Organism · Fungi
Archaeomarasmius leggetti
Source time context (not species duration) · ≈ 143–66 Ma
Inferred life reconstruction
Archaeomarasmius leggetti
Overview
Archaeomarasmius leggetti is a mushroom preserved in Cretaceous amber. A fruiting body with a small cap attached to a stalk conveys the form of an ancient mushroom. It introduces a kind of fossil different from bones or hard shells.[1]
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Key facts
One cap survives still attached to its stalk. The researchers described this fruiting body separately from a detached cap fragment. The fossil records even which parts of the small mushroom remained connected.[1]
Time and place
It is a Cretaceous amber fossil known from present-day New Jersey, USA. The Cretaceous spanned approximately 140–66 million years ago. The amber provides evidence that mushrooms with caps and stalks existed long ago.[1][2]
The time range describes source context, not the complete duration of this species.
Size, form and skeleton
An intact cap and its attached stalk are important features of this fossil. The material studied alongside it also includes a separate cap fragment. The cap-and-stalk structure that we picture as a mushroom is called a fruiting body.[1]
The caps of the two mushroom specimens preserved in amber measure approximately 3.2 mm and 6 mm in diameter. These are widths of the caps spreading like tiny umbrellas, not heights including the stalks.[8]
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Habitat and reproduction
This organism’s story begins with the form in which its small fruiting body survived. A fossil with the cap attached to the stalk shows the mushroom’s arrangement together. Comparing it with material preserving only a cap fragment highlights the value of connected preservation.[1]
Fossil discovery
A 1997 study examined mushroom fossils in both Miocene and Cretaceous amber. Archaeomarasmius was the Cretaceous material among them. Mushroom fossils from different times contributed to research comparing ancient fungal forms.[1]
References
- 1997 study — A Cretaceous mushroom in amber
- International Commission on Stratigraphy (2024) — Geological time chart
- Heads et al. (2017) — A Cretaceous mushroom with preserved cap and gills
- International Commission on Stratigraphy (2024) — Geological time chart
- 2018 correction — The naming record of Gondwanagaricites
- 1997 study — A Cretaceous mushroom in amber
- International Commission on Stratigraphy (2024) — Geological time chart
- Hibbett·Grimaldi·Donoghue (1997) — Fossil mushrooms in amber
Research questions
How might ancient mushrooms resemble living ones? Comparison can begin with the connection between cap and stalk in amber. The preservation of a small fruiting body leads to larger questions about fungal form and evolution.[1]
Observation
Move your gaze from the rounded outline of the cap to the slender stalk. Picturing the small fruiting body with these two parts connected, alongside the separate cap fragment, helps explain the structure preserved by the fossils.[1]
Related organisms
Gondwanagaricites magnificusFungiSource time context (not species duration) · ≈ 143–66 MaTwo ways Cretaceous mushrooms were preserved
Gondwanagaricites from present-day Brazil survived through mineral replacement in limestone, while Archaeomarasmius from New Jersey, USA, was preserved in amber. The 2017 paper noted that all other fossil mushrooms known up to that time had come from amber. Comparing Cretaceous mushrooms from different regions introduces several ways that small caps and stalks can become fossils.