Giant Fungus Dianjunus Rex Discovered in Yunnan
Scientists have identified Dianjunus rex, a fungus growing up to 20 inches tall and weighing nearly five pounds, as the largest known in its phylum.
Scientists have identified a giant fungus named Dianjunus rex in Yunnan, China. This fungus is the largest known in the Ascomycota phylum, with its fleshy, finger-like fruiting bodies reaching 50 centimeters tall and weighing up to 2.2 kilograms. It surpasses previous record-holders, which typically grew only 20 to 30 centimeters tall.
Most specimens were found attached to the roots of Chinese cork oak trees in temperate coniferous and tropical rainforest environments. The species was discovered at three sites in Yunnan province: a tropical rainforest in Xishuangbanna and temperate forests near Kunming and Lufeng. Its fresh fruiting bodies are soft and dry out quickly once picked.
Evolutionary breakthrough after mass extinction
The fungal family Dianjunaceae originated about 65 million years ago. This is roughly one million years after the Cretaceous-Paleogene mass extinction that wiped out the dinosaurs. Researchers used molecular clock analysis to estimate this evolutionary split.
The discovery suggests the post-extinction ecological upheaval created niches for wood-decomposing fungi like D-rex. Dr Indunil C Senanayake said: "This timing raises an intriguing possibility. After the mass extinction, forests experienced dramatic changes, including the sudden availability of large amounts of dead plant material." The study proposes that these environmental changes created favorable conditions for extreme fungal body forms to evolve.
Field discovery and scientific validation
Researcher Jing Song collected the first fungus sample on oak tree roots in Yunnan in August 2024. A month later, researcher Indunil Senanayake found a second sample in the same village. Further specimens were collected in 2025.
Scientists from China, Thailand, and Mexico confirmed it as a new species. Genetic analyses placed Dianjunus rex on its own branch, as a sister to the family Graphostromataceae. Its closest known relative is Graphostroma platystoma, which grows on dead hardwood in the Northern Hemisphere. The species was classified into the new family Dianjunaceae based on its pale powdery surface, distinctive spore features, and microscopic asexual stage. The name Dianjunus references the ancient Dian Kingdom of Yunnan and the Chinese word for fungus, while 'rex' means 'king' in Latin.
Ecological significance and future research
Dianjunus rex belongs to the Xylariales order, which mostly decomposes wood and typically forms small, dark, crusty growths. This giant fungus grows inside healthy trees and later shifts to feeding on dead wood. It uses that energy to build its large reproductive structures. Growing such a large body requires substantial energy, suggesting the strategy evolved where the benefits outweighed the costs. The tall structures may improve spore dispersal in dense forests.
Researchers expect many more undiscovered fungal species to be found in China's subtropical forests. This is due to the region's immense habitat diversity and historical under-sampling. Over 6,000 fungal species have already been recorded in the area, with experts estimating more than 100,000 species may still exist there. Dr Indunil C Senanayake stated that the discovery provides a rare window into fungal evolution and shows much fungal biodiversity remains undiscovered in East Asian forests.
Continued field surveys in these forests aim to document additional undiscovered species.
