Expanding Horizons in the Recognition of a Phylum

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Abstract
The historical development of taxonomic concepts in the Acanthocephala is traced. Recognized first by the early microscopists, specific names were applied by the early taxonomists who failed to recognize the spp. as comprising any natural group for they assigned them to various genera of tapeworms, flukes, round worms and other groups. The entire nomenclatorial history is post-Linnaean. Echinorhynchus (1776) was the first generic name generally accepted and came to be regarded as coextensive with the order Acanthocephala proposed by Rudolphi in 1808 as a division of the class Vermes of Linnaeus. Following many diverse claims for alignment with cestodes, gregarines, and nematodes, the Acanthocephala have finally been recognized as a distinct phylum. Intimately detailed studies by Hamann led to his recognition of 3 separate families (1892), each based on a single genus. Modern expansion of the system of classification has been chiefly the elevation of these 3 families to higher categories. Various trends and systems are discussed. A new system for the groupings within the phylum is proposed which involves the recognition of 2 classes and 4 orders. The term METACANTHOCEPHALA is proposed for a new class to contain the orders Palaeacan-thocephala and Archiacanthocephala originally proposed by Meyer (1931). The name Eoacanthocephala, originally proposed by Van Cleave (1936) as an order, is elevated to the rank of a class, with Gyracanthocephala and Neoacantho-cephala, originally regarded as suborders, elevated to full ordinal standing. A table showing morph. features characteristic of each of the orders is presented.
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