Meet D-Rex, a Newly Discovered 5-Pound Fungus With a 65-Million-Year-Old Lineage
Learn why researchers suspect this fungus lives quietly inside healthy trees before feeding on their remains after they die.
In August 2024, researchers Jing Song and Indunil Senanayake discovered distinct specimens of an unusual fungus in Yunnan Province, China. These specimens, collected from oak root areas, marked the beginning of a series of collections aimed at identifying a new species. The study in Frontiers in Fungal Biology presents Dianjunus rex, a 5-pound fungus belonging to a newly identified family, Dianjunaceae, with an evolutionary lineage dating back 65 million years.
Genome analysis reveals that Dianjunus rex has fewer carbohydrate-digesting enzymes compared to its wood-rotting relatives, suggesting it may live quietly within healthy trees until they begin to die. The fruiting bodies of this fungus, which are powdery and whitish to yellow outside and spongy inside, were larger than the others, with the heaviest specimen weighing about 5 pounds.
The researchers collected five specimens in total during 2024 and 2025 in various forests, including coniferous forests near Kunming and Lufeng, and a tropical rainforest in Xishuangbanna. By comparing the DNA of the Dianjunus rex with that of other fungi, they placed it within the Xylariales group, its closest relative being Graphostromataceae. However, the fungus displayed enough differences in shape, spores, and genes to warrant a new genus and family.
The researchers used a molecular clock analysis to estimate the time of the fungus's divergence from a common ancestor, with results ranging from 50 to 80 million years ago. This timeframe corresponds with the mass extinction event that ended the dinosaurs, suggesting that the fungus's ancestors might have adapted to new ways of living as forests recovered.
The genus name, Dianjunus, pays homage to the Dian Kingdom, a past society in Yunnan, while the species name, rex, is Latin for king, referencing the fungus' size and imposing appearance. The team anticipates that more undiscovered fungi may exist in subtropical forests across China, highlighting the vast potential for fungal biodiversity in the region.
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