| 词条 | Nevadella |
| 释义 |
| 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[1] | familia = "Nevadiidae" | genus = Nevadella | genus_authority = Raw, 1936 | subdivision_ranks = Species | subdivision =
}}Nevadella 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.[3] EtymologyThe name is derived from Nevadia, a related genus. TaxonomyNevadia predates Nevadella and may include its direct ancestor. Species previously assigned to Nevadella
DescriptionThe 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 silhuette 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.[4] DistributionFossils of Nevadella have been found in the late Atdabanian of the USA (California, Nevada) and Canada (Cordilleran region).
EcologyContemporary taxa that also occur in the so-called "Nevadella" Zone include Esmeraldina, Holmiella, Palmettaspis, Bradyfallotaspis, Geraldinella, Paranevadella, Nevadia, Buenellus, and Cirquella.[4] HabitatNevadella species were probably marine bottom dwellers, like all Olenellina. References1. ^{{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|url=http://invitestock.free.fr/Cambrien/pdf/Spanish%20fauna/Cladistic%20Analysis%20of%20the%20Early%20Cambrian%20Olenelloid%20Trilobites.pdf}} {{Taxonbar|from=Q7003688}}2. ^{{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%APAOTOW>2.0.CO;2}} 3. ^{{cite journal | last = Sepkoski| first = Jack| authorlink =| title = A compendium of fossil marine animal genera (Trilobita entry)| journal = Bulletins of American Paleontology| volume = 364| issue =| page = 560| publisher =| location =| year = 2002| url = http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=307&rank=class| doi =| id =| accessdate = 2008-01-12 }} 4. ^1 {{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}} 5. ^Paleobiology Database 6. ^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. 7. ^Life Desks, Trilobites on line 8. ^Life Desks, Trilobites on line 9. ^U. S. National Museum, Catalogue No. 60082. 4 : Redlichioidea|Cambrian trilobites of North America|Paleozoic life of Alberta|Paleozoic life of British Columbia |
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