65-million-year-old giant fungus found in Chinese forests nicknamed D-rex

Deep in the tangled forests of southwest China, researchers have uncovered a fungal behemoth that upends expectations about how large ascomycete fungi can grow. The species, newly named Dianjunus rex — “King of Dian” — erupts from woody roots with towering, ivory-colored fruiting bodies that can reach roughly 20 inches in height and weigh as much as five pounds, making it one of the largest known members of its group.

An international team working across China, Thailand and Mexico has determined that this organism is not only a new species but represents an entirely new genus and family within the Ascomycota. Genome sequencing and morphological study suggest the lineage emerged about 65 million years ago, shortly after the mass extinction that ended the age of dinosaurs — a timing that raises intriguing questions about how forest ecosystems and wood-decomposing fungi rebounded after that global upheaval.

How scientists found Dianjunus rex in Yunnan’s mixed forests

Field teams from the Kunming Institute of Botany and partner institutions encountered the unusual fungi during surveys in Yunnan province, where temperate conifer stands blend into subtropical rainforest. The specimens appeared as conspicuous vertical stromata growing on the roots of Chinese cork oak, standing out in the leaf litter and understory debris.

The discovery involved:

• Targeted field searches across varied forest types in Yunnan.
• Collection of intact fruiting bodies for lab-based study.
• Isolation of spores and cultivation on nutrient media to observe growth and microscopic features.

Lab work revealed a stable, distinctive morphology that did not match known families in the order Xylariales, prompting genomic sequencing and broader taxonomic comparisons.

What makes Dianjunus rex physically remarkable

This fungus stands out for its sheer scale and structure. Unlike typical ascomycetes, which release spores from small sack-like asci embedded in their fruiting tissues, D. rex develops large, upright stromata — a growth form that allows it to tower above surrounding detritus.

Key physical traits:

• Fruiting bodies up to ~20 inches (about 50 cm) tall.
• Individual specimens weighing up to approximately 5 pounds.
• Whitish, robust stromata attached to woody roots, especially of Chinese cork oak.
• Spores and microscopic features consistent with placement in Ascomycota, but distinct enough to warrant a new family.

Such a large, energy-intensive fruiting structure is rare among ascomycetes; prior record-holders typically measured 20–30 centimeters tall, making D. rex roughly twice as tall as the largest previously known relatives.

Genetic evidence: a new family and an ancient origin

Genomic sequencing and phylogenetic analysis established that D. rex belongs to a previously undescribed lineage now named Dianjunaceae. Comparative DNA work placed this family within the Xylariales order, with Graphostroma platystoma appearing as its closest known relative.

Researchers applied molecular clock methods to estimate when Dianjunaceae separated from other xylariaceous fungi. By comparing sequences to hundreds of fungi with known divergence dates, they inferred an origin of roughly 65 million years ago — notably soon after the Cretaceous–Paleogene (K–Pg) extinction event.

Why the timing matters

The post-extinction interval saw dramatic changes in plant communities and the rapid accumulation of dead woody material as ecosystems reorganized. That surplus of substrate could have created new ecological opportunities for wood-decaying fungi, potentially favoring traits like large fruiting bodies that improve spore dispersal in dense, recovering forests.

As one of the study’s lead authors noted, the lineage provides “a rare window into the evolution of extreme fungal body forms,” highlighting how environmental upheaval may spur dramatic morphological innovation.

Ascomycota: the influential fungal phylum that includes D. rex

Ascomycota is the largest fungal phylum, with more than 64,000 described species. Members of this group don’t form classic gilled mushrooms; instead they bear spores in microscopic sacs (asci) within or on their fruiting tissues. Despite that technical difference, ascomycetes are central to human life and ecosystems.

Examples of Ascomycota’s roles:

• Food and fermentation: yeasts and molds used in bread, beer, wine, soy sauce and many cheeses.
• Medicine: production of antibiotics like penicillin and immunosuppressants such as ciclosporin.
• Culinary delicacies: prized fungi such as morels and truffles are ascomycetes.
• Pathogens and pests: species that cause Dutch elm disease, chestnut blight, powdery mildew and human infections.

Within this vast phylum, D. rex stands out not just for size but for its potential to reveal how extreme morphological strategies evolve in fungi.

Ecological implications: why grow so big?

Producing a large, upright fruiting body likely reflects a trade-off between reproductive payoff and metabolic cost. In dense forest understories, a tall stromata might reach air currents above the low vegetation, enhancing wind-borne spore dispersal. At the same time, constructing such a structure demands significant nutrient and energy investment — something only sustainable if the ecological benefits compensate.

Researchers propose several reasons D. rex might have evolved gigantism:

• Enhanced spore release and dispersal in cluttered forest environments.
• Adaptation to abundant woody substrates following large-scale vegetation turnover.
• Niche specialization on root-associated wood decomposition where larger stromata confer a competitive advantage.

What this discovery means for fungal biodiversity in East Asia

The find underscores that subtropical and temperate forests in southwest China remain hotbeds of undescribed fungal diversity. The region’s climate stability, habitat variety and complex ecological networks foster speciation, but field obstacles have historically limited surveys.

Challenges that have slowed fungal discovery here include:

1. Difficult terrain and seasonal accessibility of remote forest sites.
2. Short, unpredictable fruiting seasons that hide many species most of the year.
3. Past scientific focus on economically important fungi, leaving ecological specialists under-sampled.

The authors expect more unusual and taxonomically significant fungi to emerge from expanded fieldwork and genomic screening in the region, especially as molecular tools make it easier to place enigmatic specimens in an evolutionary context.

Next steps: research directions and conservation concerns

Moving forward, scientists plan to:

• Survey broader geographic ranges to determine the distribution of Dianjunaceae.
• Study the species’ life cycle, substrate preferences and ecological interactions in situ.
• Use population genomics to understand diversity within the new family and its evolutionary history.

Protecting the habitats where such fungi are found will be essential if researchers hope to document and preserve these unique lineages, since forest loss and climate change could erase species before they are described.

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Michael Thompson

Michael Thompson is an experienced journalist covering U.S. and global news. With ten years on the front lines, he breaks down political and economic stories that matter. His precise writing and keen attention to detail help you grasp the real‑world impact of every event.