Researchers Name China’s Largest Known Fungus

Researchers from the Kunming Institute of Botany identified Dianjunus rex in forest environments in Yunnan province, naming a fungus whose reproductive structure reaches about 50 centimetres and weighs up to 2.2 kilograms. Their work established not just a new species, but a new genus and family—Dianjunaceae—while the forest ecosystem where it grows remains under investigation.

The specimen’s scale sets it apart. It has the largest known fruiting body among fungi in the phylum Ascomycota, whose previously known fruiting bodies generally reached considerably smaller heights. The white structures, called stromata, grow from woody roots of Chinese cork oak trees.

A name, a genus, a family

Researchers first encountered the structures during surveys of forest environments in Yunnan. They initially suspected they had found an unfamiliar fungus. Laboratory work followed: the team examined physical characteristics, cultivated spores and analysed DNA before establishing Dianjunus rex as a new genus and the family Dianjunaceae.

That process places the discovery within formal scientific classification, with researchers using specimens and genetic analysis to determine where the fungus belongs. D-rex is part of the order Xylariales. Members of that order produce specialized compounds and enzymes that help break down complex plant material.

Researchers believe D-rex may obtain nutrients by decomposing dead wood, but its ecological role needs further study. The distinction matters: the fungus’s classification is established, while how it fits into the forest’s living systems is still being worked out. The available research describes a possibility, not a settled account of its role.

A lineage older than its discovery

Molecular-clock analysis compared D-rex’s genetic information with that of hundreds of other fungal species. The analysis suggests Dianjunaceae originated around 65 million years ago, approximately one million years after the Cretaceous-Paleogene mass extinction that wiped out non-avian dinosaurs.

That timeline has led researchers to consider whether environmental changes after the extinction created opportunities for wood-decomposing fungi to diversify. Changes in forest ecosystems and the availability of dead plant material may have helped ancestral fungi diversify. Researchers present this as a possible explanation, not a proven cause.

Scientists are also investigating why D-rex grows such large reproductive structures. One possibility is that height helps spores disperse by carrying them above forest-floor vegetation and debris, where they may catch air currents. The fungus’s size requires considerable energy; researchers say it may be advantageous under particular forest conditions rather than a strategy beneficial to every fungus.

What the forest still hides

The discovery adds to evidence of biodiversity in East Asian forests, where difficult terrain, seasonal growth and fungi’s often-hidden nature make species challenging to document. Researchers say further exploration may reveal other fungal forms and provide insight into evolution, forest ecosystems and undiscovered biodiversity.

For now, D-rex is both a remarkable specimen and an open question. Its height and weight can be measured, and its place in a newly established family has been described. Its ecological role, the reason for its size and what else may be growing beyond the reach of current surveys remain subjects for further study. Image credit: Kunming Institute of Botany / Chinese Academy of Sciences.