Nephrolenellus

{{Short description|Genus of trilobites}} {{Italic title}} {{Automatic_taxobox | fossil_range = Toyonian (Upper ''Olenellus-zone'') {{Geological range|516|513}} | image = Nephrolenellus geniculatus left light CRF.jpg | image_caption = juvenile ''Nephrolenellus multinodus'', 9mm, frontal glabellar lobe broken | taxon = Nephrolenellus | authority = Palmer & Repina, 1993 | subdivision_ranks = Species | subdivision = * ''Nephrolenellus multinodus'' <small>(Palmer in Palmer and Halley, 1979) (Type)</small> synonyms ''Olenellus multinodus'', ''N. jasperensis''<ref name='Lieberman 1999'>{{cite journal|last1= Lieberman|first1=B.S.|year=1999|title=Systematic Revision of the Olenelloidea (Trilobita, Cambrian)|journal=Bulletin of the Peabody Museum of Natural History|volume=45|url=http://invitestock.free.fr/Cambrien/pdf/Spanish%20fauna/Cladistic%20Analysis%20of%20the%20Early%20Cambrian%20Olenelloid%20Trilobites.pdf}}</ref> * ''Nephrolenellus geniculatus'' <small>Palmer, 1998</small><ref name='Webster 2007'/> }}

'''''Nephrolenellus''''' is an extinct genus of trilobite, fossil marine arthropods, of relatively small size (sagittal length of cephalon rarely exceeds 11 mm). Currently two species are attributed to it. ''Nephrolenellus'' lived at the end of the Lower Cambrian. Species are known from the Great Basin of California, Nevada and Arizona, with one specimen from Canada.<ref name='Webster 2007'>{{cite journal|first= Webster|last= M.|year= 2007|title= Ontogeny and evolution of the early Cambrian trilobite genus ''Nephrolenellus'' (Olenelloidea)|journal= Journal of Paleontology|volume= 81|issue= 6|pages= 1168–1193|url=http://jpaleontol.geoscienceworld.org/cgi/content/full/81/6/1168|doi=10.1666/06-092.1|bibcode= 2007JPal...81.1168W|s2cid= 85652241|url-access= subscription}}</ref>

== Taxonomy == ''N. geniculatus'' may have been a direct descendant of ''N. multinodus''.<ref name='Webster 2007'/>

== Distribution == ''Nephrolenellus multinodus'' occurs in the late Lower Cambrian of California (Toyonian, Pyramid Shale Member, Carrara Formation, Inyo County, 35.8° N, 116.2° W).<ref>{{cite conference|author=E.D. Fowler|year= 1999|title= Biostratigraphy of upper Dyeran strata of the Carrara Formation, Emigrant Pass, Nopah Range, California|conference= Laurentia 99: V field conference of the Cambrian Stage Subdivision Working Group, International Subcommission on Cambrian Stratigraphy|pages= 46–50}}</ref> and of Nevada (Toyonian, Lincoln County; and C-Shale Member, Pioche Formation, Ruin Wash, Chief Range, 37.8° N, 114.6° W).<ref name='Palmer'>{{cite journal|last1=Palmer |first1=A.R.|year=1998|title=Terminal Early Cambrian Extinction of the Olenellina: Documentation from the Pioche Formation, Nevada|journal=Journal of Paleontology|volume=72|issue=4|pages=650–672|doi=10.1017/S0022336000040373 |jstor=1306693|bibcode=1998JPal...72..650P |s2cid=131861504 }}</ref>

== Description == thumb|left| Reconstructions of ''N. multinodus'' (L), ''N. genticulatus'' (R). As with most early trilobites, ''Nephrolenellus'' has an only thinly calcified exoskeleton. Although most of the body is rather flat, the frontal lobe (L4) of the central area of the cephalon (or glabella) is raised, but not bulbous, and does not overlap the border at the front in dorsal view. It also has the crescent-shaped ocular lobes typical for the earliest trilobites. As part of the Olenellina suborder, ''Nephrolenellus'' lacks dorsal sutures. Like all other members of the Olenelloidea superfamily, the ocular lobes extend from the back of the frontal lobe (L4) of the glabella. Typically for ''Nephrolenellus'' the eyeridges are pointing backwards and significantly (45°) outwards (along the tangent between the base and termination). The glabella is strongly constricted at the second pair of glabellar lobes (L2). The furrow between the second and third pair of lobes (S2) is transverse or gently convex anteriorly. S3 is pit-like and isolated from the furrow defining the glabella (or axial furrow). The spine at the outer backside of the cephalon is longer than the most backward lobe of the glabella (also called occipital ring or L0), and it is based at the point the cephalon is at its widest. The prothorax consists of thirteen segments, and the third segments are macropleural, each carrying a trailing spine at the side that is comparable in length to the entire exoskeleton. It lacks the long axial spine where prothorax ends. The portion of the thorax where the pleural lobes are reduced (or opisthothorax) consists of at least 23 segments.

== References == {{Reflist}}

Category:Cambrian trilobites of North America Category:Redlichiida genera Category:Biceratopsidae Category:Cambrian genus extinctions