Girvanella‐like structures formed by Plectonema gloeophilum (Cyanophyta) from the Borrego Desert in Southern California

Abstract

An example of a recent tubiform fossil Girvanella is reported from a transitory, freshwater flash‐spring, in an area of the Borrego Desert, near San Diego, California. It occurs as the preserved, calcite‐impregnated sheath of the blue‐green alga Plectonema gloeophilum Borzi. In size and form, the fossil is identical to the first specific description of a recent Girvanella. The data presented give strong support to the idea of specificity for calcification in some blue‐green algae.