EVIDENCE FOR SILK-SPINNING IN TRIGONOTARBID ARACHNIDS (CHELICERATA: TETRAPULMONATA) AND OTHER NEW DISCOVERIES FROM CEMETERY HILL (CARBONIFEROUS: DESMOINESIAN-MISSOURIAN), COLUMBIANA COUNTY, EASTERN OHIO

New structures (‘microtubercle rows’) are reported on the patella and tibia of the fourth walking legs of the trigonotarbid Aphantomartus pustulatus. These ‘rows’ are similar in shape and location to the calamistrum (used to comb out fine catching threads) in cribellate spiders. Silk-producing structures are unknown in trigonotarbids. Alternatively, these ‘microtubercle rows’ may represent cleaning structures or possibly trichobothria, filiform hairs of extreme sensitivity used to trigger ‘fight or flight’ responses in spiders. Numbers of trichobothria are known to correspond to spider ecology—with 20 to 1000 per leg of ground spiders and about 10 per leg of web spiders. Thirty-seven microtubercles are reported on the ‘row’ of the left patella on the Cemetery Hill Aphantomartus, which is consistent with ground spiders and the interpretation that Aphantomartus was a ‘sit-and-wait’ predator.

Microtubercles (tiny tubercles of unknown function(s)) have only previously been reported on Aphantomartus opisthosoma surrounding larger pustules or on fragments. The Cemetery Hill Aphantomartus further demonstrates microtubercle distribution on the prosoma and areas surrounding junctures of opisthosomal tergites, suggesting a mechanoreceptor function for these microtubercles (as with tactile hairs in modern spiders).

Other new discoveries at Cemetery Hill (in Lower Missourian stratum) include a new belinurid xiphosuran with fungal hyphae traces (?) on prosoma; a new Calvertiellid Paleodictyopteran; the co-occurrence of blattoid species Archimylacris n. sp., Opsiomylacris cf. thevenni, Phyloblatta cf. flabellata, Anthracoblattina cf. gigantea, Xenoblatta (Necymylacris) scudderi, Kinklidoblatta cf. lesquereuxii, Spiloblattina cf. allegheniensis, Spiloblattina cf. pygmaea, Sysciophlebia cf. balteata, and Poroblattina parvula requiring extensive revision of Carboniferous blattoid biostratigraphy; and a new Tcholmanvissidae orthopteran pre-dating the Oedischids of Commentry. The Cemetery Hill orthopteran is the second oldest known after the previously unreported Oedischids at Mazon Creek (Upper Desmoinesian) by Kukalova-Peck. The largest known fossil cockroach, from the ‘7-11 Mine’ at Cemetery Hill, is identified as Xenoblatta scudderi.