Trace fossils and tropical karst

Two crinoid pluricolumnals from Permian rocks of Timor show similar patterns of external pitting. Platycrinitid sp. preserves circular, parabolic pits that do not cross-cut between columnals, some have raised rims and at least one columnal shows a growth deformity. These pits are interpreted as the trace fossil Oichnus paraboloides Bromley. Crinoid sp. indet. has particularly dense pits cross-cutting columnals on one side of the pluricolumnal only and extending onto the contiguous limestone; it is a Holocene microkarstic solution feature. Care must be taken to separate true bioerosive trace fossils from modern microkarstic features in limestones in the tropics.