ISOTELUS (TRILOBITA) HUNTING BURROW FROM UPPER ORDOVICIAN STRATA, OHIO

Recurring associations of the trilobite ichnogenus Rusophycus with var ious ''worm'' burrows suggest an interaction between the two tracemake rs, specifically, capture of the worm by the trilobite. An exceptional ichnofossil from the Upper Ordovician of southwestern Ohio shows char acters consistent with previously described ''trilobite hunting burrow s'' from Cambrian and Silurian strata. Preserved in convex hyporelief is R. carleyi, attributable to the trilobite Isotelus, on which is sup erimposed the case of a worm burrow of the ichnogenus Palaeophycus. Th e cast of the worm burrow appears to have been truncated by the diggin g activities of the trilobite, suggesting its predation of the worm. T he exquisite preservation of ventral axial morphology of the trilobite distinguishes this Rusophycus from simpler bilobate forms attributabl e to filter-feeding behavior. Congruency in the preservation of worm a nd trilobite trace supports the conclusion that both were created at t he same time, as the trilobite exited the intrastratal burrow. This is the first report of a trilobite hunting burrow from the Ordovician, a nd the first evidence for predatory behavior for the trilobite genus I sotelus.