 A fungal mycelium containing abundant clamp connections was found that dated to the Pennsylvanian era (298.9–323.2 Mya).This fossil, classified in the form genus "Palaeancistrus", has hyphae that compare with extant saprophytic basidiomycetes.The oldest known clamp connections exist in hyphae present in the fossil fern "Botryopteris antiqua", which predate "Palaeancistrus" by about 25 Ma.