NAME Sporocarpon compactum
AGE Carboniferous.   AGE span: 359.2...299 mya
K&J CLASSIFICATION (2000) Ascomycetes, Eurotiales.
FIGURE(S)
Image of
Pl.29fig.2.jpg
FIGURE REFERENCE Williamson WC. 1878. On the organization of fossil plants of the Coal Measures. Part IX; Philosophical Transactions of the Royal Society of London, v. 169, p. 319-364.
SPECIES, AUTHORITY S. compactum Williamson 1878, p. 348-349.
LOCATION England.
ORIG DESCRIPTION* "Fig. 76A, the original of which I am indebted to Mr. Binns, represents a sphere composed of a single layer of oblong cells, a, the inner ends of which are flattened and in close contact so as to bound a very regular and smooth internal, spherical cavity. These cells continue in close contact throughout the greater part of their length, but their peripheral extremities are free, and more or less rounded. The dark circle, b in the figure, represents a portion of this smooth inner bounding wall of the cavity which happens not to have been cut through, at either surface of the section, in the plane of its greatest diameter. At c, we have a collapsed inner and apparently structureless membrane apparently corresponding to d in fig. 67. At the first glance this conceptacle appears similar to that represented by figs. 75, 76. But this difference exists between the two: in the former the bounding wall of the conceptacular cavity consists of a single layer of cells, with perfectly free outer extremities. In the two latter, that boundary wall consists of at least a multi-cellular layer, whilst such examples as 75A, and 76 indicate that the entire structure has been embedded in and formed part of a parenchymatous structure. Such has certainly not been the case with the organism now under consideration. I have as yet discovered in the specimen of the latter, no trace of a peduncle, or point of attachment to any other structure. Fig. 76A, is enlarged 324 diameters."

EMENDED DESCRIPTION (Hutchinson 1955, p. 431): Spherical structures approximately 325 to 450 µm in diameter, each containing a single spherical cavity approximately 230 to 300 µm in diameter. The wall is made up of a single layer of oblong club-shaped cells, the inner ends of which are flattened and in close contact so as to bound a very regular cavity. These cells continue in close contact throughout their length. Their peripheral ends may be blunt, mamillate, or project as short hairs. The cavity may contain an apparently structureless membrane, and round or oval cells approximately 15 to 30 µm in diameter may be present either within the membrane or scattered irregularly throughout the cavity.
COMMENTS* (Hutchinson): This description is based on a re-examination of Williamson's slides, together with an examination of 15 other specimens from the Kidston Collection, one from the British Museum, and six from the departmental teaching collection at Glasgow University. The measurements of the undistorted specimens are given in Table IV [l.c.; for details, refer to the original paper].
PUBLICATION REFERENCE Williamson WC. 1878. On the organization of fossil plants of the Coal Measures. Part IX; Philosophical Transactions of the Royal Society of London, v. 169, p. 319-364.

Hutchinson SA. 1955. A review of the Genus Sporocarpon Williamson; Annals of Botany, v. 19, p. 425-435.
K&J REMARKS Williamson (1880) indicated, after studying new material of the species he described earlier (Williamson, 1878), that the specimens he described as the apparently different species Sporocarpon elegans and S. compactum, may be but different stages in the development of the same organism; the latter being the younger, and the former the more matured states. He also pointed out that the minute objects that he designated Oidospora, may be very young forms of the same, though he had no sufficient evidence to prove the validity of this surmise.

Hutchinson (1955) transferred Sporocarpon compactum to Dubiocarpon, as D. compactum (Williamson) Hutchinson 1955. However, he was not aware of McLean's work (1912, 1922) on these forms, and the latter's (1922) explicit designation of Sporocarpon compactum as type species of Sporocarpon. Thus, when Hutchinson unwittingly included S. compactum, type of the genus Sporocarpon, in the genus Dubiocarpon, he made Dubiocarpon nomenclaturally illegitimate and incorrect, as the older name Sporocarpon should be used for this taxon (ICBN, Art. 52.1).However, according to Art. 52.3, it appears possible to justify both generic names, by removing S. compactum from Dubiocarpon, thereby make the latter legitimate again.

Possibly, if Williamson's hunch that S. compactum and S. elegans are different maturity states of the same taxon were correct, the resulting taxonomic synonymy of Dubiocarpon and Sporocarpon would be a serendipitous outcome. However, Hutchinson (1955, p. 433), after having re-examined Williamson's slides, found no evidence of intermediate forms constituting a gradation between D. elegans and D. compactum, and thus no justification for merging these species. Stubblefield et al. (1983), by implication, also did not seem to support this notion, and described the specimen that Williamson considered to be intermediate between these two forms, as their new species Dubiocarpon ductilum.
TYPE S. compactum Williamson 1878, p. 348-349. Holotype: Slide 1514, Williamson Collection, British Museum of Natural History. [Hutchinson, 1955.]
ALL NAMES (Including synonyms) Sporocarpon compactum
SERIAL NUMBER 1608
PUBLIC COMMENTS
 *For source, see Publication Reference.