A pale-yellow fungus up to 50 cm (20 inches) tall, growing from the roots of dying trees in China’s Yunnan province, belongs to a lineage that may have originated in the aftermath of the dinosaur extinction.
Stromata of Dianjunus rex in the field. Image credit: Song et al., doi: 10.3389/ffunb.2026.1940464.
“This remarkable species represents a new fungal family and provides a rare window into the evolution of extreme fungal body forms,” said Dr. Indunil Senanayake, a researcher at the Kunming Institute of Botany.
“The discovery illustrates how much fungus biodiversity remains to be discovered in East Asian forests.”
Named Dianjunus rex, the species produces fleshy, finger-like or palm-shaped fruiting structures, called stromata, up to 50 cm tall. The largest specimen weighed 2.2 kg (nearly 5 pounds).
Its fresh fruiting bodies are soft and dry out quickly once picked.
“A fruiting body which towers above surrounding vegetation and debris could have better dispersal of spores by wind in dense forests,” Dr. Senanayake said.
“However, such a large structure requires substantial energy investment, suggesting that this strategy likely evolved only where the ecological benefits outweighed the costs.”
The specimens of Dianjunus rex were collected in 2024 and 2025 at three sites: a tropical rainforest in Xishuangbanna and temperate forests near Kunming and Lufeng. Most of them were found attached to the roots of oak trees.
“They grew on woody roots of Chinese cork oak, emerging from the rhizosphere,” Dr. Senanayake said.
“Ascomycetes, with more than 64,000 species the largest group of fungi, don’t grow true mushrooms but instead release spores from tiny, sac-like structures inside or on the surface of such fruiting bodies.”
Dianjunus rex belongs to the Xylariales, a large order of fungi that mostly decompose wood and typically form small, dark, crusty growths.
Genetic analyses of four gene regions, plus whole-genome sequencing of three specimens, placed the species on its own branch, a sister to a family called Graphostromataceae.
Its pale, powdery surface, distinctive spore features and microscopic asexual stage set it apart, justifying a new family, Dianjunaceae.
By comparing genomes with those of calibrated fungal lineages, the researchers estimated that the family split off about 65 million years ago.
This would put its origin around the end-Cretaceous mass extinction that wiped out the non-avian dinosaurs.
“This timing raises an intriguing possibility,” Dr. Senanayake said.
“After the mass extinction, forests experienced dramatic changes, including the sudden availability of large amounts of dead plant material.”
“For wood-associated decomposing fungi, such environmental disruption may have created new ecological opportunities.”
The discovery is reported in a paper in the journal Frontiers in Fungal Biology.
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Jing Song et al. 2026. Unearthing a fungal giant: Dianjunaceae fam. nov., a novel Paleocene lineage of Xylariales harboring Dianjunus rex gen. et sp. nov. Front. Fungal Biol 7; doi: 10.3389/ffunb.2026.1940464
