Ichnofossil--Shanwangichnus diatomus ichnogen. et ichnosp. nov. Yang described here isthe first contribution from the ichnological materials, which have been recovered from Miocene diatomaceous shale of the Shanwang basin.Ichnofossil--Shamuangichnus diatomus is a fodinichnia, full relief preservation. It is astraght to sub-sinuous tubular burrow, which is parallel or subparallel to the bedding planes. The tubes may be unbranched or occasionally branched. The two limbs of the burrow may be subpar-allel to each other, and may be closed at one side and open at the other. The diameters of the burrows range from 2 to 2. 5 mm, and exhibit only minor change in dimension along their length. An attempt has been made to speculate the organism that is presumably responsible for Shamuangichnus diatomus, which may probably be the representative of Oligocheata worms.