floian The Floian is the second stage of the Ordovician Period. It succeeds the Tremadocian with which it forms the Lower Ordovician series. It precedes the Dapingian Stage of the Middle Ordovician. The Floian extended from to million years ago. The ...

stage

Fezouata Formation The Fezouata Formation or Fezouata Shale is a geological formation in Morocco which dates to the Ordovician, Early Ordovician.

, 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 ''

''. Phylogenetic analyses have recovered it as distinct marrelid taxon not closely related to ''Furca bohemica,'' and thus probably should be placed in a separate genus. ''Furca bohemica'' is assigned to the

clade Marrellida. While historicaly placed in Mimetasteridae alongside '' Mimetaster'', other studies have disputed this placement.

References

{{Taxonbar, from=Q18164850 Marrellomorpha Prehistoric arthropod genera Fossils of the Czech Republic Letná Formation Ordovician arthropods Fezouata Formation fossils Fossil taxa described in 1908 Ordovician genus extinctions