Nevadella
{{Short description|Extinct genus of trilobites}}
{{taxobox
| fossil_range = Late Atdabanian, {{Geological range|524|522}}
| image = Nevadella eucharis USNM PAL 60079.jpg
| image_caption = Nevadella eucharis, type specimen
| regnum = Animalia
| phylum = Arthropoda
| classis = Trilobita
| ordo = Redlichiida
| superfamilia = Nevadioidea{{cite journal|last1= Lieberman|first1= B.S.|year= 1998|title= Cladistic Analysis of the Early Cambrian Olenelloid Trilobites|journal= Journal of Paleontology|volume= 72|issue= 1|pages= 59–78|doi= 10.1017/S0022336000024021|bibcode= 1998JPal...72...59L|s2cid= 86307339|url=http://invitestock.free.fr/Cambrien/pdf/Spanish%20fauna/Cladistic%20Analysis%20of%20the%20Early%20Cambrian%20Olenelloid%20Trilobites.pdf}}
| familia = "Nevadiidae"
| genus = Nevadella
| genus_authority = Raw, 1936
| subdivision_ranks = Species
| subdivision =
- N. eucharis (Walcott, 1913) (type) synonym Callavia eucharis
- N. baculenta (Fritz, 1972)
- N. cartlandi (Raw in Walcott, 1910) synonyms Callavia cartlandi, C. cobboldi, C. brevioculata{{cite journal|last= Lieberman|first= B. S.|year= 2001|title= Phylogenetic Analysis of the Olenellina Walcott, 1890 (Trilobita, Cambrian)|journal= Journal of Paleontology|volume= 75|number= 1|pages= 96–115|url= http://www.bioone.org/doi/full/10.1666/0022-3360%282001%29075%3C0096%APAOTOW%3E2.0.CO%3B2|doi=10.1666/0022-3360(2001)075<0096:PAOTOW>2.0.CO;2|s2cid= 85656419|url-access= subscription}}
- N. keelensis Abe, 2010
- N. mountjoyi (Fritz, 1972)
- N. perfecta (Walcott, 1913) synonym Callavia perfecta
}}
Image:Nevadella perfecta USNM PAL 60082.jpgNevadella is an extinct genus of trilobites, fossil marine arthropods, with species of average size (about {{convert|5|cm|in|disp=or}} long). It lived during the late Atdabanian stage, which lasted from 530 to 524 million years ago during the early part of the Cambrian Period.{{cite journal | last = Sepkoski| first = Jack| title = A compendium of fossil marine animal genera (Trilobita entry)| journal = Bulletins of American Paleontology| volume = 364| page = 560| year = 2002| url = http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=307&rank=class| access-date = 2008-01-12 }}
Etymology
The name is derived from Nevadia, a related genus.
Taxonomy
Nevadia predates Nevadella and may include its direct ancestor.
= Species previously assigned to ''Nevadella'' =
- N. burri = Pleisionevadella burri
Description
The body of Nevadella is very flat dorso-ventrally. The general outline of its thin, lightly calcified exoskeleton is inverted 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 wedging out slightly in the frontal half and with a rounded front (like the silhouette of a slim pawn). The glabella and the frontal margin almost or entirely touch (in jargon: the preglabellar field is short or absent). Cephalic margin at least as wide as the most frontal thoracal segment. The thorax has 17 to 23 segments, gradually diminishing in size. The pleural spines are long and sickle-shaped. The tailshield (or pygidium) is very small and subquadrate in shape.{{cite book |author=H. B. Whittington|title=Treatise on Invertebrate Paleontology. Part O, Revised. Trilobita |chapter=Introduction, Order Agnostida, Order Redlichiida |year=1997|display-authors=etal}}
Distribution
Fossils of Nevadella have been found in the late Atdabanian of the USA (California, Nevada) and Canada (Cordilleran region).
- N. eucharis is known from the Middle Member of the Poleta Formation, Esmeralda County, Nevada, USA.[http://paleodb.geology.wisc.edu/cgi-bin/bridge.pl?action=basicCollectionSearch&collection_no=10496 Paleobiology Database]
- N. keelensis is known from the Sekwi Formation, Northwest Territories, Canada.F. R. Abe, B. S. Lieberman, M. C. Pope, K. Dilliard (2010). "New information on olenelline trilobites from the Cambrian Sekwi Formation in northwestern Canada". Canadian Journal of Earth Sciences, 2010, 47 (12): 1445–1449.[http://www.nrcresearchpress.com/doi/abs/10.1139/E10-073][http://trilobites.lifedesks.org/node/690 Life Desks, Trilobites on line]
- N. mountjoyi is known from the Mural Formation, north slope of Mount Mumm, Alberta, Canada.[http://trilobites.lifedesks.org/node/696 Life Desks, Trilobites on line]
- N. perfecta is known from the Mahto Formation, Mumm Peak on the west side of Hitka Pass, western Alberta, Canada.U. S. National Museum, Catalogue No. 60082.
Ecology
Contemporary taxa that also occur in the so-called "Nevadella" Zone include Esmeraldina, Holmiella, Palmettaspis, Bradyfallotaspis, Geraldinella, Paranevadella, Nevadia, Buenellus, and Cirquella.
Habitat
Nevadella species were probably marine bottom dwellers, like all Olenellina.