{{Short description|Extinct genus of trilobites}} {{Automatic taxobox | fossil_range = Late Atdabanian,<br>{{Geological range|524|522}} | taxon = Cirquella | authority = Fritz, 1993 | subdivision_ranks = Species | subdivision = * ''C. nummularia'' <small>Fritz, 1993 (Type)</small> * ''C. espinata'' <small>Fritz, 1993</small> * ''C. nelsoni'' <small>Lieberman, 2001</small> }}
'''''Cirquella''''' is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the Atdabanian stage,<ref name="Sepkoski 2002"/> in the former continent Laurentia.<ref name='Whittington'>{{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}}</ref>
== Description == Only the thin and lightly calcified headshields (or cephalon) of ''Cirquella'' have ever been found. It is very flat, almost oval in outline, the length about 85% of the width. The central area of the cephalon (or glabella) is moderately tapered forward. The furrows dividing the glabella are only weakly developed. The back of the eye ridge is opposite the first lobe (L1) of the glabella in front of the band (or occipital ring) at the back of the glabella.<ref name='Whittington'/> In ''Cirquella espinata'' there is no genal spine but a slight angularity of margin opposite first lobe in front of the occipital ring. In ''Cirquella nummularia'' the rim of the cephalon is entirely rounded.<ref name='Fritz'>{{cite journal |last1=Fritz |first1=W. H. |title=New Lower Cambrian olenelloid trilobite genera ''Cirquella'' and ''Geraldinella'' from southwestern Canada |journal=Journal of Paleontology |date=1993 |volume=67 |issue=5 |pages=856–868 |doi=10.1017/S0022336000037112 |bibcode=1993JPal...67..856F }}</ref>
== Distribution == ''C. nummularia'' is known from the earliest half of the Lower ''Nevadella'' Zone, in the Dogtooth Mountains, British Columbia, Canada, and in Nevada.<br> ''C. espinata'' lived at the same time in the Southern Canadian Rocky Mountains.<ref name='Fritz'/><br> ''C. nelsoni'' is reported from the ''Fallotaspis''-''Judomia'' Faunule, ''Fallotaspis'' Biozone, Campito Formation, Inyo-White Mountains, Eastern California.<ref>[http://www.westerntrilobites.com/Species/C.nelsoni.htm Western Trilobite Association website]</ref>
== Habitat == ''Cirquella'' species were probably marine bottom dwellers, like all Olenellina.
== References == {{Reflist|refs= <ref name="Sepkoski 2002">{{cite journal |last=Sepkoski |first=Jack |title=A compendium of fossil marine animal genera |journal=Bulletins of American Paleontology |volume=363 |pages=5–560 |date=2002 |url=https://www.biodiversitylibrary.org/item/40634#page/5/mode/1up |isbn=978-0-87710-450-6 }}</ref> }}
== Sources == * {{cite journal |last1=Lieberman |first1=Bruce S. |title=Phylogenetic analysis of some basal early Cambrian trilobites, the biogeographic origins of the Eutrilobita, and the timing of the Cambrian radiation |journal=Journal of Paleontology |date=2002 |volume=76 |issue=4 |pages=692–708 |doi=10.1666/0022-3360(2002)076<0692:PAOSBE>2.0.CO;2 |jstor=1307101 }} {{Taxonbar|from=Q5121980}}
Category:Olenellina Category:Redlichiida genera Category:Cambrian trilobites Category:Fossils of British Columbia Category:Fossils of the United States
{{redlichiida-stub}}