A TAXONOMIC STUDY OF THE EOCENE SPIDERS FROM FLORISSANT, COLORADO

The 34.1 million year old Florissant formation in central Colorado holds some of the most beautifully preserved and unique fossils from the Tertiary. This well known deposit is rich with fossil plants, vertebrates, and arthropods, which have been studied for over one hundred years. The order of spiders, Araneae, is among the most diverse groups on earth and is abundant with more than 150 specimens from the Florissant formation. It is believed that this order originated in the Devonian, with a major radiation in the early Mesozoic and many of the modern families have origins well into the Late Cretaceous. Generally, fossil deposits containing spiders are rare, however, the record from the Tertiary is robust based on amber deposits in Europe and the Dominican Republic and fossil shale deposits like Florissant. As a result, Florissant is internationally renowned for its rare and excellently preserved spider fossils. Two previous researchers, Samuel Scudder in the late nineteenth century and Alexander Petrunkevitch in the early twentieth century, had researched the Florissant spider assemblage. Both identified these specimens to the species level. When looking at modern spiders, many generic and all specific designations are based on genitalic characters. Although the fossils are exquisitely preserved, this important character is not clearly visible in any of the specimens. I have evaluated 72 of the 77 total type spiders described by Scudder and Petrunkevitch. The characters used to evaluate these spiders to family level are carapace shape, abdomen shape, chelicerae size, and leg length. Of the 72 type specimens evaluated, I have reassigned 54 into different families and maintained the family placement of the remaining 18 spiders. However, 3 spiders that have stayed in the same family have questionable affinities