Abstract
The previously monotypic bathyurid trilobite Aponileus Hu, 1963, was known only from poorly preserved material of itstype species, A. latus, and was interpreted as a junior subjective synonym of Psephosthenaspis Whittington. New speciesfrom the upper Floian (Blackhillsian) Fillmore Formation of western Utah belong to Aponileus and help demonstrate thatthe genus is an entirely Lower Ordovician (upper Floian) clade phylogenetically separate from the Middle Ordovician(Dapingian) Psephosthenaspis. Species of either group have broadly similar morphology, but the species of Psephosthe-naspis which most closely resembles those of Aponileus is the youngest and most derived member, and the similarities areconvergent. Psephosthenaspis roots among a group of heavily tuberculate, mostly undescribed, upper Floian species, oneof which is briefly illustrated for comparison. The species most resembling some species of Aponileus, P. glabrior, is il-lustrated on the basis of new silicified material which extends its range from the upper Juab Formation into the base of theKanosh Formation. New Blackhillsian species are A. laikaae (Fillmore Formation; Presbynileus ibexensis Zone), A. aasei(Fillmore Formation; probably Pseudocybele paranasuta Zone), A. belkaae, A. strelkaae, and A. ugolekae (all Wah WahFormation; "Pseudocybele nasuta Zone"). Aponileus? veterokae n. sp., from high in the "Pseudocybele nasuta Zone" ofthe Wah Wah Formation, is tentatively assigned. Bolbocephalus glaber Poulsen, 1927, from the Nunatami Formation ofnorthwest Greenland, is poorly known but is also a member of Aponileus, and is similar in morphology to A. latus and A.aasei; it is revised on the basis of reillustrated type material. Phylogenetic analysis indicates that A. laikaae is the basalspecies, followed by a sister pair of A. belkaae and A. strelkaae. These are sister to a pair of subclades, the sister pair of A. ugolekae and A.? veterokae, and an effaced group lacking genal spines including A. aasei, A. latus, and A. glaber.References
Adrain, J.M. & Westrop, S.R. (2005) Lower Ordovician trilobites from the Baumann Fiord Formation, Ellesmere Island, Arctic Canada. Canadian Journal of Earth Sciences, 42, 1523–1546.
Adrain, J.M., McAdams, N.E.B. & Westrop, S.R. (2009) Trilobite biostratigraphy and revised bases of the Tulean and Blackhillsian Stages of the Ibexian Series, Lower Ordovician, western United States. Memoirs of the Association of Australasian Palaeontologists, 37, 541–610.
Adrain, J.M., McAdams, N.E.B. & Westrop, S.R. (In press) Systematics and affinity of the Lower Ordovician (Tulean; lower Floian) trilobite Psalikilopsis. Memoirs of the Association of Australasian Palaeontologists.
Adrain, J.M., McAdams, N.E.B. & Westrop, S.R. (In review) Affinities of the Lower Ordovician (Tulean; lower Floian) trilobite Gladiatoria, with species from the Great Basin, western United States. Memoirs of the Association of Australasian Palaeontologists.
Billings, E. (1859) Fossils of the Calciferous Sandrock, including those of a deposit of white limestone at Mingan, supposed to belong to the formation. Canadian Naturalist and Geologist, 4, 345–367.
Billings, E. (1865) Palaeozoic fossils. Vol. I (4). Geological Survey of Canada, Montreal, pp. 169–344.
Boyce, W.D., Knight, I., Rohr, D.M., Williams, S.H. & Measures, E.A. (2000) The upper St. George Group, western Port au Port Peninsula: Lithostratigraphy, biostratigraphy, depositional environments and regional implications. 2000-1, 101–125.
Brett, K.D. & Westrop, S.R. (1996) Trilobites of the Lower Ordovician (Ibexian) Fort Cassin Formation, Champlain Valley regions, New York State and Vermont. Journal of Paleontology, 70, 408–427.
Derby, J.R. (1975) Lower Ordovician-Middle Ordovician boundary in western Arbuckle Mountains, Oklahoma. In: Ham, W.E. (Ed.), Regional Geology of the Arbuckle Mountains, Oklahoma. Guidebook for Field Trip No. 5, November 10-11, 1973. Oklahoma Geological Survey, The University of Oklahoma, Norman, Oklahoma, pp. 24–26.
Fortey, R.A. & Bruton, D.L. (1973) Cambrian-Ordovician rocks adjacent to Hinlopenstretet, North Ny Friesland, Spitsbergen. Geological Society of America Bulletin, 84, 2227–2242.
Fortey, R.A. & Droser, M.L. (1996) Trilobites at the base of the Middle Ordovician, western United States. Journal of Paleontology, 70, 73–99.
Goloboff, P.A., Farris, J.S., Källersjö, M., Oxelman, B., Ramírez, M.J. & Szumik, C.A. (2003) Improvements to resampling measures of group support. Cladistics, 19, 324–332.
Hintze, L.F. (1951) Lower Ordovician detailed stratigraphic sections for western Utah. Utah Geological and Mineralogical Survey Bulletin, 39, 1–99.
Hintze, L.F. (1953) Lower Ordovician trilobites from western Utah and eastern Nevada. Utah Geological and Mineralogical Survey Bulletin, 48, 1–249. (for 1952)
Hintze, L.F. (1973) Lower and Middle Ordovician stratigraphic sections in the Ibex area, Millard County, Utah. Brigham Young University Geology Studies, 20, 3–36.
Hu, C.-H. (1963) Some Lower Ordovician trilobites from Franklin Mountains, Texas. Transactions and Proceedings of the Palaeontological Society of Japan, N.S. 51, 86–90.
Hughes, C.P. (1979) The Ordovician trilobite faunas of the Builth-Llandrindod Inlier, central Wales. Part III. Bulletin of the British Museum (Natural History), Geology Series, 32, 109–181.
Hupé, P. (1955) Classification des Trilobites. Annales de Paléontologie, 41, 111–345.
Jell, P.A. & Adrain, J.M. (2003) Available generic names for trilobites. Memoirs of the Queensland Museum, 48, 331–553.
Lochman-Balk, C. & Wilson, J.L. (1967) Stratigraphy of Upper Cambrian-Lower Ordovician subsurface sequence in Williston Basin. The American Association of Petroleum Geologists Bulletin, 51, 883–917.
McAdams, N.E.B. & Adrain, J.M. (2007) Phylogenetics of the Ordovician Acidiphorus-group bathyurid trilobites. Geological Society of America Abstracts with Programs, 39(6), 499.
McAdams, N.E.B. & Adrain, J.M. (2010) A new species of the Lower Ordovician pliomerid trilobite Pseudocybele and its biostratigraphic significance. Zootaxa, 2550, 21–38.
Poulsen, C. (1927) The Cambrian, Ozarkian and Canadian faunas of northwest Greenland. Meddelelser om Grønland, 70, 235–343.
Poulsen, C. (1946) Notes on Cambro-Ordovician fossils collected by the Oxford University Ellesmere Land Expedition 1934-5. Quarterly Journal of the Geological Society of London, 102, 299–337.
Raymond, P.E. (1910) Notes on Ordovician trilobites, II. Asaphidae from the Beekmantown. Annals of the Carnegie Museum, 7, 35–44.
Raymond, P.E. (1925) Some trilobites of the lower Middle Ordovician of eastern North America. Bulletin of the Museum of Comparative Zoology, Harvard University, 67, 1–180.
Ross, R.J., Jr. (1949) Stratigraphy and trilobite faunal zones of the Garden City Formation, northeastern Utah. American Journal of Science, 247, 472–491.
Ross, R.J., Jr. (1951) Stratigraphy of the Garden City Formation in northeastern Utah, and its trilobite faunas. Peabody Museum of Natural History, Yale University, Bulletin, 6, 1–161.
Ross, R.J., Jr. (1953) Additional Garden City (Early Ordovician) trilobites. Journal of Paleontology, 27, 633–646.
Ross, R.J., Jr. (1967) Some Middle Ordovician brachiopods and trilobites from the Basin Ranges, western United States. United States Geological Survey Professional Paper, 523-D, 1–43.
Ross, R.J., Jr. (1970) Ordovician brachiopods, trilobites, and stratigraphy in eastern and central Nevada. United States Geological Survey Professional Paper, 639, 1–103.
Tremblay, J.V. & Westrop, S.R. (1991) Middle Ordovician (Whiterockian) trilobites from the Sunblood Formation, District of Mackenzie, Canada. Journal of Paleontology, 65, 801–824.
Ulrich, E.O. (1927) Fossiliferous boulders in the Ouachita “Caney” shale and the age of the shale containing them. Oklahoma Geological Survey Bulletin, 45, 1–48.
Walcott, C.D. (1886) Second contribution to the studies on the Cambrian faunas of North America. United States Geological Survey Bulletin, 30, 1–369.
Whittington, H.B. (1948) A new Lower Ordovician trilobite. Journal of Paleontology, 22, 567–572.
Whittington, H.B. (1953) North American Bathyuridae and Leiostegiidae (Trilobita). Journal of Paleontology, 27, 647–678.
Young, G.E. (1973) An Ordovician (Arenigian) trilobite faunule of great diversity from the Ibex area, western Utah. Brigham Young University Geology Studies, 20, 91–115.