STUDIES OF CARBONIFEROUS FUNGI. II. THE STRUCTURE AND ORGANIZATION OF MYCOCARPON, SPOROCARPON, DUBIOCARPON, AND COLEOCARPON (ASCOMYCOTINA)

The problematic organism, Sporocarpon, was among the first fossil fungi to be described. The genus was actually a heterogeneous assemblage of fungal forms, and was eventually divided into several taxa including Sporocarpon, Dubiocarpon} and A{ycocarpon. In the present paper these organisms, as well as a similar, previously undescribed genus, Coleocarpon, are described from Lower Middle, and Upper Pennsylvanian strata in North America, and from Upper Carboniferous sediments in England. Although initially considered to be radiolarian-like protozoa, these structures show far more similarity to ascomycetous cleistothecia. All forms are ornamented, spherical bodies with a complex wall which encloses scattered asci and ascospores. Taxa are distinguished primarily by diffierences in the organization of the cleistothecial wall. Structurally similar organisms are found today among the Eurotiales. J7ossiles incertae sedis. This taxonomic organization has been consistently accepted to the present time (BaxterS 1960; Davis and Leisman, 1962; Tiffiney and Barghoorn, 1974). Fossil sporocarps were first reported from North America by Baxter (1960), who described Sporocarpon and Dubiocarpon from the Pennsylvanian of Kansas and Missouri. Shortly afterwards, Davis and Leisman (1962) described several species of Mycocarpon, Sporocarpon, and Dubiocarpon from the Middle Pennsylvanian of Kansas. These genera were not investigated further until Traquairia, a morphologically similar form, was described from several localities in the United States and Europe (Stubblefield and Taylor, 1983). Fungal sporocarps are far more abundant in North American coal ball floras than might be implied by their scarcity in paleobotanical literature. Recently, an investigation of North Amencan Traquairia has demonstrated its abundance and the value of scanning electron microscopy in documenting the structure of fossil cleistothecia (Stubblefield and Taylor, 1983). Further examination of North American coal balls has revealed representatives of Sporocarpons Dubiocarpons and Mycocarpon as well as an additionalS previously undescribed organism with a similar organization. In this paper representatives ofthese taxa from several North American coal ball localities are described and compared with their European IN THE LATE 1800 s, Williamson proposed the generic name Sporocarpon for several types of problematic microfossils from the Upper Carboniferous of England (Williamson, 1878 1880, 1883). Soon after the first of these, S. cellulosum, was described, Williamson proposed seven additional species: S. elegans, S. compactum, S. tabulatum (Williamson, 1878) S. pachyderma, S. asteroides, S. ornatum (Williamson, 1880), and S. anomalum (WilliamsonS 1883). At this point the genus was loosely defined and included a number of disparate forms. Although McLean (1912) recognized the heterogeneity ofthe assemblage, he chose only to divide the genus into five sections. Much later Hutchinson (1955) reexamined Williamson's original material and revised the genus retaining only S. cellulosum and S. asteroides in Sporocarpon, and erecting two new genera: Mycocarpon to include S. pachyderma, and Dubiocarpon to include S. compactum and S. tabulatum. He placed S. ornatum (which he regarded as a synonym of S. anomalum) in ' Received for publication 13 December 1982revision accepted 14 June 1983. The authors wish to thank Dr. Roland L. Seymour of The Ohio State University who generously participated in much thought-provoking discussion. We also appreciate the use of specimens loaned to us by Dr. Gilbert A. Leisman of Emporia State University and Dr. Gar W. Rothwell of Ohio University who loaned several of the specimens examined in this study.