MILLIPEDS (DIPLOPODA) FROM THE FORT SILL FISSURES (LOWER PERMIAN) OF SOUTHWESTERN OKLAHOMA: RARE EXAMPLES OF PERMIAN MILLIPEDS AND OF FOSSIL MILLIPEDS FROM A PALEOZOIC FISSURE FILL

Several taxa of rare Permian millipeds have been found in a new fossil-producing pocket of the Fort Sill fissures exposed in the Dolese Quarry in southwestern Oklahoma. Permian millipeds are very rare, especially so considering their relative abundance during the preceding Carboniferous. The forms found here are elongate (helminthomorph) millipeds, with up to about twenty midbody segments preserved. Pleurotergal ornamentation varies from simple ridges and striae to exquisitely preserved, reticulate microsculpture. Probable ozopores and coxal segments are preserved on some material. The fossils were found in greenish clay cave-fill and calcite-cemented rock, and calcite crystals adhere (or did adhere before preparation) to some of the millipede material. The fissure fill with the millipedes also contained several taxa of amphibians and reptiles not previously known from this site. Interestingly, the main animal found at the site, Captorhinus aguti, is a possible predator of arthropods.

Fossil myriapods (millipeds and centipeds) have been previously described from karst deposits (caves and fissure fills) in a number of localities including Europe (Greece, Austria, Hungary, Romania), South Africa, and the Caribbean (Jamaica). These karst deposits were formed in a variety of climatic regimes ranging from the tropics (e.g., Jamaica) to cooler mountainous (e.g., Transylvania and South Africa) climes. Carbonate mineralization of and around myriapods (especially millipeds with their already carbonate-rich cuticles) is common in both lowland and highland, and tropical to cooler, environments, as is three-dimensional preservation. Most previous accounts of cave and fissure-fill myriapods (almost all millipeds) are of Pleistocene (or at least Cenozoic) occurrences of forms that are closely allied to modern taxa.