02085nas a2200217 4500008004100000245013600041210006900177300001400246490000700260520131700267653001701584653002201601653001801623653004201641653003101683100001901714700002001733700001801753700001601771856008001787 2014 eng d00aTrilobite Biostratigraphy of the Stairsian Stage (upper Tremadocian) of the Ibexian Series, Lower Ordovician, Western United States0 aTrilobite Biostratigraphy of the Stairsian Stage upper Tremadoci a167–2140 v453 a

New field collections from sections in western Utah and southeastern Idaho permit the development of a high resolution trilobite biostratigraphy for the northern Laurentian Lower Ordovician (upper Tremadocian) Stairsian Stage similar to that proposed previously for the overlying Tulean and Blackhillsian stages. Four zones recognised previously are replaced with 11 formally proposed zones, most of which are new in concept. The new zonal scheme in ascending order includes the 'Paraplethopeltis genacurva' Zone (replaces 'Paraplethopeltis Zone'/'Zone C'), 'Paraplethopeltis helli' Zone (new), 'Hystricurus zanderi' Zone (new), 'Rossaspis leboni' Zone (new), Unnamed Zone 1 (new), 'Bearriverops loganensis' Zone (new; contains much of the diversity previously assigned to 'Tesselacauda Zone'/'Zone E'), 'Bearriverops deltaensis' Zone (new), 'Bearriverops alsacharovi' Zone (new), 'Pseudoclelandia weymouthae' Zone (new), 'Pseudoclelandia cornupsittaca' Zone (new) and 'Pseudohystricurus obesus' Zone (new). The latter two zones were previously lumped as the 'Rossaspis superciliosa Zone'/'Zone F'. Four of the name bearers of the new zones, 'Paraplethopeltis helli' sp. nov., 'Hystricurus zanderi' sp. nov., 'Rossaspis leboni' sp. nov. and 'Pseudoclelandia weymouthae' sp. nov., are formally described.

10apaleontology10aSpecies diversity10aStratigraphic10aTrilobites--Collectors and collecting10aTrilobites--Type specimens1 aAdrain, J., M.1 aWestrop, S., R.1 aKarin, T., S.1 aLanding, E. uhttp://search.informit.com.au/documentSummary;dn=343657705520848;res=IELHSS01843nas a2200181 4500008004100000245016400041210006900205300001100274490000700285520114300292653002501435100001901460700001601479700002001495700002601515700001601541856010401557 2003 eng d00aClassification of the Trilobite Subfamilies Hystricurinae and Hintzecurinae subfam. nov., with New Genera from the Lower Ordovician (Ibexian) of Idaho and Utah0 aClassification of the Trilobite Subfamilies Hystricurinae and Hi a55-1050 v413 a

The Hystricuridae, previously regarded by most workers as a paraphyletic group, is considered on the basis of new and revised silicified species from Utah and Nevada. Major subgroups of hystricurids appear to be monophyletic, but the sister group relationships of several related families require investigation. The Hystricurinae is restricted to Hystricurus Raymond, 1913, Tersella Petrunina, 1973, and Flectihystricurus gen. nov. (type species: Hystricurus flectimembrus Ross, 1951). A new subfamily Hintzecurinae is diagnosed. The subfamily appears to be restricted to the upper Skullrockian Stage, and comprises the new genera Hintzecurus (t.s.: Hystricurus paragenalatus Ross, 1951), Genalaticurus (t.s.:Hystricurus genalatus Ross, 1951), Ibexicurus (t.s.: I. parsonsi sp. nov.), Lavadamia (t.s.: L.joplinae sp. nov.), Politicurus (t.s.: Hystricurus politus Ross, 1951), and Rossicurus (t.s.:Hystricurus lepidus Hintze, 1953). _ Trilobites, Hystricuridae, Ordovician, Idaho, Utah.

10ageology paleontology1 aAdrain, J., M.1 aLee, D., C.1 aWestrop, S., R.1 aChatterton, B., D. E.1 aLanding, E. uhttps://nysm.nysed.gov/staff-publications/classification-trilobite-subfamilies-hystricurinae-and-hi01845nas a2200205 4500008004100000245013000041210006900171300001200240490000700252520119600259653001701455653002101472653001501493653001701508100001901525700002001544700001601564700001901580856004001599 2001 eng d00aSystematics of the Ordovician Trilobites Ischyrotoma and Dimeropygiella, With Species from the Type Ibexian Area, Western USA0 aSystematics of the Ordovician Trilobites Ischyrotoma and Dimerop a947-9710 v753 a

Lower Ordovician sections in the type Ibexian area of western Utah contain a considerably more diverse trilobite fauna than has previously been reported. Reinvestigation of these faunas, based on new field sampling, allows a reassessment of the dimeropygid genera Ischyrotoma Raymond, 1925, and Dimeropygiella Ross, 1951. These taxa have been considered synonyms, but parsimony analysis indicates each is a well supported clade, and they are best recognized as sister genera. The number of species known from Ibex has been doubled, from four to eight, and morphological information is now available for most parts of the exoskeleton. New species include Ischyrotoma juabensis (Juab Formation), I. wahwahensis (Wah Wah Formation), Dimeropygiella fillmorensis (Fillmore Formation), and D. mccormicki (Fillmore Formation). The previously named species Dimeropygiella caudanodosa, D. blanda, and D. ovata are fully revised on the basis of abundant new material. Pseudohystricurus is a paraphyletic group, with species distributed as a basal grade of the Ischyrotoma/Dimeropygiella group.

10aIbexian area10aLower Ordovician10atrilobites10awestern Utah1 aAdrain, J., M.1 aWestrop, S., R.1 aLanding, E.1 aFortey, R., A. uhttp://www.jstor.org/stable/1307060