POTENTIAL MICROSCALE PRESERVATION IN MAZON CREEK’S “DASYLEPTUS” SP

“Dasyleptus” sp., is a fossil apterygote insect of the order Archaeognatha from the Mazon Creek fossil beds in northern Illinois. The Mazon Creek specimens were described as a member of the genus Dasyleptus by Kukalová-Peck in 1987, but no species names have been given, and even the placement within Dasyleptus has since been called into question. Recent work with modern Archaeognatha has found that ovipositor setation can provide taxonomically useful information. Here we use scanning electron microscopy (SEM) to investigate the microscale preservation of three specimens of Mazon Creek “Dasyleptus” sp. from The David and Sandra Douglass Collection. Preliminary results of these investigations provide evidence of fine-scale preservation of various features. First, the ovipositors of three specimens show both internal and external preservation of segmentation. So far, specific ovipositor setation has yet to be found; however, taphonomic variability is high in Mazon Creek fossils, and additional analyses of more specimens may reveal preserved setation. Second, we observed small ~10µm, regularly spaced holes on the surface of one specimen, which we interpret as the attachment points of scales. Similar holes cover the exoskeletons of modern relatives of “Dasyleptus.” This provides the first evidence of scales in Mazon Creek “Dasyleptus.” Our results show that preservation of micro-scale structures does occur in “Dasyleptus” sp., and additional study of these features may help untangle the taxonomy of the enigmatic Mazon Creek specimens assigned to this group. Moreover, this suggests that similar microscale features may preserve in other Mazon Creek arthropods, and that more extensive SEM analysis of these fossils could be helpful in future work.