| Upper Marjuman trilobites from the eastern Great Basin area (western Utah and eastern Nevada) are documented in this study. Eight families, four subfamilies, twenty genera, and fifty-seven species were identified. Thirty-one of them are new species. They are described and illustrated here: Crepicephalus charliebrowni, C. schroederi, C. sallybrownae, C. spikei, C. snoopyi, C. woodstocki, C. lucyvanpeltae, C. linusvanpelti, C. rerunvanpelti, Coosella paraperplexa, C. magna, C. lata, C. quadrata, C. orbis, C. trapezia, Coosia macro, Blountia palmeri, B. lincolnensis, B. millardensis, Kingstonia greatbasinensis, K. bighorsensis, Komaspidella emigrantspringsensis, Llanoaspis houserangensis, Tricrepicephalus beethoveni, T. brahmsi, T. schumanni, Meteoraspis rasettii, M. robisoni, M. walcotti, Cheilocephalus pattersonensis, and Aphelaspis hui. Most of these species are endemic and only exist in the Great Basin area.;A new biostratigraphic scheme for the study area, includes, in ascending order, the Kingstonia great basinensis-Coosina ariston Zone, Tricrepicephalus beethoveni-Meteoraspis walcotti Zone, Coosella paraperplexa Zone and Aphelaspis hui Zone. The new scheme can enhance the resolution of this area, and the C. paraperplexa Zone is correlative with the C. perplexa Subzone in Texas.;Distinctive Crepicephalus, Coosella paraperplexa and Aphelaspis faunas illustrate a pre-extinction, transitional and post-extinction pattern. Six biofacies can be interpreted by using two-way Q- and R-mode cluster analysis. But both non-metric multidimensional scaling (NMS) and detrended correspondence analysis (DCA) show weak support for this pattern.;A first attempt at cladistic analysis of the genera Coosia, Coosella, Coosina, Crepicephalus, Meteoraspis, and Tricrepicephalus is presented. Robust result shows that Meteoraspis, and Tricrepicephalus are sister taxa and monophyletic. Coosella and Coosia are also monophyletic but with weak character support. Coosina and Crepicephalus are paraphyletic according to this analysis. However, further investigation with broader taxon sampling is needed to further test these preliminary results. |
