A MORPHOMETRIC STUDY OF THE EOCENE SPIDERS OF FLORISSANT, COLORADO

An outline morphometric analysis is used to make objective family placements of fossil shale spiders from the Florissant formation in Colorado using available shape characters. The carapace shape is used, as it is intact in many of the fossil spiders found. In addition, linear leg characters are used to make meaningful family placements. Multiple discriminant analysis (MDA) was used to predict family placement initially among a dataset of 202 modern spiders from eight families found in localities similar to the lake environment thought to have existed at the time of deposition. This was to determine the accuracy of the predictions made by the MDA. Our results showed that among the modern spiders, Salticidae (91.2%), Linyphiidae (80%), Dictynidae (76.5%), Tetragnathidae (68.2%), Clubionidae (66.7%), Araneidae (65.5%) were most often correctly predicted. Then forty-three fossil spiders from Florissant were added to determine their family placement. As a result of this technique, 75% of the previously described fossil spiders were removed and placed into new family combinations or were placed into Incertae sedis. This analysis is a promising example of a quantitative technique used for identifications where traditional characters are not visible.