Deep in the forests of southwest China, scientists have discovered a massive new fungus named Dianjunus rex that towers up to 20 inches high and weighs up to 5 pounds. Researchers report that its unique evolutionary lineage arose approximately 65 million years ago, striking soon after the dinosaur-ending mass extinction.
Fieldwork conducted across Yunnan province uncovered large, whitish fruiting bodies growing directly from the rhizosphere on the woody roots of Chinese cork oak. Researchers identified the specimens during expeditions into temperate coniferous forests near Damaidi and Yipinglang, as well as tropical rainforest terrain near Nanbang. These structures, scientifically known as stromata, represent an entirely new genus and an entirely new family of fungi designated as Dianjunaceae.
Dianjunus Rex Claims Record Size Among Ascomycete Fungi
Producing vertical fruiting bodies measuring up to 50 centimeters tall and scaling weights up to 2.2 kilograms, the newly described organism is the largest known within the phylum Ascomycota. Ascomycetes constitute the largest group of fungi with more than 64,000 recognized species, encompassing familiar molds, yeasts, morels, and truffles. Prior to this find, record-holding fruiting bodies among ascomycetes maxed out between 20 and 30 centimeters in height, making the newly discovered giant roughly double the height of previous record holders.
Scientists from the Kunming Institute of Botany gathered the specimens and deposited voucher specimens into institutional collections. The team cultivated spores on nutrient media to analyze morphological traits and extracted genomic data, including protein-coding genes. Their combined genetic and morphological analysis confirmed that the fungus represents a new species, genus, and family placed within the order Xylariales.
Molecular Analysis Traces Evolutionary Origins to the Paleocene
Using molecular clock analysis on the organism’s DNA and comparing it against the genomes of hundreds of fungi with established evolutionary ages, researchers estimated that Dianjunaceae emerged around 65 million years ago. This timeline places the emergence of the family roughly one million years after the Cretaceous-Paleogene mass extinction event that wiped out the dinosaurs alongside countless plant and animal species.
The closest known living relative to the newly discovered giant is Graphostroma platystoma, a wood-decaying species that inhabits dead hardwood throughout the Northern Hemisphere and forms its own family, Graphostromataceae. Xylariales fungi are widely recognized for producing specialized enzymes and secondary compounds capable of breaking down complex plant molecules, an adaptive trait that likely aids the newly found organism in digesting tough wood.
Ecological Opportunities Following Ancient Mass Extinction
The close temporal alignment between the rise of the fungal lineage and the post-dino extinction period points toward specific ecological shifts in ancient forests. Massive ecosystem disruptions left vast reserves of dead plant material in their wake, potentially creating novel niches for wood-decomposing organisms.
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.
Dr. Indunil C. Senanayake, corresponding author of the study published in Frontiers in Fungal Biology
To explain why the organism maintains such massive proportions today, researchers suggest that structural height provides clear survival advantages in dense forest canopies. Elevating reproductive structures high above forest floor debris and surrounding vegetation allows better dispersal of spores by wind. However, building and maintaining such a towering fruiting body demands substantial energy investments, indicating that the strategy persists only where ecological advantages outweigh metabolic costs.
Subtropical Forests of Southwest China Hold Hidden Diversity
Researchers emphasize that subtropical ecosystems in China remain underexplored due to challenging field logistics, the seasonal and cryptic nature of fungal fruiting cycles, and a traditional scientific focus on economically valuable species. The region’s unique blend of habitat diversity, stable climates, and complex biological interactions creates an ideal crucible for fungal diversification.
Scientific teams anticipate uncovering further novel fungal taxa as fieldwork continues throughout subtropical and tropical regions of southwestern China. The formal description of the species and its associated lineage was published in Frontiers in Fungal Biology under the formal study title detailing the new Paleocene lineage.