Between the years 1940 and 1968 Schultz and Falkenbach published eight papers revising the taxonomy of oreodonts (Merycoidodontidae). Although these papers suffer from many difficulties, including the oversplitting of taxa and the citation of plastically deformed features as diagnostic characters (M. S. Stevens, personal commun.), they remain the primary systematic work on oreodonts produced this century.

While preparing materials for the pentameroid portion of the Treatise on Invertebrate Paleontology revision of the brachiopod volumes, problems were encountered with four enigmatic genera: Rugolepyros Lenz, 1989; Aenigmastrophia Boucot, 1971; Spondylostrophia Kulkov, 1967; and Stricklandistrophia Sapelnikov and Rukavishnikova, 1975.

Recently, aguirre urreta and Riccardi (1988) have shown that Calliscaphites andinus Leanza, 1970, belongs in Myloceras Spath, and raised Calliscaphites as a subgenus for crioceratid coiled members of this genus. In doing so, they noted (p. 611) that, although Whitehouse (1926) had previously described Aleteceras as a genus for crioceratid coiled species that are now (Wright, 1957) included in Myloceras, none of these species appeared to have been unequivocally shown to have a crioceratid mode of coiling throughout life. This view had been strengthened by their reading of McNamara (1978). They did, however, note that “crioceratid coiling in Aleteceras would imply validation of this taxon as a senior synonym of Calliscaphites.”