Byssonectria terrestris (Alb. & Schwein.) Pfister

Phylum: Ascomycota - Class: Pezizomycetes - Order: Pezizales - Family: Pyronemataceae

Byssonectria terrestris

The genus Byssonectria comprises a group of simple disc-like ascomycetes with small fruitbodies and clavate asci. In many of the species each ascus contains eight ascospores, but there are some related species whose asci produce more than 2000 spores. Mostly these little fungi grow on various kinds of dung or rotting vegetation, often on disturbed soil beside woodland paths. Byssonectria terrestris is fairly typical of the genus, producing small orange disc-like fruitbodies


An extremely rare find in Britain and Ireland, Byssonectria terrestris occurs also throughout most of western Europe, from Scandinavia (where it is a relatively common sight on deer droppings) right down to northern Spain. There are references to this species occurring in Russia and also in Canada.

Byssonectria terrestris, Hampshire

Taxonomic history

In 1805 this ascomycete fungus was described by German mycologist Johannes Baptista von Albertini (1769-1831) and German-American Lewis David von Schweinitz (1780-1834); they gave it the scientific name Thelebolus terrestris. The currently accepted scientific name Byssonectria terrestris dates from a 1994 publication in Mycologia by American mycologist Donald H Pfister.

Synonyms of Byssonectria terrestris include Thelebolus terrestris Alb. and Schwein and Sphaerobolus terrestris (Alb. & Schwein.) W.G. Sm.


The specific epithet terrestris which means of the earth or the soil, and this ascomycete does indeed grow on soil.

Identification guide

Byssonectria terrestris, closeup

Ascocarp (fruitbody)

These bright yellow to orange fungi start off as tiny spheres and develop into bowl-shaped fruitbodies, typically up to 3mm across but exceptionally to 5mm. They have smooth hymenial or spore-producing upper surfaces, while the infertile (outer edge of the cup-shaped fruitbodies) surface is slightly paler and scurfy.

The short-stemmed cups are initially round but develop irregular margins where they push up against other fruitbodies.

Asci and spores of Byssonectria terrestris


185-200 x 10-13µm, with eight spores per ascus.


Narrow, curled at tips.

Paraphyses are structures of sterile tissue between the asci on the hymenial surface.

Show larger image

Spores of Byssonectria terrestris


Fusiform (spindle shaped) and smooth with rounded ends, 20-27 x 8-10μm; with two large oil drops and often several smaller drops

Spore print



Not distinctive.

Habitat & Ecological role

Saprobic, on well-rotted deer droppings among plant debris, often beside disturbed paths; this species has also been found growing on burnt conifer wood. It is reported to favour high nitrogen levels and a high pH.


Unclear as so few collections have been recorded, but related species can be found all year round but particularly in springtime.

Similar species

Several other ascomycetous disc fungi also colonise animal dung. Few can be identified from macroscopic features alone, and so microscopic examination of asci, spores and other cell structures is usually necessary.

Byssonectria terrestris, Hampshire, UK

Culinary Notes

Toxicity uncertain, but these cup fungi are far too small to be of any culinary interest.

Reference Sources

Dennis, R.W.G. (1981). British Ascomycetes; Lubrecht & Cramer; ISBN: 3768205525.

Breitenbach, J. & Kränzlin, F. (1984). Fungi of Switzerland. Volume 1: Ascomycetes. Verlag Mykologia: Luzern, Switzerland.

Medardi, G. (2006). Ascomiceti d'Italia. Centro Studi Micologici: Trento.

Dictionary of the Fungi; Paul M. Kirk, Paul F. Cannon, David W. Minter and J. A. Stalpers; CABI, 2008

Taxonomic history and synonym information on these pages is drawn from many sources but in particular from the British Mycological Society's GB Checklist of Fungi.


This page includes pictures kindly contributed by David Kelly.

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