Meet D. rex: Newly Identified Giant Fungus From China Claims the 'King' Title After the Dinosaurs

In the forests of Yunnan province in southwestern China, farmers had long seen a strange sight: pale yellowish, fleshy, fingerlike growths clustered around a dead tree. Some had even tasted them and reported no ill effects, according to study coauthor Indunil Senanayake of the Kunming Institute of Botany, though the fungus has not been tested for toxins. Nobody, she told CNN by email, treated it as important.

That changed when a curious local sent photos to scientists, who quickly saw they were looking at something unusual. The species is now named Dianjunus rex, and it was recorded during fungal diversity surveys in 2024 and 2025. The findings were published September 28 in the journal Frontiers in Fungal Biology.

The name nods to Tyrannosaurus rex, and the fungus earns the comparison on its own scale. Its upright reproductive structures, called stromata, can reach 20 inches (50 centimeters) tall, roughly the height of a carry-on suitcase, and weigh nearly 5 pounds (2.2 kilograms). It is the largest known member of the phylum Ascomycota, the most diverse fungal group, with about 65,000 species including morels, truffles and yeasts.

The previous record holder was a bulbous brown fungus from Kenya, Engleromyces goetzei, with a diameter of nearly 12 inches (30 centimeters) and a weight of around 7 pounds (3.2 kilograms), Senanayake said. The close relatives of D. rex among the ascomycetes, also called sac fungi, range from microscopic to a few inches tall.

D. rex is more than a new species. Genetic analysis and comparisons with other fungi showed it belongs to a new family, Dianjunaceae, which likely emerged about 1 million years after the asteroid impact that ended the Cretaceous Period. That extinction event killed all non-avian dinosaurs and roughly 75% of plant and animal life. Senanayake explained that photosynthesis was suppressed and huge quantities of dead leaves, wood, roots and carcasses accumulated. Decomposers like fungi could feed on that bounty while other life struggled.

Why this one grew so large is the next question. Senanayake noted that ascomycetes generally do not produce large stromata, since doing so wastes energy. Sac fungi expel their spores actively, and in D. rex the upper part of the fruiting body carries thousands of tiny spore-releasing pores. The forest floor in its habitat is densely covered with fibrous plant material that may trap spores. She suggested that rising high above the ground may help spores disperse more widely and improve reproductive success.

Kabir Peay, a professor of biology and Earth system science at Stanford who was not involved in the research, said finds like this point to the many exotic fungal forms not yet described. Fungi contribute to Earth's carbon cycle and support the health and nutrition of many plants, he noted, and understanding what they do begins with describing them.

That work is far from finished. Scientists have described around 150,000 fungal species, but estimates of the true number run from 2 million to 13 million. Peay called fungi vastly underappreciated and underdescribed. Much of a fungus is hidden as threadlike hyphae, collectively a mycelium, buried in soil, wood or vegetation, and the stromata appear only when conditions are right or the fungus nears the end of its life cycle. Finding one is often a matter of being in the right place at the right time, he said; otherwise even impressive mushrooms go unnoticed. Researchers now want to explain D. rex's size, and the survey work that found it continues.