Revision of the Class Archiacanthocephala Meyer, 1931 (Phylum Acanthocephala), with Emphasis on Oligacanthorhynchidae Southwell et Macfie, 1925

Class Archiacanthocephala is modified to include Moniliformida ord. n. All genera in Oligacanthorhynchidae were studied and several changes in classification of the family are made. Nephridiacanthus Meyer, 1931; Hamanniella Travassos, 1915; Travassosia Meyer, 1931; and Echinopardalis Travassos, 1918, are considered to be junior synonyms of Oligacanthorhynchus Travassos, 1915. Prosthenorchis elegans (Diesing, 1851) Travassos, 1915, P. lemuri Machado, 1950, and P. fraterna (Baer, 1959) comb. n. are retained in Prosthenorchis Travassos, 1915: all other species previously assigned to this genus are distributed among Pachysentis Meyer, 1931, Oncicola Travassos, 1916, and Neoncicola gen. n. The new genus is proposed for 7 species similar to Oncicola but with 30 rather than 36 proboscis hooks. Keys are provided for the orders in class Archiacanthocephala, and the 8 genera in Oligacanthorhynchidae accepted as valid. Each genus is redefined and a list of species in each is provided. No family in the Acanthocephala has a more confused literature than Oligacanthorhynchidae Southwell et Macfie, 1925. This condition has resulted from a number of causes: vague descriptions of species and uncertain definitions of genera by early authors, incorrect interpretations of morphology by more recent authors, and the homogeneity of the species themselves. Consequently it is almost impossible to identify an oligacanthorhynchid to genus, even using the keys of Petrochenko (1958), Golvan (1962), and Yamaguti (1963). During the past 10 years I have accumulated a large series of specimens representing all of the genera in the family. Several collectors have contributed specimens for study, most notably Dr. John F. Schacher who generously gave me a large collection which he assembled in Lebanon from 1961 to 1963. Study of these collections has made it possible to revise the family on sound morphological lines, without resorting to the separation of genera on the basis of definitive hosts, as has been historically accepted (e.g., Oligacanthorhynchus from birds, Hamanniella from opossums and edentates, etc.). Despite my efforts, and the efforts of others, it remains impossible to identify most juvenile forms to genus. The monotonous similarity of proboscis armature between most genera and species forces the systematist to rely on adult Received for publication 15 July 1971. characters, such as location of testes and shape of trunk, features that are unresolved in juveniles. The practice of describing juveniles as new species within a given genus in this family should be avoided, for it only continues to confound an already confused classification. The lists of species following the diagnoses of g nera in this paper have, for the most part, been uncritically drawn from the literature with little consideration of possible synonyms within each list. However, each species poorly known or known from juveniles only appears with a question mark before it. My interest here has been to resolve problems at the levels of genus and above; this should simplify the task for others who wish to further consider the species in each genus. In addition to studying whole mounts, stained with Semichon's carmine, I employed microdissections and serial sectioning to resolve certain problems, such as structure and insertions of the muscles of the proboscis receptacles. The typically thick walls of the trunk and the sheer size of many species make studies of whole mounts less practical than with most other families of Acanthocephala. The practice of describing proboscis armature as forming spiral rows of hooks has been avoided in this paper. The difficulties of counting hooks by this technique outweigh any advantage of ease of description. Instead, I consider the hooks to be arranged in short, approximately longitudinal rows.