NAME Mycocarpon pachydermum
AGE Carboniferous.   AGE span: 359.2...299 mya
K&J CLASSIFICATION (2000) Ascomycetes, Eurotiales.
FIGURE(S)
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Pl.29fig.15.jpg
FIGURE REFERENCE Williamson WC. 1880. On the organization of the fossil plants of the Coal Measures.--Part X. Including an examination of the supposed radiolarians of the Carboniferous rocks; Philosophical Transactions of the Royal Society of London, v. 171, p. 493-539.
SPECIES, AUTHORITY M. pachydermum (Williamson) Hutchinson 1955, p. 426
LOCATION “Halifax Beds,” the more precise location of which apparently was given in the first instalment of Williamson’s monograph, in which he illustrated megaspores from the same beds. (Volcanic ash at Laggan Bay, Arran, Scotland?)
ORIG DESCRIPTION* "Two slides from Halifax, for which I am indebted to Mr. Spencer, contain clusters of conceptacles of a perfectly distinct type. Each conceptacle has a diameter of about .016 to .012. As seen in figs 35 and 36, their form is that of rounded spheres, having a very thick outer investing layer, a, and a delicate, structureless inner one, b. In fig. 35 this inner membrane is intersected through its centre, but in fig. 36 the section has passed through it tangentially, illustrating its spherical form. In the latter instance it contains a number of very minute granular bodies that look like spores. When examined under low powers, even with the quarter-inch objective, the outer layer, a, appears to be composed of a mass of small, irregular parenchymatous cells, but oil-immersion (one-eighth) revealed the structure shown in fig. 37. It consists of a dense mass of branching and interlacing tubes of varying diameters, the interstices of which appear to be filled up with a structureless substance. At numerous points, as at a, a, in the figure, the section has cut through these branches transversely. In other places, as at b, b, we have the meshes of the tubular network. In a few specimens I find two inner circular cavities of this form enclosed within a common peripheral tubular investing layer a; but there is usually but one, and their ordinarily detached condition and comparatively uniform contour suggests that they have been closely grouped but independent organisms, and not the broken up portions of a common mass. Figs. 35 and 36 are enlarged 162, and fig. 37 750 diameters."

EMENDED DESCRIPTION (Hutchinson 1955, p. 426): Spherical fossil fungal structures approximately 275 to 600 µm in diameter, each typically containing a single spherical cavity approximately 175 to 260 µm in diameter within a wall made up of septate hyphae. In some cases two cavities have a common wall in some part of their circumference. The wall is made up of an interwoven mass of branching hyphae which are approximately 5 to 20 µm in diameter, mostly 8 to 15 µm. Large oval cells approximately 40 to 70 by 25 to 110 µm in diameter may be present in the outer layers of the wall. The cavity may contain an apparently structureless membrane approximately 125 to 225 µm in diameter. A group of rounded cells with rough walls, 3 to 9 µm in diameter, or a group of thin-walled cells 20 to 50 µm in diameter, may lie irregularly within the membrane.
COMMENTS* (Williamson): What these objects are is not easy to determine. It is impossible to overlook the resemblance between the branching tubules of the outer investment and fungoid hyphae; but I know of no fungoid reproductive structures that in any way resemble them in their entirety.

(Hutchinson): This revised description is based upon a re-examination of Williamson's slides together with an examination of 23 specimens from the Kidston Collection, 17 specimens from the Departmental Collection in the University of Glasgow, and 50 specimens in a series of serial sections cut from a coal ball from the Werister Colliery, Liège, Belgium. The measurements of the specimen are given in Table I. [For details, refer to original paper.]
PUBLICATION REFERENCE Williamson WC. 1880. On the organization of the fossil plants of the Coal Measures.--Part X. Including an examination of the supposed radiolarians of the Carboniferous rocks; Philosophical Transactions of the Royal Society of London, v. 171, p. 493-539.

Hutchinson SA. 1955. A review of the Genus Sporocarpon Williamson; Annals of Botany, v. 19, p. 425-435.
K&J REMARKS
TYPE HOLOTYPE: Slide 1503, Williamson’s Collection, British Museum (Nat. Hist.).
ALL NAMES (Including synonyms) Sporocarpon pachydermum Williamson 1880, p. 510, pl. 17, figs. 35-36, pl. 18, fig. 37. ; Mycocarpon pachydermum
SERIAL NUMBER 1141
PUBLIC COMMENTS
 *For source, see Publication Reference.