Olenellus
Olenellus is an extinct genus of redlichiid trilobites, with species of average size. It lived during the Botomian and Toyonian stages of the Lower Cambrian,, in what is currently North America, part of the palaeocontinent Laurentia.
Etymology
[image:Olenellus fowleri CRF.jpeg|thumb|right|Olenellus fowleri was named in honor of Ed Fowler]Olenellus means small Olenus, after a genus belonging to the Ptychopariida, to which the type species O. thompsoni was originally assigned. The name Olenus refers to a mythological figure who was turned to stone by the gods. The names of the species have the following derivations.agellus comes from the Latin word for field or hamlet.chiefensis refers to the Chief Range, which includes the Ruin Wash section, that holds the last of the Olenellina.fowleri was named in honor of Ed Fowler, whose quarrying skills exposed the type locality of this species.getzi is called after, on whose Lancaster estate several Olenellus species were first collected.nevadensis refers to the state of Nevada, where this species is found.parvofrontatus means ‘small front’ from the Latin words parvus and frontatus, indicating the short distance between the anterior border and the glabella in this species.roddyi was named in honor of Dr. H. Justin Roddy, an internationally known naturalist, curator and professor of geology.romensis refers to the Rome Formation.terminatus is from the Latin terminus, meaning final, indicating the demise of the Olenellus lineage.Taxonomy
Relationship within the Olenellidae
Olenellus is the only genus currently recognised in the subfamily Olenellinae. The sister group called the Mesonacinae consists of the genera Mesonacis and Mesolenellus.[Image:Olenellus-fowleri.jpg|thumb|left|Olenellus fowleri collected from the Pioche Shale, Lincoln County, Nevada.]Status of the clade ''"Paedeumias"''
"Paedeumias" was previously regarded as a genus related to Olenellus or a subgenus being part of Olenellus. Recent analysis shows that there is a group of species formerly assigned to Olenellus nested within Olenellus. However, this group is more closely related to the majority of the remainder of Olenellus species than to O. agellus and O. romensis. This implies that either two new monophyletic subgenera need to be erected, or Olenellus and Olenellus need to be dropped as subgenera, the latter being proposed by Lieberman.Reassigned species
O. alabamensis = Fremontella halliO. altifrontatus = Bolbolenellus altifrontatusO. argentus pl. 40, fig 12, 13, 15, 16, non fig. 14 = Grandinasus argentusO. argentus pl. 40, fig 14, non fig. 12, 13, 15, 16 = Holmiella falxO. bondoni = Fallotaspis bondoni O. bonnensis = Mesonacis bonnensisO. brevoculus = Mesonacis bonnensisO. broegeri = Callavia broegeriO. bristolensis = Bristolia bristolensisO. bristolensis p. 8. fig 1-11, non pl. 7, fig 1, 2, 5 = Bristolia harringtoniO. bufrontis = Bolbolenellus sphaerulosusO. callavei = Callavonia callaveiO. cylindricus = Mesonacis cylindricusO. eagerensis = Mesonacis eagerensisO. euryparia = Bolbolenellus eurypariaO. forresti = Redlichia forrestiO. fremonti pl. 15, fig. 18 = Bristolia fragilisO. fremonti pl. 37, fig. 1, 4-5 = Bolbolenellus eurypariaO. fremonti pl. 37, fig. 1-2 = Mesonacis fremontiO. georgiensis, p. 220, pl. 5, fig. 7, non fig. 6 = Mesonacis vermontanusO. gigas = Andalusiana cornutaO. gilberti = Bristolia bristolensisO. groenlandicus = Bolbolenellus groenlandicusO. halli = Fremontella halliO. hamoculus = Mesonacis hamoculusO. hermani = Bolbolenellus hermaniO. hyperboreus = Mesolenellus hyperboreusO. insolens = Bristolia insolensO. intermedius = Fritzolenellus lapworthi or F. reticulatusO. kentensis = Bolbolenellus groenlandicusO. lapworthi = Fritzolenellus lapworthiO. laxocules = Elliptocephala laxoculesO. logani = Elliptocephala loganiO. mickwitzi = Schmidtiellus mickwitzi mickwitziO. mohavensis = Bristolia mohavensisO. multinodus = Nephrolenellus multinodusO. paraocules = Elliptocephala paraoculesO. praenuntius = Elliptocephala praenuntiusO. reticulatus = Fritzolenellus reticulatusO. sequomalus = Elliptocephala sequomalusO. sphaerulosus = Bolbolenellus sphaerulosusO. svalbardensis = Mesolenellus svalbardensisO. terranovicus = Mesonacis bonnensisO. torelli = Schmidtiellus mickwitzi torelliO. truemani = Elliptocephala walcottiO. truemani = Fritzolenellus truemaniO. truncatooculatus = Mummaspis truncatooculatusO. vermontanus = Mesonacis vermontanusO. walcottanus = ''Wanneria walcottana''Distribution
[Image:Olenellus gilbert rightlight CRF.jpg|thumb|right|Olenellus gilberti][Image:Olenellus yorkensis CRF.jpg|thumb|right|Olenellus roddyi]
O. thompsoni is found in the middle Upper Olenellus-zone of Vermont.
O. agellus is present in the middle Upper Olenellus-zone of Vermont.
O. chiefensis has been collected from the final layer of the Upper Olenellus-zone of Nevada.
O. clarki is found in Upper Olenellus-zone of California ; and in Nevada.
O. crassimarginatus has been collected in the middle Upper Olenellus-zone of Vermont ; and south of East Petersburg; north of York and Fruitville, north of Lancaster.
O. fowleri has been collected from the final layer of the Upper Olenellus-zone of Nevada.
O. getzi is found in Upper Olenellus-zone of Pennsylvania.
O. howelli occurs in the final layer of the Upper Olenellus-zone of Nevada.
O. nevadensis has been collected in the Upper Olenellus-zone, Bristolia-zonule of California ; and from the Latham Shale – treated as the Bristolia-zonule – at the south end of the Marble Mountains, near Chambless in the Mohave Desert portion of San Bernardino County. It also occurs in the Bristolia-zonule, Upper Olenellus-zone of Nevada.
O. parvifrontatus has been collected in the Olenellus-zone of the Yukon Territory, Canada.
O. puertoblancoensis was found in the Botonian/Toyonian Olenellus-zone of the Caborca Region, Mexico
O. robsonensis occurs in the ?Middle Olenellus-zone of British Columbia, Canada.
O. roddyi occurs in the Olenellus-zone of Pennsylvania.
O. romensis occurs in the middle Upper Olenellus-zone of Virginia.
O. terminatus has been collected from the final layer of the Upper Olenellus-zone of Nevada.
O. transitans has been collected from the middle Upper Olenellus-zone of Vermont.
Description
cephalon CRF.jpg|thumb|right|Olenellus chiefensis-cephalon][Image:Olenellus clarki 37mm CRF.jpeg|thumb|right|Olenellus clarki]
[Image:Olenellus nevadensis CRF.jpg|thumb|right|Olenellus nevadensis]
As with most early trilobites, Olenellus has an almost flat exoskeleton, that is only thinly calcified, and has crescent-shaped eye ridges. As part of the suborder Olenellina, Olenellus lacks dorsal sutures. Like all other members of the superfamily Olenelloide, the eye-ridges emerge from the back of the frontal lobe of the central area of the cephalon, that is called glabella. Olenellus also shares the typical character of whole family Olenellidae that the frontal and middle pair of lateral lobes of the glabella are partially merged. This creates two very typical, isolated slits. It can be distinguished from the other two genera in the family, Mesolenellus and Mesonacis, because the angle in the back rim of the cephalon is less than 15°, making the head approximately semi-circular. The genal spines are reaching back no further than the 6th thorax segment, making them 4-5 times as long as the most backward lobe of the glabella 1. The thorax is 4- times wider that the axis, measured at the 3rd segment. The base of the spine on the 15th thorax segment is almost as wide as the axis itself.