Paleolimulus, an early limuline (Xiphosurida), from Pennsylvanian±Permian LagerstaÈtten of Kansas and taphonomic comparison with modern Limulus LOREN E. BABCOCK, DANIEL F. MERRIAM AND RONALD R. WEST Babcock, L.E., Merriam, D.F. & West, R.R. 2000 09 15: Paleolimulus, an early limuline (Xiphosurida), from Pennsylvanian±Permian LagerstaÈtten of Kansas and taphonomic comparison with modern Limulus. Lethaia, Vol. 33, pp. 129±141. Oslo. ISSN 0024- 1164. The Pennsylvanian±Permian horseshoe crab Paleolimulus signatus (Beecher), incorpor- ating as a junior synonym P. avitus Dunbar, is one of the earliest species of the Limuli- na (Xiphosurida). Some specimens from Kansas, USA, are exceptionally well preserved, retaining intact book gills and appendages. Indistinct, bilobed burrowing traces of vari- able width occur in association with some examples of P. signatus and may have been produced by that animal. Based on actualistic taphonomic experiments on Limulus polyphemus, ancient horseshoe crabs and other arthropods having non-mineralized exoskeletons are inferred to have become pliable soon after death or moulting, and to have disarticulated slowly prior to burial. Extreme compression, wrinkling, and loose folding of sclerites are attributed to burial of a pliable exoskeleton. Slow preburial dis- articulation partly accounts for the exceptional preservation of Paleolimulus remains. Also relevant for the exceptional preservation of these arthropods was burial in estuar- ine, tidal ¯at, or lacustrine environments. Because of ¯uctuating salinity and possibly dessicating conditions, these settings were limiting to scavengers, burrowers, and some microbes that could potentially disarticulate or decompose xiphosurid remains. & Arthropod, horseshoe crab, Kansas, Pennsylvanian, Permian, taphonomy, Xiphosurid. Loren E. Babcock, Department of Geological Sciences, The Ohio State University, Colum- bus, Ohio 43210, USA [
[email protected]]; Daniel F.