Zwergimyces vestitus (Kidston et W.H. Lang) nov. comb., a fungal reproductive unit enveloped in a hyphal mantle from the Lower Devonian Rhynie chert

An interesting fungal reproductive unit, Zwergimyces vestitus (Kidston et W.H. Lang) nov. comb., occurs in degraded plant axes from the Lower Devonian Rhynie chert. Specimens are (sub-)globose, 40(–50) μm in diameter, and characterized by an outer hyphal and inner non-hyphal investment. The inner investment appears to increase in thickness as the reproductive unit matures. The fossil was initially described as Palaeomyces vestitus; however, based on the distinctive morphology we transfer this form to a new genus, for which the name Zwergimyces nov. gen. is proposed. Zwergimyces vestitus resembles not only the mantled zygosporangia of certain extant zygomycetous fungi, but also the spores of some Glomeromycota. Evidence of gametangial fusion, which could be used to positively identify a zygomycetous fungus, is lacking. The fossils are nonetheless noteworthy because they represent the oldest evidence of mantled fungal reproductive units.

► A mantled fungal reproductive unit from the Rhynie chert is reconsidered.
► The new combination Zwergimyces vestitus is introduced.
► Affinities of the fossil lie with the zygomycetous fungi or Glomeromycota.
► Oldest fossil evidence of hyphal mantles in fungal reproductive units