Nevadia

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Nevadia
Temporal range: Atdabanian 524–521  Ma
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NevadiaSp.jpg
Nevadia sp.
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Arthropoda
Class: Trilobita
Order: Redlichiida
Suborder: Olenellina
Superfamily: Nevadioidea
Family: Nevadiidae
Genus: Nevadia
Walcott, 1910
Species
  • N. weeksiWalcott, 1910 (Type)
  • N. addyensisOkulitch, 1951
  • N. faceta(Fritz, 1972)
  • N. fritziLieberman, 2001
  • N. gracile(Walcott, 1910)
  • N. ovalisMcMenamin, 1987
  • N. parvoconicaFritz, 1992
  • N. saupeaeGapp, 2011

Nevadia is an extinct genus of trilobites, fossil marine arthropods, with species of average size (about 3.5 centimetres or 1.4 inches long). It lived during the Atdabanian stage, which lasted from 530 to 524 million years ago, in what are today Western Canada, the Western United States, and Mexico.

Contents

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 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) 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 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) is very small and subquadrate in shape. [1]

Distribution

Nevadia weeksi from the Poleta Formation Nevadia weeksi CRF.jpg
Nevadia weeksi from the Poleta Formation

Taxonomic

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

Species previously assigned to Nevadia

Habitat

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

Related Research Articles

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Emuellidae Extinct family of trilobites

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<i>Wanneria</i>

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Cirquella is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the Atdabanian stage, in the former continent Laurentia.

<i>Nevadella</i>

Nevadella is an extinct genus of trilobites, fossil marine arthropods, with species of average size. It lived during the late Atdabanian stage, which lasted from 530 to 524 million years ago during the early part of the Cambrian Period.

<i>Nephrolenellus</i>

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<i>Pagetia</i>

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Holmiidae

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Acmarhachis is a genus of trilobite in the order Agnostida, which lived in what are now Australia, Canada, China (Anhui), Kazakhstan, Russia (Kharaulakh), and the US. It was described by Resser in 1938, and the type species is Acmarhachis typicalis.

<i>Bristoliinae</i>

The Bristoliinae is an extinct subfamily of trilobites, fossil marine arthropods, with species of small to average size. Species belonging to this subfamily lived during the Botomian and Toyonian stage (Olenellus-zone), 522-513 million years ago, in the former continent of Laurentia, including what are today Mexico, the Appalachian Mountains and the south-western United States, and Canada.

Lochmanolenellus is an extinct genus of trilobites, fossil marine arthropods, with one small species, L. mexicana. It lived during the Botomian stage (Olenellus-zone), 522–513 million years ago, in the South-West of the former continent of Laurentia, in what are today Mexico, and the South-Western United States.

Bolbolenellus is an extinct genus of trilobites, fossil marine arthropods, with five species attributed to it currently. It can be easily distinguished from all other trilobites by the combination of the absence of dorsal sutures in the head shield like all Olenellina, and a distinctly bulbous frontal lobe (L4) of the raised axial area in the head called glabella. The species lived at the end of the Lower Cambrian.

<i>Mallagnostus</i>

Mallagnostus Howell, 1935, is a trilobite genus belonging to the family Weymouthiidae Kobayashi T. (1943), Order Agnostida Salter (1864) according to Whittington et al. 1997. It lived during the late Lower Cambrian, with remains found in USA, Canada (Newfoundland), Spain, England, Russia, Mongolia, and the early Middle Cambrian as reported from China and Russia (Yakutia).

<i>Thoracocare</i>

Thoracocare is a minute to very small trilobite, that lived during part of the Middle Cambrian in what are today the states of Idaho, Nevada and Utah. It is the only trilobite known with just two thorax segments outside most members of the Agnostida order. It can be distinguished from Agnostida by the very wide subquadrate glabella, parallel-side or widening forward in the largest specimen, with the full front side touching the border. Two species are known, one, T. idahoensis, only from pygidia.

<i>Cedaria</i>

Cedaria is a small, rather flat trilobite with an oval outline, a headshield and tailshield of approximately the same size, 7 articulating segments in the middle part of the body and spines at the back edges of the headshield that reach halflength of the body. Cedaria lived during the early part of the Upper Cambrian (Dresbachian), and is especially abundant in the Weeks Formation.

<i>Orygmaspis</i>

Orygmaspis is a genus of asaphid trilobite with an inverted egg-shaped outline, a wide headshield, small eyes, long genal spines, 12 spined thorax segments and a small, short tailshield, with four pairs of spines. It lived during the Upper Cambrian in what are today Canada and the United States.

William Harold Fritz was a geologist who worked for the Geological Survey of Canada. He is known for his work in stratigraphy and on olenelloid trilobites.

References

  1. H. B. Whittington; et al. (1997). "Introduction, Order Agnostida, Order Redlichiida". Treatise on Invertebrate Paleontology. Part O, Revised. Trilobita.
  2. 1 2 Gapp, I. Wesley; Lieberman, Bruce S.; Pope, Michael C.; Dilliard, Kelly A. (2011). "New olenelline trilobites from the Northwest Territories, Canada, and the phylogenetic placement of Judomia absita Fritz, 1973" (PDF). Zootaxa. 2918 (2918): 15–28. doi:10.11646/zootaxa.2918.1.2. ISSN   1175-5334 . Retrieved 21 November 2012.
  3. 1 2 W. H. Fritz. 1992. "Walcott's Lower Cambrian Olenellid trilobite collection 61k, Mount Robson Area, Canadian Rocky Mountains". Geological Survey of Canada Bulletin 432. 1–66
  4. 1 2 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 42–46.
  5. W. H. Fritz (1995). "Esmeraldina rowei and associated Lower Cambrian trilobites (1f fauna) at the base of Walcott's Waucoban Series, southern Great Basin, U.S.A." Journal of Paleontology69 (4): 708–723
  6. J. Stewart, M. A. S. McMenamin, and J. M. Morales-Ramirez (1984). "Upper Proterozoic and Cambrian rocks in the Caborca Region, Sonora, Mexico - physical stratigraphy, biostratigraphy, paleocurrent studies, and regional relations". U. S. Geological Survey Professional Papers (1309)1–33.
  7. J.J. Sepkoski Jr. 1998