A fresh look at sideritic "coprolites"

Sideritic "coprolites" from the late Miocene of southwest Washington, the U pper Cretaceous of Saskatchewan and Madagascar, and the Permian of China ha ve often been claimed to be pseudofossils. They are here interpreted as int estinal casts (cololites) prefossilized by bacterial activity and later tra nsformed into siderite with no traces of original food particles left. All occurrences are found within fluvial overbank deposits that carry no other vertebrate remains. Their absence could be due to aquifer roll-fronts that destroyed phosphatic bones and teeth but favored siderite precipitation.