Nevadia

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Nevadia
Temporal range: Atdabanian 524–521Ma
NevadiaSp.jpg
Nevadia sp., © Sam Gon III
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Trilobita
Order: Redlichiida
Suborder: Olenellina
Superfamily: "Nevadioidea"[1]
Family: "Nevadiidae"
Genus: Nevadia
Walcott, 1910
Species
  • N. weeksi Walcott, 1910 (Type)
  • N. addyensis Okulitch, 1951
  • N. faceta (Fritz, 1972)
  • N. fritzi Lieberman, 2001
  • N. gracile (Walcott, 1910)
  • N. ovalis McMenamin, 1987
  • N. parvoconica Fritz, 1992
  • N. saupeae Gapp, 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.

Etymology[edit]

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[edit]

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.[2]

Distribution[edit]

Nevadia weeksi from the Poleta Formation

Taxonomic[edit]

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

Species previously assigned to Nevadia[edit]

Habitat[edit]

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

References[edit]

  1. ^ Lieberman, B. S. (1998). "Cladistic Analysis of the Early Cambrian Olenelloid Trilobites". Journal of Paleontology 72 (1): 59–78. 
  2. ^ H. B. Whittington et al. (1997). "Introduction, Order Agnostida, Order Redlichiida". Treatise on Invertebrate Paleontology. Part O, Revised. Trilobita. 
  3. ^ a b 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". Zootaxa (2918): 15–28. ISSN 1175-5334. Retrieved 21 November 2012. 
  4. ^ a b 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 [1]
  5. ^ a b 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.[2][3]
  6. ^ 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 Paleontology 69 (4): 708–723 [4]
  7. ^ 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.[5]
  8. ^ J.J. Sepkoski Jr. 1998