NAME Archephoma cycadeoidellae
AGE Late Cretaceous - Middle Turonian.   AGE span: 93.6...88.6 mya
K&J CLASSIFICATION (2000) Fungi Imperfecti, Sphaeropsidales.
FIGURE(S)
FIGURE REFERENCE
SPECIES, AUTHORITY A. cycadeoidellae Watanabe, Nishida & Kobayashi 1999, p. 438, figs. 2, 3.
LOCATION On bisexual cone of Cycadeoidella japonica Ogura, recovered from shales in the Middle Yezo Group, Kami-kinenbetsu River, Hokkaido, Japan.
ORIG DESCRIPTION* Pycnidium is 200-250 µm wide, 170-200 µm high, and contains numerous globose conidia (figs. 2.7, 3.9, 3.10). A large number of similar structures showing different sizes and composition of cells comprise a continuous sequence that possibly represents a range of developmental stages (figs. 2, 3). Figures 2.2 and 2.3 are regarded as early developmental stages where accumulating cells are forming early pycnidia. Cells near the pycnidium center are smaller than those of the mature pycnidial wall, which consists of two to three layers of thick-walled cells (fig. 2.4). These smaller cells may degenerate (fig. 2.5), and the cells forming the inner layer of the pycnidial wall probably transform to conidiogenous cells. Figure 2.6 shows a transitional stage where the pycnidium consists of aggregated cells to the right and numerous small conidia to the left. A mature pycnidium contains numerous conidia in a thin pycnidial wall that subsequently ruptures to release conidia (figs. 2.7. 3.8). Ampliform conidiogenous cells are located at the periphery of the central cavity (fig. 3.9, arrow) and may produce small conidia (fig. 3.10); conidia hyaline, globose, smooth, aseptate and 2.6-3 µm in diameter. [Slightly condensed from original.]
COMMENTS* Archephoma is designated here as a new genus because it is a fossil, although its general features fit modern Phoma; other features remain unknown. To date, some Phoma or Phoma-like fossils have been recorded. LePage et al (1994) identified Phoma in the Middle Eocene permineralized chert from Canada. The specimen has single-septate conidia, but conidiogenesis is not known. The fossil genus Phomites from the Paleocene of Paris (Fritel, 1910) represents pycnidia without conidia developed on a fungal colony. Archephoma is separated from Phomites by the presence of conidia. From the Eocene of India, various forms of aseptate, hyaline, and lunate conidia are described under the fossil genus Palaeophoma (Singhai, 1974). Extant morphs with such features are generally included in Selenophoma (Sutton, 1980, pp. 374-377).

Archephoma differs from any of the above fossils in having pycnidia producing globose and aseptate conidia. The possible pycnidial development in A. cycadeoidellae resembles that of modern Phoma richardiae Mercher (1913). Figure 2.6 shows a cell aggregation prior to cavity formation of A. cycadeoidellae. Judging from the stages of cavity formation known in extant species, the central small cells probably arose from cells accumulated by division, followed by autolysis of the central cells to form the central cavity. Kempton (1919) recognized several types of cavity formation in pycnidial development: lysigenous, schizogenous, or a combination of both.

Etymology: Specific epithet derives from generic name of host plant.
PUBLICATION REFERENCE
K&J REMARKS See remarks from Kalgutkar and Jansonius (2000) under Palaeodiplodites yezoensis. As the holotype is illustrated by 10 separate aspects that presumably all are part of the original gathering, as the photographs show a large amount of detailed cell structures that are difficult to represent in a diagram, and as the publication by Watanabe et al. reached them only in the last days before going to press, Kalgutkar and Jansonius (2000) were not able to provide a line drawing of the type of this species.
TYPE
ALL NAMES (Including synonyms) Archephoma cycadeoidellae
SERIAL NUMBER 50
PUBLIC COMMENTS
 *For source, see Publication Reference.