{{Short description|Extinct family of trilobites}} {{Automatic taxobox | fossil_range = {{Geological range|522|510|Botomian/Toyonian (''Olenellus''-zone)}} | image = Olenellus fowleri CRF.jpeg | image_caption = ''Olenellus fowleri'' | display_parents = 2 | taxon = Olenellidae | authority = Walcott, 1890 | subdivision_ranks = Subfamilies | subdivision = * Olenellinae * Mesonacinae }}
'''Olenellidae''' is an extinct family of redlichiid trilobite arthropods. Olenellids lived during the late Lower Cambrian (Botomian/Toyonian) in the ''Olenellus''-zone in the former paleocontinent of Laurentia<ref name='Lieberman 1999'/> and parts of what became the Famatinian orogen in what is now Argentina.<ref>{{cite journal |last1=Dalla Salda |first1=Luis H.|last2=Dalziel |first2=Ian W.D.|last3=Cingolani |first3=Carlos A.|last4=Varela |first4=Ricardo |date=1992 |title=Did the Taconic Appalachians continue into southern South America? |journal=Geology |volume=20 |issue=12 |pages=1059–1062 |doi= 10.1130/0091-7613(1992)020<1059:dttaci>2.3.co;2|bibcode=1992Geo....20.1059D |s2cid=128856492 |url=http://sedici.unlp.edu.ar/handle/10915/137929 }}</ref> This family can be distinguished from most other Olenellina by the partial merger of the frontal (L3) and middle pair (L2) of lateral lobes of the central area of the cephalon, that is called glabella, creating two isolated slits.<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://peabody.yale.edu/sites/default/files/documents/scientific-publications/ypmB45_1999.pdf|access-date=2012-10-30|archive-date=2019-05-09|archive-url=https://web.archive.org/web/20190509161341/http://peabody.yale.edu/sites/default/files/documents/scientific-publications/ypmB45_1999.pdf|url-status=dead}}</ref><!--- Including an explanatory schematic would help to understand this feature. ---><!--- Have to identify the "few Biceratopsinae" that share this feature and add a discriminating feature with the species concerned.---><!--- This character is absent in Mesonacis hyperborea. --->
== Key to the subfamilies == {| |- valign="top" align="left" ! scope="row" width="3%" | '''1''' | The angle in the back rim of the cephalon is less than 15°. Genal spines are reaching back no further than the 6th thorax segment. Spine on the 15th thorax segment almost as wide as the axis.<ref name='Lieberman 1999'/> <br>→ '''Olenellinae''' |- valign="top" align="left" ! scope="row" width="3%" | '''-''' | The angle in the back rim of the cephalon is more than 25°. Genal spines are reaching back at least to the 8th thorax segment. spine on the 15th thorax segment less than half as wide as the axis.<ref name='Lieberman 1999'/><br>→ '''Mesonacinae''' |}
== References == {{Reflist}}
{{Portal|Paleontology}} {{Taxonbar|from=Q1224048}}
Category:Olenellidae Category:Olenelloidea Category:Trilobite families Category:Cambrian first appearances Category:Cambrian Series 2 extinctions
{{Redlichiida-stub}}