''Nevadia'' 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 ...

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 ...

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

marine

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...

s, with species of average size (about long). It lived during the

Atdabanian Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approx ...

stage, which lasted from 530 to 524 million years ago, in what are today Western Canada, the Western United States, and Mexico.

Etymology

''Nevadia'' is named for the US State of Nevada, where the first specimens of this genus where found. ''N. fritzi'' in named in honor of W.H. Fritz, a paleontologist who worked on olenelloid trilobites.

Description

The body of ''Nevadia'' is very flat dorso-ventrally. The general outline of its thin, lightly calcified

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 ...

is inverted wide drop-shaped. The front is rounded, widest at the back of the headshield (or cephalon), and tapering from there to an eventually rounded termination. The central area of the cephalon (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 ...

) is distinctly tapered forward, sides slightly concave, but not wedging out in the frontal half and with a narrow rounded front. The glabella and the frontal margin do not touch (in jargon: the preglabellar field is present). Cephalic margin clearly less wide as the most frontal thoracal segment. The

thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...

has 27 segments. The segments look a bit degenerated behind the 15th to 18th (or an opisthothorax can be distinguished). The pleural spines are long and sickle-shaped. The tailshield (or

pygidium The pygidium (plural pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is compo ...

) is very small and subquadrate in shape.

Distribution

*''Nevadia ovalis'' occurs in the Lower Cambrian of the Northwest Territories, Canada (Sekwi Formation, Mackenzie Mountains), and Mexico (Senora). *''Nevadia parvoconica'' and ''Nevadia sp.'', have been collected at the Mural Formation, Mumm Peak Section, Canada, .W. H. Fritz. 1992. "Walcott's Lower Cambrian Olenellid trilobite collection 61k, Mount Robson Area, Canadian Rocky Mountains". ''Geological Survey of Canada Bulletin'' 432. 1–6

/ref> *''Nevadia weeksi'' and ''Nevadia sp.'', were found at Cinnamon Peak-Whitehorn Mountain, Section, Mural Formation, Canada, ; and at the Montenegro Member, Campito Formation, Esmeralda County, Nevada, USA.J. S. Hollingsworth (1999). "A second candidate position for the base of the Montezuman". ''Laurentai'' 99: V field conference of the Cambrian Stage Subdivision Working Group, International Subcommission on Cambrian Stratigraphy 42–4

http://paleodb.geology.wisc.edu/cgi-bin/bridge.pl?action=basicCollectionSearch&collection_no=10496] *''Nevadia weeksi'' occurs near the base of the Montenegro Member, Campeto Formation, Northeast of Barrel Spring, Nevada, USA, . *''Nevadia sp.'', was collected at Puerto Blanco, Unit 3, Cerro Rajon, Caborca Region, Mexico, ; and at the ''Nevadella'' zone, Old Dominion Limestone Formation, Colville, Washington, USA, .J.J. Sepkoski Jr. 1998
/ref> *''Nevadia parvoconica'', was found at the Middle Member of the Poleta Formation, Esmeralda County, Nevada, USA. *''Nevadia saupeae'', was recovered from the Sekwi Formation, Mackenzie Mountains, Northwest Territories, Canada

Taxonomic

''Nevadia'' predates ''Nevadella'' and according to cladistic analysis includes its direct ancestor.

Species previously assigned to Nevadia

* ''Nevadia crosbyi'' = '' Callavia, Callavia broegeri''

Habitat

''Nevadia'' species were probably marine bottom dwellers, like all Olenellina.

References

{{Taxonbar, from=Q1217366 Redlichioidea Redlichiida genera Cambrian trilobites Cambrian trilobites of North America Paleontology in Washington (state) Paleozoic life of Alberta Paleozoic life of British Columbia