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As the dinosaurs disappeared around 66 million years ago, other forms of life adapted to a changing planet. A giant fungus recently identified in China is offering scientists new insights into fungal evolution and the remarkable biodiversity that remains undiscovered.
A newly identified fungus discovered in the forests of Yunnan province in southwestern China is drawing scientific interest due to its remarkable size and evolutionary background. Designated as Dianjunus rex, this species generates vertical reproductive organs capable of growing up to roughly 20 inches (50 centimeters) tall while tipping the scales at close to 5 pounds (2.2 kilograms).
Its name draws a comparison with Tyrannosaurus rex, the famous dinosaur often described as the king of prehistoric predators. Although the two organisms are vastly different, the name reflects the fungus’s remarkable stature among its relatives. Rather than ruling ancient ecosystems through predation, D. rex represents an unusual branch of fungal diversity whose evolutionary history may be connected to the environmental changes that followed one of Earth’s largest mass extinction events.
The findings were published on September 28 in the scientific journal Frontiers in Fungal Biology. Beyond introducing a previously unknown species, the research identifies an entirely new family of fungi and offers clues about how these organisms evolved and adapted to their environments.
A fungus that stands out for its size
One of the most distinctive features of Dianjunus rex is the size of its fruiting bodies, known as stromata. These reproductive structures grow upright and have a fleshy appearance, with elongated projections resembling clustered fingers.
When they first emerge, the stromata are pale yellow. Their color gradually darkens as the fungus matures. At their largest, these structures can reach approximately 20 inches in height, making them unusually large for members of their taxonomic group.
The finding holds special importance as D. rex falls under the phylum Ascomycota, representing one of the fungal kingdom’s most expansive lineages. This particular grouping encompasses entities as diverse as truffles, morels, and yeasts, besides countless microscopic or infrequently spotted wild species.
Before the discovery of D. rex, one of the largest known members of this group was Engleromyces goetzei, a bulky brown fungus found in Kenya. Its fruiting body can reach nearly 12 inches (30 centimeters) in diameter and weigh approximately 7 pounds (3.2 kilograms).
However, D. rex is distinguished by the impressive height of its reproductive structures alongside their unique growth patterns. Numerous closely related fungi barely reach a height of a few inches, whereas others are so diminutive that proper examination demands specialized laboratory instruments.
Stanford University biology and Earth system science professor Kabir Peay underscored the significance of identifying fungi possessing such atypical traits. He pointed out that remarkable specimens enable researchers to grasp the vast diversity of fungal morphologies that remain unrecorded by science.
How the extinction of the dinosaurs may have influenced fungal evolution
The evolutionary origins of Dianjunaceae, the newly identified family that includes Dianjunus rex, are another important aspect of the research. By analyzing genetic material and comparing the fungus with related organisms, scientists estimated that the family emerged approximately one million years after the asteroid impact that brought the Cretaceous Period to an end.
Approximately 66 million years ago, that cataclysmic event sparked a mass extinction capable of wiping out all non-avian dinosaurs alongside roughly 75% of the planet’s flora and fauna.
The environmental consequences were profound. Reduced sunlight disrupted photosynthesis, while large quantities of dead leaves, wood, roots and animal remains accumulated across affected ecosystems. These changes disrupted food webs and made survival difficult for many organisms.
Yet the abundance of dead organic material may also have created opportunities for decomposers. Fungi play a central role in breaking down dead plants and animals, returning nutrients to the environment and supporting the continued functioning of ecosystems.
Indunil Senanayake, a coauthor of the study and associate professor at the Kunming Institute of Botany in China, explained that these conditions may have benefited certain groups of fungi. Although the precise relationship between the mass extinction and the emergence of Dianjunaceae remains a subject for further investigation, the findings illustrate how major environmental disruptions can influence the evolution and diversification of life.
A local observation led to a scientific discovery
Researchers identified Dianjunus rex during fungal diversity surveys conducted in the forests of Yunnan province in 2024 and 2025. However, local residents had noticed the unusual organism before scientists began investigating it.
Farmers in the area had encountered clusters of fleshy, fingerlike structures growing around a dead tree. Despite its unusual appearance, the fungus had not previously attracted significant scientific attention.
That changed when a local resident shared photographs of the organism with researchers. The images prompted the team to investigate further, examine specimens and conduct genetic analyses to establish the fungus’s identity and evolutionary relationships.
Senanayake noted that a few residents had actually consumed the mushroom without suffering any apparent ill effects. Still, the investigators have failed to perform adequate toxicity assessments to determine its safety for consumption. Consequently, the lack of documented symptoms ought not to be viewed as proof that the organism is fit to eat.
The discovery has also raised questions about why D. rex develops such large reproductive structures. Ascomycetes generally do not produce enormous stromata, possibly because building and maintaining them requires considerable energy.
One possibility is that the fungus’s height offers a reproductive advantage. Its upper structures contain thousands of tiny pores through which spores are released. In the forest environments where the species grows, the ground is often covered with fibrous plant material that could interfere with the movement of spores.
By raising its reproductive structures above the forest floor, D. rex may increase the likelihood that its spores travel farther and reach suitable locations for growth. Researchers will need to conduct additional studies to determine whether this explanation accounts for its unusual size or whether other biological and environmental factors are involved.
Why researchers still have so much to discover regarding fungi
The recognition of Dianjunus rex underscores a notable blind spot within scientific understanding. While experts have officially cataloged roughly 150,000 types of fungi, certain projections indicate that a staggering two million to 13 million distinct varieties could actually populate the globe.
The gap between these numbers demonstrates that a significant share of fungal biodiversity is still unrecorded. Numerous species dwell within hard-to-access habitats, whereas others prove difficult to recognize since their visible structures emerge exclusively under precise circumstances.
The vast majority of any fungus is composed of tiny, thread-shaped filaments known as hyphae. Collectively, they create a web called the mycelium, which generally develops beneath the ground, within rotting timber, or amid plant matter. Those reproductive forms that individuals identify as mushrooms, along with other visible fungal manifestations, merely constitute a fraction of the living entity.
These formations can develop when environmental conditions prove favorable or throughout specific phases of the fungal life cycle. Consequently, a substantial and conspicuous species like D. rex may easily elude detection for years.
Stanford’s Peay emphasized that cataloging fungal varieties serves as a crucial initial phase in grasping their ecological functions. Researchers first need to determine which organisms are present prior to exploring the ways those species engage with flora, fauna, and their environment.
Fungi contribute to the carbon cycle, break down organic matter and support the growth and nutrition of many plants. Understanding their diversity is therefore important not only for taxonomy and evolutionary biology but also for broader research into ecosystem health.
Ultimately, Dianjunus rex represents more than an unusually large fungus. Its discovery provides an opportunity to investigate how fungi evolve, why certain species develop exceptional physical characteristics and how environmental changes shape biodiversity over millions of years. It also serves as a reminder that even in ecosystems that have been explored for decades, nature can still reveal organisms that expand our understanding of life on Earth.
