FOSSIL SPIDERS IN PALEOGENE LACUSTRINE DEPOSITS

Fossil spiders are relatively rare, and are usually found preserved in amber or lacustrine deposits. Spiders are typically preserved in lacustrine deposits as compression fossils, molds, and impressions. The fossil spiders of several Paleogene lacustrine deposits are in need of reexamination and taxonomic revision. The Green River and Florissant formations of Colorado (Eocene), the Kishenehn formation of Montana (Eocene), and Aix-en Provence of France (Oligocene), have a relative abundance of fossil spiders with most descriptions dating from the late 1800s to early 1900s or no formally described specimens. Although there is a relative abundance of fossil spiders from the Green River Formation, the only spiders formally described include the families Linyphiidae, Uloboridae, Thomisidae, Hersiliidae, and Selenopidae. The Florissant Formation spiders were originally described by Scudder (1890) and then later revisited by Petrunkevitch (1922) and include the families Araneidae, Linyphiidae, Lycosidae, Tetragnathidae, and others. Fossil spiders from Kishenehn remain undescribed, but resemble araneoids and lycosoids. Spiders from Aix-en Provence are preserved as molds/impressions in gypsum marl and include many unreliable identifications by Gourret (1887). Most spiders in the Aix Formation appear to be lycosoids and araneoids. Here, the fossils are revisited or newly described to gain a more accurate view of spider diversity surrounding lacustrine environments during the Paleogene.