INVERTEBRATE AND AVIAN ICHNOTAXONOMY OF THE EOCENE GREEN RIVER FORMATION, UINTA BASIN, UTAH: INTERPRETING BEHAVIORS AND LIFESTYLES, AND ERECTING THE COCHLICHNUS ICHNOFACIES

While the Eocene Green River Formation (GRF) in Uinta Basin, Utah, has a diverse ichnofauna, systematic ichnotaxonomic assessments are lacking. This is the first systematic assessment of trace fossils from Soldier Summit and Spanish Fork Canyon, Utah, localities of the GRF. We identified 19 ichnogenera and 26 ichnospecies: Acanthichnuscursorius, Alaripedalofgreni, c.f. Aquatilavipesisp., Aulichnites(A. parkerensisand A. tsouloufeidosisp. nov.), Aviadactyla(c.f. Av. isp. and Av. vialovi), Avipedaphoenix, Cochlichnus(C. anguineusand C. plegmaeidosisp. nov.), Conichnusconichnus, Fuscinapedatexana, Glaciichniumliebegastensis, Glaroseidosichnusign. nov. gierlowskiiisp. nov., Gruipeda(G. fuenzalidaeand G. gryponyx),Midorikawapedaign. nov. semipalmatusisp. nov., Planolitesmontanus, Presbyorniformipesfeduccii, Protovirgulariadichotoma,Sagittichnuslinki, Treptichnus(T. bifurcus,T. pedum, and T. vagans), and Tsalavoutichnusign. nov. (Ts.ericksoniiisp. nov. and Ts. leptomonopatiisp. nov.). Four ichnocoenoses are interpreted from the ichnofossil assemblages—Cochlichnus, Conichnus, Presbyorniformipes, and Treptichnus—representing dwelling, feeding, grazing, locomotion, predation, pupation, and resting behaviors of organisms in environments just below, at, and just above the sediment-water-air interface (SWAI). A new ichnofacies is established to represent ichnocoenoses associated with the SWAI: the Cochlichnus Ichnofacies. This ichnofacies represents the overprinting of conditions in periaquatic continental settings associated with water-margin environments with or without weak pedogenesis, which are controlled by the groundwater profile and the media. The Cochlichnus Ichnofacies can be identified in deposits from the Carboniferous (Pennsylvanian) to recent. The Cochlichnus Ichnofacies replaces the: 1) Shorebird Ichnofacies; 2) usage of the Mermia Ichnofacies for ephemeral water bodies; and 3) usage of the Scoyenia Ichnofacies for damp areas at and just above the SWAI. The Mermia Ichnofacies is restricted to trace-fossil assemblages in deeper, perennial water bodies, removing Cochlichnus, Treptichnus, and such arthropod crawling trails as Helminthoidichnites, all made in continental settings at or above the SWAI, as diagnostic traces.