Dianjunus Rex, a Giant Fungus From Yunnan, Gets a Brand-New Family

In the forests of Yunnan, China, a fungus sends up stalks as tall as 50 centimeters (about 20 inches) and as heavy as 2.2 kilograms (close to a 5-pound bag of sugar, which is a lot of sugar for something with no arms). Scientists named it Dianjunus rex. Most royal titles are a stretch. This one checks out.²

An international team from China, Thailand and Mexico described the species in a new study in Frontiers in Fungal Biology.⁴ The authors say its fruiting bodies are the largest ever documented in the phylum Ascomycota, one of the biggest branches of the fungus family tree.² That record claim comes from the researchers themselves. No outside group has confirmed it yet, so for now the crown is self-reported.

Royalty, party of one: why it needed a new family

A fruiting body is the part of a fungus that rises up to release spores. In this species, scientists call those upright structures stromata. The name rex is Latin for king, a nod to their large size and majestic look.⁴ (Fungi are rarely called majestic. Usually they get called something in the yard.)

The bigger surprise is where it fits. Scientists sort living things into nested groups: species, then genus, then family, then order. Dianjunus rex was different enough to need a brand-new genus and a brand-new family, called Dianjunaceae, and it is the only known member of both.²³ That makes it the president, the treasurer and the entire potluck. The family sits within an order of fungi called Xylariales, as a distinct sister branch to a family called Graphostromataceae.³ So it does have a sibling. It just prefers its own house.

“This remarkable species represents a new fungal family, Dianjunaceae, and provides a rare window into the evolution of extreme fungal body forms,” said corresponding author Dr. Indunil C. Senanayake, an associate professor at the Germplasm Bank of Wild Species at the Kunming Institute of Botany, in the Frontiers press release.²

Family roots reaching back 65 million years

The team sequenced the fungus’s genome and ran a molecular-clock analysis. That method uses the pace of genetic change to estimate when groups of living things split apart, a bit like dating an old family photo by the haircuts.¹³

The result: the family likely arose about 65 million years ago, in the early Paleocene. That was soon after the K-Pg mass extinction, the dinosaur-era disaster that wiped out an estimated 75% of species.³ The researchers suggest the upheaval may have opened new niches for fungi that break down wood.² In other words, the worst day in dinosaur history may have been a decent career opportunity for wood rot.

To be clear, that is an estimate for the age of the family line, not any single fungus. Nobody is claiming a 65-million-year-old fungus is sitting under an oak in Yunnan, waiting for someone to ask about the old days.

Where the king holds court (mostly on oak roots)

Scientists from the Kunming Institute of Botany found the fruiting bodies during fieldwork in temperate coniferous forests near Damaidi and Yipinglang, and in tropical rainforest near Nanbang.² The fungus grows on the woody roots of Chinese cork oak, Quercus variabilis.¹ The study notes that stromata from tropical collections are larger than those from subtropical ones.⁴ Some of us also do better somewhere warm.

The holotype, the official reference specimen that defines the species (think of it as the photo on the species’ ID card), was collected at Damaidi in Luquan County, Kunming, on Aug. 5, 2024.⁴ The team stored voucher specimens at the Kunming Institute of Botany and grew spores in the lab to study the fungus’s structure.¹ The new names were registered in MycoBank, a database of fungus names, on Oct. 2, 2026.⁵ Paperwork: the one thing even a king can’t skip.

Why grow so big? The authors speculate that tall fruiting bodies may help spores spread through dense forests.² Same logic as standing on a chair at a crowded concert.

The researchers say the find highlights how much fungal diversity in East Asian forests is still unexplored.³ If something as heavy as a bag of sugar could go unnamed until now, the sugar-packet-sized stuff has plenty of places to hide, and is presumably counting on it.