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ABSTRACT

Archaediscacean foraminifers (Archaediscidae and Asteroarchaediscidae) are excellent biostratigraphic markers found worldwide in Lower and Middle Carboniferous shelf carbonates. Their utility, however, is compromised because the morphology of many species is not clearly understood due to inadequate original descriptions and illustrations or to subsequent misuse of names in the literature. This report reevaluates type specimens previously described in 16 Soviet* and British papers representing many of the early taxonomic works on the group. The first author (PLB) examined and photographed most specimens on-site during a United States National Academy of Sciences exchange visit in 1984. Proposed nomenclatural changes include designation of lectotypes for Archaediscus karreri Brady, 1873, and Trochammina robertsoni Brady, 1876, and a new species name, aliminimus, for Archaediscus minimus Grozdilova and Lebedeva, 1953, a primary homonym of A. timanicus minimus Reitlinger, 1950.

Owing to their small size and preservation in limestone, archaediscaceans are usually examined in unoriented, whole-rock thin sections. This method of study presents problems for identification in that the thin section expression of internal coiling patterns depends not only on morphology but also on orientation. Because the influence of orientation has generally been overlooked, many seemingly discrete coiling patterns and, hence, species described in the literature are probably synonymous. To deal with this problem, the second author (CJG) developed a computer program to construct and “thin section” three-dimensional models of selected archaediscacean coiling patterns. The results provided valuable insights for distinguishing morphologic changes from artifacts of orientation and greatly influenced interpretation of the Soviet and British type specimens.

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