Three Late Cenozoic Fish Faunas from Nebraska

Abstract

Taxonomy and paleoecology of three late Cenozoic fish faunas from Nebraska are analyzed. The Seneca fish fauna from Hooker County, and the Broadwater-Lisco fish fauna from the type localities of these formations in NIorrill and Garden counties compare closely with the Sand Draw fish fauna (Smith and Lundberg, 1972), which has been assigned a Blancan age. The Sappa fish fauna comes from the type section of the Sappa Formation in Harlan Countys and is assigned an early Pleistocene age based on faunal comparisons and a fission-track date of 1.2 + .04 m.y. (Naeser et al., 1973). The Seneca fauna contains six species in five genera and includes an osteoglossiform, Hi(vdon lirelllls, sp. nov., as well as excellent material of Lepomis serratus (Smith and Lundberg, 1972). Fish taxa from this locality represent stream, river and pond inhabitants and geological evidence for these depositional environments is present. The Broadwater-Lisco fauna contains five species in four genera and includes additional material of ktcllurus lambdu Hubbs and Hibbard. Clear, fast water may not have been present at the Broadwater-Lisco localities. The Pleistocene Sappa fish fauna contains nine species in seven genera. N(vturus spines present in this fauna cannot be identified to speciesS but represent a species in the N. (Rubizlcl) group. The Sappa site probably samples a fauna from a large cobble-bottomed stream draining silty soil. Comparison of the Sappa fauna with the Blancan faunas discussed earlier indicates that three species are morphologically similar in Blancan and Pleistocene deposits. 55% of the species discussed in this work are now extinct Interpretation of the paleoenvironment at all localities is enhanced by simultaneous study of the sequence and nature of primary sedimentary xtructures and of the ichthyofauna living in these depositional environments.