Myxogastria - Fossil Records

Fossil Records

Fossil records of Myxogastria are extremely rare. Due to their short lifespan and the fragile structures of the plasmodia and the fruit body, fossilisation and similar processes are not possible. Only their spores can be mineralised. The few known examples of fossilised living states are preserved in amber. Up to 2010, three fruit bodies, two spores and one plasmodium have been described. Two older taxa – Charles Eugène Bertrand's Myxomycetes mangini and Bretonia hardingheni from 1892 – are now considered dubious and are today often disregarded. Friedrich Walter Domke described in 1952 a 35 to 40 million year old find in Baltic amber of Stemonitis splendens, an extant species. The state and completeness of the fruit bodies are remarkable, enabling accurate determination. From the same period, location and material is an Arcyria sulcata, first described in 2003 by Heinrich Dörfelt and Alexander Schmidt, a species very similar to today's Arcyria denudata. Both discoveries imply that the fruit bodies of the Myxogastria have changed only slightly in the last 35 to 40 million years.

However, the Protophysarum balticum from Baltic amber, first described by Dörfelt and Schmidt in 2006, is considered questionable. The fossil was inconsistent with the typical characteristics of the genus and it was not a valid publication because no Latin name was identified with it. Also, important details of its fruit bodies were not visible or contradicted the identification. Today it is assumed that the fossil belongs to a lichen similar to the genus Chaenotheca. The only known discovery of a preserved plasmodium was found in amber in the Dominican Republic, and was then grouped into the Physarida. However, this claim is also considered doubtful as the publication was later classified as insufficient due to lack of evidence. The only known mineralised fossils are the two spore findings from 1971, one of which, Trichia favoginea, is assumed to be from the postglacial period. In palynologian researches, by absorbing Myxogastria spores, the fossil was not recognised.