Fish Swimming Traces from the Upper Devonian of Wuhan, South China

Marine vertebrate trace fossils are relatively scarce in the geological record. Here we report on fish swimming traces from the marginal-marine deposits of the Upper Devonian Wutong Formation in Wuhan, South China, which provide information about the composition and ethology of the benthic vertebrate ichnofauna. The fish trails are mainly preserved as irregular or regular, single, paired, or intertwined sinusoidal waves on the upper bedding plane of a quartz sandstone bed. They are ascribed to Undichna unisulca, U. bina, U. cf. britannica, U. cf. trisulcata, U. cf. quina, and U. isp. On the basis of detailed morphological analysis and background data on the Devonian fish fauna, antiarch placoderms and other types of gnathostomes are proposed as possible makers of the trails. Antiarchs are equipped with the typical bony pectoral fins and are probably responsible for U. cf. trisulcata associated with straight marks, as well as for the gradational U. cf. britannica. Jawed fishes with generally high swimming skills and multiple paired fins may have produced the more regular and complex patterns like U. bina and U. cf. quina. The densely distributed, irregular undulatory U. isp. showing frequent cross-cutting relationships likely resulted from a school of small-sized gnathostome fishes.