Meniscuchus

{{Short description|Extinct genus of trilobites}} {{Automatic taxobox | fossil_range = {{Geological range|522|516|Botomian}} | taxon = Meniscuchus | authority = Öpik, 1975 | subdivision_ranks = Species | subdivision = * ''M. menetus'' Öpik, 1975 (type) * ''M. fissifrons'' (Rasetti, 1966) synonym ''Calodiscus fissifrons'' * ''M. helena'' (Walcott, 1889) synonyms ''Microdiscus helena'', ''Acimetopus helena'', ''Calodiscus helena'' * ''M. nanus'' (Palmer, 1968) synonym ''Calodiscus nanus'' * ''M. reticulata'' (Rasetti, 1966) }}

'''''Meniscuchus''''' is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the Botomian stage,<ref name="Sepkoski">{{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 |accessdate=12 January 2008 |url-status=dead |archiveurl=https://web.archive.org/web/20060905162524/http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=307&rank=class |archivedate=5 September 2006 }}</ref> which lasted from approximately 522 to 516 million years ago. This faunal stage was part of the Cambrian Period. ''Meniscuchus'' has been found in the USA (Alaska, New York), Canada (Newfoundland, Quebec), Russia (Siberian Platform, Gorno-Altayskaya) and Australia (New South Wales).<ref name='Treatise'>Whittington, H. B. et al. Part O, Treatise on Invertebrate Paleontology. Revised, Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida. 1997</ref>

== Distribution == * ''M. helena'' has been found in the Lower Cambrian of Canada (Newfoundland).<ref name='Öpik'>{{cite journal|last= Öpik|first= A.A.|year= 1975|title= Cymbric Vale Fauna of New South Wales and Early Cambrian Biostratigraphy|journal= BMR Bulletin|volume= 159|pages= 1–32|url= http://www.ga.gov.au/webtemp/1328168/Bull_159.pdf}}</ref> * ''M. menetus'' is known from the Lower Cambrian of Australia (Cymbric Vale Formation, New South Wales).<ref name='Treatise'/> * ''M. nanus'' was collected in Alaska.<ref name='Öpik'/>

== Description == Like all Eodiscina, the headshield (or cephalon) and tailshield (or pygidium) are approximately equal in size. Like all Weymouthiidae, ''Meniscuchus'' is eyeless and lacks free cheeks. The axis of the cephalon (or glabella) is wide at its base (that is, where it would touch the thorax) and is rounded at the front, where it touches the border furrow. The glabella is divided by two furrows crossing the glabella, creating a frontal lobe (L4) more than twice as long (along the axis) as its narrow neighbour (L3). Further lobes (L2 and L1) may be suggested by a faint dent in the furrow defining the outline of the glabella. At the back the glabella is terminated by a narrow occipital ring (L0), extended backwards at midline with its margin a semicircle. The cephalic border is almost as wide as L4, but is only half as wide laterally while becoming slightly wider again further back. Thorax probably with three segments.<ref name='Öpik'/> Its pygidium is relatively long. Its axis is tapering and reaching the border furrow at midline, and is deeply segmented with 4 to 10 axial rings. The pleural areas are unfurrowed. The border of the pygidium is uniformly narrow. The doublure is wide and almost vertical.<ref name='Treatise'/>

==References== {{Reflist}}

Category:Weymouthiidae Category:Agnostida genera Category:Cambrian trilobites of North America Category:Cambrian trilobites of Australia Category:Cambrian genus extinctions