Following the extinction of the dinosaurs roughly 66 million years ago, alternative biological organisms adjusted to an evolving globe. A massive mushroom recently discovered in China is providing researchers with fresh perspectives regarding fungal development and the extraordinary biodiversity that still remains unmapped.
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.
On September 28, the results appeared in the academic journal Frontiers in Fungal Biology. Aside from presenting a previously undocumented species, the study uncovers a brand-new family of fungi, providing insights into the evolutionary paths and environmental adaptations of these organisms.
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
Another significant focus of the research involves the evolutionary roots of Dianjunaceae, the recently classified family comprising Dianjunus rex. Through genetic material analysis and cross-referencing the fungus with kindred organisms, researchers calculated that this family originated roughly one million years subsequent to the asteroid strike that concluded the Cretaceous Period.
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 surplus of dead organic matter could have additionally generated prospects for decomposers. Fungi are crucial in decomposing dead flora and fauna, recycling nutrients back into the habitat and sustaining the ongoing operation 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 reported that some local people had even tasted the fungus without experiencing noticeable adverse effects. However, the researchers have not conducted sufficient toxicity testing to establish whether it is safe to eat. The absence of reported symptoms should therefore not be interpreted as evidence that the species is edible.
This finding has additionally sparked inquiries concerning the reasons behind the substantial growth of reproductive organs in D. rex. Typically, ascomycetes refrain from generating massive stromata, a tendency likely linked to the substantial metabolic cost required for their construction and upkeep.
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 identification of Dianjunus rex highlights a significant gap in scientific knowledge. Researchers have formally described approximately 150,000 fungal species, but some estimates suggest that between two million and 13 million species may exist worldwide.
The difference between these figures indicates that a substantial portion of fungal biodiversity remains undocumented. Many species inhabit difficult-to-reach environments, while others are challenging to identify because their visible structures appear only under specific conditions.
Most of a fungus consists of microscopic, threadlike filaments called hyphae. Together, these form a network known as the mycelium, which typically grows inside soil, decaying wood or vegetation. The reproductive structures that people recognize as mushrooms or other visible fungal growths represent only part of the organism.
These structures may emerge when environmental conditions are favorable or during particular stages of the fungus’s life cycle. As a result, even a large and distinctive species such as D. rex can remain unnoticed for years.
Stanford’s Peay stressed that documenting fungal species is an essential first step toward understanding their ecological roles. Scientists must first establish which organisms exist before they can investigate how those species interact with plants, animals and their surroundings.
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.
