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''Olenellus'' is an
extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
of redlichiid
trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the ...
s, with species of average size (about long). It lived during the
Botomian Cambrian Stage 4 is the still unnamed fourth stage of the Cambrian and the upper stage of Cambrian Series 2. It follows Cambrian Stage 3 and lies below the Wuliuan. The lower boundary has not been formally defined by the International Commission on ...
and
Toyonian Cambrian Stage 4 is the still unnamed fourth stage of the Cambrian and the upper stage of Cambrian Series 2. It follows Cambrian Stage 3 and lies below the Wuliuan. The lower boundary has not been formally defined by the International Commission ...
stages (''Olenellus''-zone), , in what is currently North-America, part of the palaeocontinent
Laurentia Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, althoug ...
.


Etymology

''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 Myth is a folklore genre consisting of narratives that play a fundamental role in a society, such as foundational tales or origin myths. Since "myth" is widely used to imply that a story is not objectively true, the identification of a narrati ...
who was turned to stone by the gods. The names of the species have the following derivations. * ''agellus'' comes from the
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
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 afte
Noah L. Getz
on whose Lancaster estate several ''Olenellus'' species were first collected. * ''nevadensis'' refers to the state of
Nevada Nevada ( ; ) is a U.S. state, state in the Western United States, Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. N ...
, 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 (1856-1943), 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''.


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 (Paedeumias)'' nested within ''Olenellus'' (''O. clarki'', ''O. nevadensis'', ''O. parvofrontatus'', ''O. roddyi'' and ''O. transitans''). 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 In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gr ...
subgenera need to be erected, or ''Olenellus (Paedeumias)'' and ''Olenellus (Olenellus)'' need to be dropped as subgenera, the latter being proposed by Lieberman.


Reassigned species

* ''O. alabamensis'' = '' Fremontella halli'' * ''O. altifrontatus'' = '' Bolbolenellus altifrontatus'' * ''O. argentus'' pl. 40, fig 12, 13, 15, 16, non fig. 14 = ''Grandinasus argentus'' * ''O. argentus'' pl. 40, fig 14, non fig. 12, 13, 15, 16 = ''Holmiella falx'' * ''O. bondoni'' = '' Fallotaspis bondoni'' * ''O. bonnensis'' = '' Mesonacis bonnensis'' * ''O. brevoculus'' = '' Mesonacis bonnensis'' * ''O. broegeri'' = '' Callavia broegeri'' * ''O. bristolensis'' = '' Bristolia bristolensis'' * ''O. bristolensis'' p. 8. fig 1-11, non pl. 7, fig 1, 2, 5 = '' Bristolia harringtoni'' * ''O. bufrontis'' = '' Bolbolenellus sphaerulosus'' * ''O. callavei'' = ''Callavonia callavei'' * ''O. cylindricus'' = '' Mesonacis cylindricus'' * ''O. eagerensis'' = '' Mesonacis eagerensis'' * ''O. euryparia'' = '' Bolbolenellus euryparia'' * ''O. forresti'' = '' Redlichia forresti'' * ''O. fremonti'' pl. 15, fig. 18 = '' Bristolia fragilis'' * ''O. fremonti'' pl. 37, fig. 1, 4-5 = '' Bolbolenellus euryparia'' * ''O. fremonti'' pl. 37, fig. 1-2 = '' Mesonacis fremonti'' * ''O. georgiensis'', p. 220, pl. 5, fig. 7, non fig. 6 = '' Mesonacis vermontanus'' * ''O. gigas'' = ''Andalusiana cornuta'' * ''O. gilberti'' = '' Bristolia bristolensis'' * ''O. groenlandicus'' = '' Bolbolenellus groenlandicus'' * ''O. halli'' = '' Fremontella halli'' * ''O. hamoculus'' = '' Mesonacis hamoculus'' * ''O. hermani'' = '' Bolbolenellus hermani'' * ''O. hyperboreus'' = '' Mesolenellus hyperboreus'' * ''O. insolens'' = '' Bristolia insolens'' * ''O. intermedius'' = '' Fritzolenellus lapworthi'' or ''F. reticulatus'' * ''O. kentensis'' = '' Bolbolenellus groenlandicus'' * ''O. lapworthi'' = '' Fritzolenellus lapworthi'' * ''O. laxocules'' = '' Elliptocephala laxocules'' * ''O. logani'' = '' Elliptocephala logani'' * ''O. mickwitzi'' = '' Schmidtiellus mickwitzi mickwitzi'' * ''O. mohavensis'' = '' Bristolia mohavensis'' * ''O. multinodus'' = '' Nephrolenellus multinodus'' * ''O. paraocules'' = '' Elliptocephala paraocules'' * ''O. praenuntius'' = '' Elliptocephala praenuntius'' * ''O. reticulatus'' = '' Fritzolenellus reticulatus'' * ''O. sequomalus'' = '' Elliptocephala sequomalus'' * ''O. sphaerulosus'' = '' Bolbolenellus sphaerulosus'' * ''O. svalbardensis'' = '' Mesolenellus svalbardensis'' * ''O. terranovicus'' = '' Mesonacis bonnensis'' * ''O. torelli'' = '' Schmidtiellus mickwitzi torelli'' * ''O. truemani'' = '' Elliptocephala walcotti'' * ''O. truemani'' = '' Fritzolenellus truemani'' * ''O. truncatooculatus'' = '' Mummaspis truncatooculatus'' * ''O. vermontanus'' = '' Mesonacis vermontanus'' * ''O. walcottanus'' = '' Wanneria walcottana''


Distribution

''O. thompsoni '' is found in the middle Upper ''Olenellus''-zone of Vermont ( Franklin County, Parker Slate, Georgia). ''O. agellus'' is present in the middle Upper ''Olenellus''-zone of Vermont (Parker Slate, Georgia). ''O. chiefensis'' has been collected from the final layer of the Upper ''Olenellus''-zone of Nevada ( Pioche Formation). ''O. clarki'' is found in Upper ''Olenellus''-zone of California (Bristol Mountain, near Cadiz, on the Santa Fé Railroad, 100 miles East of Barstow, Mohave Desert, probably Latham Shale; Latham Shale – treated as the ''Bristolia''-zonule – Marble Mountains, ½ mile East of Cadiz, and at the Southern end of the Marble Mountains, near Chambless in the Mohave Desert portion of
San Bernardino County San Bernardino County (), officially the County of San Bernardino, is a county located in the southern portion of the U.S. state of California, and is located within the Inland Empire area. As of the 2020 U.S. Census, the population was 2,181, ...
, as well as from the Latham Shale, near Summit Springs on the West side of the Providence Mountains, San Bernardino County. In California also from the Carrara Formation, Funeral Mountains,
Resting Spring Range The Resting Spring Range is found in the eastern Mojave Desert of California near the Nevada state line in the United States. The range lies in a generally north–south direction to the west of the Nopah Range and southeast of the Amargosa Rang ...
, Eagle mountain, Grapevine Mountains, Salt Spring Hills); and in Nevada (
Nevada Test Site The Nevada National Security Site (N2S2 or NNSS), known as the Nevada Test Site (NTS) until 2010, is a United States Department of Energy (DOE) reservation located in southeastern Nye County, Nevada, about 65 miles (105 km) northwest of the ...
, Desert Range). ''O. crassimarginatus'' has been collected in the middle Upper ''Olenellus''-zone of Vermont (Parkers Quarry, Parker Slate, Georgia); and ½ mile South of East Petersburg; 2 miles North of York and Fruitville, 3 miles North of Lancaster (all in the Kinzers Shale). ''O. fowleri'' has been collected from the final layer of the Upper ''Olenellus''-zone of Nevada (Pioche Formation). ''O. getzi'' is found in Upper ''Olenellus''-zone of Pennsylvania (2 miles North of York, and Noah Getz Farm, 1 mile North of Rohrerstown, Kinzers Shale). ''O. howelli'' occurs in the final layer of the Upper ''Olenellus''-zone of Nevada (Pioche Formation). ''O. nevadensis'' has been collected in the Upper ''Olenellus''-zone, ''Bristolia''-zonule of California (Carrara Formation, Funeral Mountains and Grapevine Mountains); 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 (Carrara Formation, Desert Range, Locality M-5). ''O. parvifrontatus'' has been collected in the ''Olenellus''-zone of the Yukon Territory, Canada (Unit 6 of the Upper Illtyd Formation, Wernecke Mountains). ''O. puertoblancoensis'' was found in the Botonian/Toyonian ''Olenellus''-zone of the Caborca Region, Mexico (Buelna Formation, Cerro Rajon) ''O. robsonensis'' occurs in the ?Middle ''Olenellus''-zone of British Columbia, Canada (?Upper Mahto Formation, drift block on the slope of the Mural Glacier below Mumm Peak, Near Mount Robson). ''O. roddyi'' occurs in the ''Olenellus''-zone of Pennsylvania (2 miles North of York, Fruitville; 3 miles North of Lancaster; Getz Quarry; 1 mile North of Rohrerstown; ½ mile South of East Petersburg; all in the Kinzers Shale). ''O. romensis'' occurs in the middle Upper ''Olenellus''-zone of Virginia (Rome Formation, Mason Creek, Salem; North-East of Roanoke, near Webster; 2 miles South-West of Blue Ridge Springs, 2 miles South of Max Meadows; Mason Creek, 1 mile east of Salem; ½ mile South-East of Indian Rock; 1 mile East of Cleveland, Alabama; 1½ miles North of Montevallo; 1½ miles West of Montevallo). ''O. terminatus'' has been collected from the final layer of the Upper ''Olenellus''-zone of Nevada (Pioche Formation). ''O. transitans'' has been collected from the middle Upper ''Olenellus''-zone of Vermont (Parker Slate, Georgia).


Description

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 (L4) of the central area of the
cephalon Cephalon, Inc. was an American biopharmaceutical company co-founded in 1987 by pharmacologist Frank Baldino, Jr., neuroscientist Michael Lewis, and organic chemist James C. Kauer—all three former scientists with the DuPont Company. Baldino s ...
, that is called
glabella The glabella, in humans, is the area of skin between the eyebrows and above the nose. The term also refers to the underlying bone that is slightly depressed, and joins the two brow ridges. It is a cephalometric landmark that is just superior t ...
. ''Olenellus'' also shares the typical character of whole family Olenellidae that the frontal (L3) and middle pair (L2) 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 (occipital ring or L0)1. The
thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the c ...
is 4-4½ 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.


Key to the species

This key is based on Lieberman (1999), which describes only part of the species that are recognized today.


References


External links


photograph of ''Olenellus chiefensis''

photograph of ''Olenellus getzi''

photograph of ''Olenellus gilberti''



photograph of ''Olenellus thompsoni''

photograph of ''Olenellus transitans''
{{Taxonbar, from=Q26270 Olenellidae Redlichiida genera Cambrian trilobites Index fossils Fossils of Canada Fossils of Mexico Fossils of the United States Paleozoic life of Alberta Paleozoic life of British Columbia Paleozoic life of Newfoundland and Labrador Paleozoic life of Nunavut Taxa named by Elkanah Billings Cambrian genus extinctions