''Biceratops'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of olenelloid

redlichiid Redlichiida is an order of trilobites, a group of extinct marine arthropods. Species assigned to the order Redlichiida are among the first trilobites to appear in the fossil record, about halfway during the Lower Cambrian. Due to the difficulty ...

trilobites Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the At ...

, of average size, with the largest specimen long, not including the huge pleural spines of the 3rd segment of the thorax. It lived during the

Toyonian Cambrian Stage 4 is the still unnamed fourth stage of the Cambrian and the upper stage of Cambrian Series 2. It follows Cambrian Stage 3 and lies below the Wuliuan. The lower boundary has not been formally defined by the International Commission on ...

stage (last phase of the Upper ''Olenellus''-zone), in what is today the South-Western United States. ''Biceratops'' can easily be distinguished from other members of Biceratopsidae by the absence of genal spines, in combination with effaced features of the raised axial area of the head shield (or

glabella The glabella, in humans, is the area of skin between the eyebrows and above the nose. The term also refers to the underlying bone that is slightly depressed, and joins the two brow ridges. It is a cephalometric landmark that is just superior to ...

), that is bordering the two horn-like projections that carry the eyes. ''Biceratops nevadensis'' is the only known species in this genus (i.e. the genus is

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

Etymology

The name of the genus is derived from

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

and means ‘two horned-eyes’. The species

epithet An epithet (, ), also byname, is a descriptive term (word or phrase) known for accompanying or occurring in place of a name and having entered common usage. It has various shades of meaning when applied to seemingly real or fictitious people, di ...

refers to the US state where it was collected.

Description

As with most early trilobites, ''Biceratops'' has an almost flat

exoskeleton An exoskeleton (from Greek ''éxō'' "outer" and ''skeletós'' "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton (endoskeleton) in for example, a human. In usage, some of the ...

, that is only thinly calcified. It also shares crescent-shaped eye ridges, but these rise above the exoskeleton. As part of the Olenellina suborder, ''Biceratops'' lacks dorsal sutures. Like all other members of the Olenelloidea superfamily, the eye-ridges spring from the back of the frontal lobe (L4) of the central area of the cephalon, that is called

. The exoskeleton of ''Biceratops'' is ovate in outline and up to 8 cm in length, disregarding the huge pleural spines of the 3rd thorax segment. The head shield (or

cephalon Cephalon, Inc. was an American biopharmaceutical company co-founded in 1987 by pharmacologist Frank Baldino, Jr., neuroscientist Michael Lewis, and organic chemist James C. Kauer—all three former scientists with the DuPont Company. Baldino s ...

) is semicircular to subtriangular, about twice as wide as long. It has a distinct cephalic border. The glabella is hourglass-shaped and the furrows are indistinct. The small eyes are set on the vertical outside surface of the eyelobes (or palpebral lobes), that extend upwards and backwards above the glabella. The cheeks (or genae) are clearly convex. The thorax is about as long as wide and shaped as a shield. The frontal thorax (or prothorax) has 15 segments, the last of which carries a firm, long, backward-directed spine. The 3rd thorax segment is enlarged, the pleura at the axis slightly longer than that of other segments, and about four times as long at the side removed from the axis. Neighbouring pleurae are displaced because of the large pleurae of the 3rd segment. The back thorax (or opistothorax) consists of about 10 progressively smaller segments with insignificant pleurae. Tail shield (or pygidium) not known.

Differences with other Biceratopsinae

All other

Biceratopsinae The Biceratopsinae is an extinct subfamily of redlichiid trilobites within the family Biceratopsidae, with species of small to average size. Species belonging to this subfamily lived during the Toyonian stage (Upper ''Olenellus''-zone), 516-513 ...

have genal spines.

Distribution

''Biceratops nevadensis'' is known only from the lower part of the

Pioche Shale The Pioche Shale is an Early to Middle Cambrian Burgess shale-type Lagerstätte in Nevada. It spans the Early–Middle Cambrian boundary; fossils from the Early Cambrian are preserved in botryoidal hematite, whereas those from the Middle Cambria ...

( Upper ''Olenellus''-zone) at the base of the Frenchman Mountain, Clark County, Nevada.

Habitat

''Biceratops nevadensis'' was probably a marine bottom dweller, like all Olenellina.

Ecology

''Biceratops nevadensis'' occurs together with '' Olenellus fowleri, O. gilberti, O. terminatus'' and '' Mesonacis fremonti''.

References

{{Taxonbar, from=Q4903580 Redlichiida genera Biceratopsidae Cambrian trilobites of North America Fossils of the United States Cambrian genus extinctions