The trace Rhopalia clavigera isp. n. reflects the development of its maker Eugomontia sacculata Kornmann, 1960

Complex boring patterns often reflect the complexity of life cycle of the euendoliths that produce them. They are illustrated here by different stages in the development of the euendolithic ulotrichacean chlorophyte Eugomontia sacculata reconstructed on the basis of its complex trace in the shells of Mya arenaria in brackish waters of the Baltic Sea at Gdansk, Poland. The trace consists of different types of boring morphologies as distinctive from one another as many traces specific to separate organisms. Because they occur associated, they may be misinterpreted as separate members of an ichnocoenosis. We propose to describe them as parts of a complex trace instead, because they are based on the genetic program of a single organism, but expressed in different proportions at different stages of its development. A new ichnospecies, Rhopalia clavigeraisp. n., is described to characterize these traces.