|Ascothoracida and the unity of Maxillopoda|
Grygier, M.J. (1983). Ascothoracida and the unity of Maxillopoda, in: Schram, F.R. (Ed.) Crustacean phylogeny. Crustacean Issues, 1: pp. 73-104
In: Schram, F.R. (Ed.) (1983). Crustacean phylogeny. Crustacean Issues, 1. A.A. Balkema: Rotterdam, The Netherlands. ISBN 90-6191-231-8. 372 pp., more
In: Schram, F.R. (Ed.) Crustacean Issues. Balkema/CRC Press/Taylor & Francis: Rotterdam. ISSN 0168-6356, more
The class Maxillopoda (= Copepodoidea) originally contained the subclasses Copepoda, Mystacocarida, Branchiura, Cirripedia (including Rhizocephala), and Ascothoracida. This paper tries to answer the important, but neglected, question of whether such a grouping (now also including Ostracoda, Hansen's Y-larvae, Basipodella harpacticola and Deoterthron dentatum, and Pentastomida) is a natural one. A literature review of the class is conducted.All the previously suggested diagnostic characters, and some new ones, are analysed from a cladistic standpoint, and a new diagnosis based on the defensible synapomorphies is proposed. Archicopepoda (= Euthycarcinoidea) is excluded from the class, and doubts about the maxillopodan affinities of Bradoriida (including Phosphatocopina) are expressed. The (non-parasitic ancestor of the ascothoracids could have served equally well as the progenitor of all the maxillopodan taxa (i.e. the urmaxillopodan); the modifications necessary to derive each from it are detailed. Because of the extent of convergence among the component taxa, only a partially resolved cladogram of the class is proposed. Conventional notions about the relationships among maxillopodan taxa (e.g. a Copepoda-Branchiura-Mystacocarida clade) are not supported. There is some justification for formal taxonomic recognition of the class Maxillopoda, but it does not have as solid a foundation as the other crustacean classes.