Methods for distinguishing carbonized specimens of the presumed cephalopod aptychusSidetes(Spathiocaris) from the plantProtosalvinia(Foerstia)

Abstract

The purpose of this note is to point out the similarities betweenProtosalvinia (Foerstia)andSidetes (Spathiocaris)and to discuss characters that can be used to distinguish the two taxa.ProtosalviniaClarke, 1885 (Figure 1.1-1.4), also commonly referred to by the junior subjective synonymFoerstia, is a plant fossil that is frequently noted as occurring in Upper Devonian black shale sequences of North America. This taxon has been of great interest to stratigraphers, paleoecologists, plant taxonomists, and plant morphologists over the years (see, for example, Winslow, 1962, p. 7, p. 22, fig. 3; Barron and Ettensohn, 1981, p. 30-31; Matthews, 1983; and Romankiw et al., 1988). Most workers in recent years have consideredProtosalviniato be a marine alga, but there is also evidence for a land plant affinity (Romankiw et al., 1988).