FOSSIL TERRESTRIAL ARTHROPODS OF THE '7-11 MINE' (DESMOINESIAN-MISSOURIAN: PENNSYLVANIAN: CARBONIFEROUS), COLUMBIANA COUNTY, EASTERN OHIO

Terrestrial arthropods from two horizons dominate (377 specimens or 71% abundance) the fossil fauna of the 7-11 Mine examined in a recent census. The lower fossil horizon (Missourian) is confined within a paleochannel unconformably overlying the Upper Freeport Coal and underlying a thin coal questionably referred to the "Mason Coal." The lower horizon includes the trigonotarbid arachnid Pleophrynus verrucosa and the millepded Xyloiulus preserved in iron-rich claystone. The upper horizon (Missourian) overlies the "Mason Coal" and underlies the recently recognized Rock Camp marine zone. The upper horizon is dominated by blattoids (cockroaches) (351 specimens), including the largest known Paleozoic blattoid, but also includes a juvenile xiphosuran Bellinurus, the trigonotarbid arachnids P. verrucosa and Aphantomartus pustulatus, the giant myriapod Arthropleura cristata, the millepede Xyloiulus, a new genus and species of gerarid insect, and fragments of an unknown insect wing preserved as carbonized compressions in dark shale with siderite concretions. The Bellinurus specimen represents one of the youngest occurrences of the genus in the fossil record. The Aphantomartus represents only the second occurrence of the genus in North America besides Mazon Creek, Illinois (Desmoinesian). The Arthropleura represents only the sixth occurrence of the genus in North America. Most terrestrial arthropods are preserved as disarticulated fragments (primarily blattoid wings); however, partially articulated and fully articulated specimens do rarely occur, including the large blattoid, A. pustulatus, and Xyloiulus. Some blattoid wings show evidence of heterogeneous thicknesses, possibly representing coloration patterns.