TOADSTOOL PARK VERTEBRATE TRACKWAYS (OLIGOCENE, BRULE FORMATION, NORTHWESTERN NEBRASKA): ICHNOLOGICAL STUDY ENHANCED THROUGH DIGITAL REPRODUCTION

Vertebrate tracks and trackways representing a diversity of track makers are preserved at Toadstool Geological Park in northwestern Nebraska. The ichnofossils are preserved at the top of a sheet sandstone in the Orella Member of the Brule Formation (White River Group, Oligocene). We interpret the best preserved tracks as those of the medium size rhinoceros Subhyracodon. Tracks of other members of the White River body fossil fauna are also recognized, including Mesohippus, entelodonts, oreodonts, birds and invertebrates. Three-dimensional photogrammetric documentation is being used facilitate ichnological and paleoecological study of the trackways, as large trackways like this one are vulnerable to rapid destruction by weathering, foot traffic and vandalism but nearly impossible to collect. Photogrammetric products like millimeter-resolution digital terrain models provide accurate reproduction of details, are easier to manipulate than both the original tracks in the outcrop and molds or casts made from them and they can be distributed widely to multiple researchers. Methods adapted from remote sensing and geographic information systems to the analysis of digital trackway data can be used to quantify track geometry and enhance visual observation of ichnological information.