New Giant Fungus ‘Dianjunus rex’ Discovered in China’s Yunnan Forests

Dianjunus Rex Emerges as a 2.2-Kilogram Fungal Giant in Yunnan Forests

Scientists have discovered a massive subterranean fungus in southwestern China weighing up to 2.2 kilograms and standing 50 centimeters tall, representing an entirely new family that researchers have named Dianjunus rex. The specimen shatters expectations for the order Xylariales by producing towering, fleshy reproductive structures known as stromata that emerge from the roots of dead trees in Yunnan Province.

Photo: Global Times

The soft yellow columns look quite different from related fungi, reaching about 8 inches (20 centimeters) to 50 centimeters in total height, including a buried stalk, with fertile parts measuring 10 to 20 centimeters high and 7 to 10 centimeters in diameter, sometimes reaching 15 centimeters. While typical individual stromata weigh between 250 and 600 grams, the largest bilobed specimen recovered during the field surveys tipped the scales at 2.2 kilograms, which researchers also reported as a maximum weight of about 4.9 pounds.

Genomic Profiling and Evolutionary Lineage Dating

To establish the identity of the organism, researchers combined physical examination with genetic sequencing and genome-scale analyses across four key genetic regions: ITS, LSU, RPB2, and TUB2. The resulting phylogenomic analyses consistently placed the species in a distinct evolutionary lineage related to Graphostromataceae, yet distinct enough to warrant a brand-new family, Dianjunaceae. Global Times noted that unlike familiar edible mushrooms belonging to Basidiomycota, Dianjunus rex belongs to Ascomycota. Researchers estimate that this lineage diverged around 65 million years ago, placing its origins directly in the early Paleocene following the Cretaceous–Paleogene extinction event.

Photo: Daily Kos

The study, published in Frontiers in Fungal Biology and titled Unearthing a fungal giant: Dianjunaceae fam. nov., a novel Paleocene lineage of Xylariales harboring Dianjunus rex gen. et sp. nov, establishes the newly established family with just one known member. The Cretaceous–Paleogene mass extinction occurred about 66 million years ago and wiped out an estimated 75% of plant and animal species, including non-avian dinosaurs such as Tyrannosaurus rex. Genes encoding pectin lyases were almost absent, with zero or one such gene compared with 7 to 19 in closely related Xylariales, while glycosyltransferases accounted for about 25.9% to 26.0% of its carbohydrate-active enzyme repertoire.

Field Collection and Subtropical Habitat Dynamics

Specimens of the giant fungus were gathered during biodiversity surveys conducted between August 2024 and July 2025 across subtropical and tropical forests in Yunnan Province. Earth.com detailed that the collections occurred in the tropical rainforests of Xishuangbanna Dai Autonomous Prefecture as well as temperate coniferous forests in Kunming and Lufeng. The upright, fleshy stromata vary in shape from cylindrical and spindle-shaped to palm-shaped. While typical individual stromata weigh between 250 and 600 grams, the largest bilobed specimen recovered during the field surveys tipped the scales at 2.2 kilograms.

Indunil Senanayake, an associate professor at the Germplasm Bank of Wild Species of the Kunming Institute of Botany, emphasized the implications of the find for regional biodiversity. The discovery illustrates how much fungus biodiversity remains to be discovered in East Asian forests, Senanayake stated, noting that Yunnan harbors over 6,000 documented fungal species while estimated totals exceed 100,000. Researchers have also hypothesized that the fungus might initially live harmlessly inside living trees before feeding on their remains after death, though this life cycle remains unconfirmed.

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