Pellicle ultrastructure demonstrates that Moyeria is a fossil euglenid

Abstract

An earlier proposal of euglenid affinity for the acritarch Moyeria was based primarily on the pattern of bi-helical striate ornamentation as seen in scanning electron microscopy and light microscopy. Examination of specimens using transmission electron microscopy reveals that the ‘striae’ are actually integral components of the microfossil wall itself, corresponding to the pellicle strips of some euglenid species today. A Silurian specimen from Scotland preserves an articulated wall composed of thickened arches and thinner U-shaped interconnecting segments paralleling that seen in some modern photosynthetic euglenids. A second specimen from the Moyeria holotype section (Silurian of New York State) shows fused articulation, again compatible with some extant euglenids. This evidence is sufficient to transfer Moyeria out of the Incertae sedis group, Acritarcha, and into the Euglenida. This proposal helps establish the morphological basis for the recognition of euglenid microfossils and ultimately provides evidence of a lengthy fossil record of the eukaryotic supergroup Excavata.