Deep-sea ecosystem revealed by teleost fish coprolites from the Oligocene of Poland

Non-spiral coprolites likely produced by teleost fish were studied from deep-sea sediments of the Oligocene (Rupelian) of Poland. The materials were collected at the Futoma and Wola Czudecka localities of the Dynów Marl Member of the Menilite Formation, Western Carpathian Mountains. The coprolites are elongate, linear, slightly to strongly sinuous and vary in size (maximal diameter from 1.25 to 10 mm) but appear to show a morphologic continuum rather than represent several morphotypes. Phosphatic matrix is preserved in 81% (13/16) of the specimens and is composed primarily of putative fossilized bacteria. The matrix contains numerous cavities possibly formed by gas bubbles or decomposition of organic matter, and also an oval object resembling invertebrate eggs or another organic object. At least 81% (13/16) of the coprolite specimens contain fish remains (bones, scales, a tooth), which in some specimens include elements attributable to the predatory fishes Palimphyes, Oligophus and an indeterminate gadiform. This is indicative of fish predation upon other predatory fishes in this marine environment, which probably exceeded 500 m of depth. The coprolites are interpreted as produced by pelagic fish that lived in the oxygenated higher parts of the water column, while the fecal matter sank and was deposited in anoxic conditions on the sea bottom. Identification of non-spiral coprolites of fish and the fossil record of teleost coprolites are discussed.