Researchers from China, Thailand, and Mexico have identified an exceptionally large wood-decomposing fungus in Yunnan, southwest China. Named Dianjunus rex, or D-rex, the species produces upright fruiting bodies reaching 20 inches in height and weighing up to 5 pounds. Found on the woody roots of Chinese cork oak during fieldwork in temperate coniferous forests and tropical rainforest, it represents both a new genus and a new family, Dianjunaceae.
After collecting specimens, researchers cultivated spores, examined the fungus's morphology, and sequenced its genome. Their analysis placed the new family within the order Xylariales, part of Ascomycota, the largest fungal group, with more than 64,000 species. Unlike true mushrooms, these fungi release spores from tiny sac-like structures. A molecular-clock analysis, comparing genetic information with hundreds of fungi of known evolutionary age, dated the family's emergence to approximately 65 million years ago—about one million years after the mass extinction that eliminated the dinosaurs. Researchers suggest that the resulting abundance of dead plant material may have opened ecological opportunities for wood-decomposing fungi.
D-rex's dimensions substantially exceed those of previous ascomycete fruiting-body record holders, which measured about 20 to 30 centimeters tall. Its height could improve wind-driven spore dispersal by lifting reproductive structures above surrounding vegetation and debris, although the considerable energy required implies a trade-off between costs and benefits. Researchers also anticipate further fungal discoveries in subtropical China, where varied habitats, climatic stability, and complex biological interactions promote diversification.
