Fauna and Depositional Environment of a Late Pennsylvanian Vertebrate Fossil Locality in Southeastern Kansas

Abstract

A vertebrate fossil locality in Greenwood County, Kansas, near the town of Toronto, in the Snyderville (Shale) member of the Oread (Limestone) Formation (Late Pennsylvanian, Virgilian) contains an abundance of disarticulated fossils weathering out of a paleosol. This new locality is stratigraphically between the previously-described Late Pennsylvanian Hamilton (Virgilian) and Garnett (Missourian) fossil localities, thus helping to fill the temporal gap between these two. The paleosol contains 11 paleohorizons of alternating grey and red clays capped by thin weathered sandstone blocks with micro-crossbedding, which is consistent with channel sand deposits. Over 2000 fossils were collected, all of which were disarticulated, complicating identification. Identified taxa include the xenacanth shark Orthacanthus, the lungfish Sagenodus c.f. S. Serratus, the temnospondyl amphibians, embolomerous and diadectid reptiliomorphs, and synapsid amniotes. So far, no fossil invertebrates or plants have been discovered. The fossil fish and the amphibians indicate the nearby presence of fresh water. This, together with the presence of the weathered sandstone blocks, suggests that the depositional environment was a fluvial floodplain. The remains were probably first disarticulated within the stream, and then the smaller bones, teeth, and spines were sorted while in the stream and/or during a flood event. They could then have been deposited in a depression in the landscape, such as a swale. The Toronto locality has faunal similarities to both the Hamilton Quarry and Garnett fossil localities. However, unlike both of these other localities, which have articulated specimens, this locality only has disarticulated specimens. Additionally, while the other two localities also each has invertebrates and flora, the Toronto locality has only vertebrates. The Garnett locality was an estuarine setting, whereas the Hamilton Quarry fossils were all deposited within a fluvial channel, and the Toronto locality was a floodplain that shows no direct marine influence