PHYLOGENY AND A REVISED CLASSIFICATION OF THE MONOGENOIDEA BYCHOWSKY, 1937 (PLATYHELMINTHES)

A hypothesis (CI = 57.3%) on the evolutionary relationships of families comprising the class Monogenoidea is proposed based on 141 character states in 47 homologous series and employing phylogenetic systematics. Based on the analysis, three subclasses, the Polyonchoinea, Polystomatoinea and Oligonchoinea, are recognised. The analysis supports independent origins of the Montchadskyellidae within the Polyonchoinea and of the Neodactylodiscidae and Amphibdellatidae within the order Dactylogyridea (Polyonchoinea); the suborder Montchadskyellinea is raised to ordinal status and new suborders Neodactylodiscinea and Amphibdellatinea are proposed to reflect these origins. The Gyrodactylidea (Polyonchoinea) is supported by three synapomorphies and comprises the Gyrodactylidae, Anoplodiscidae, Tetraonchoididae and Bothitrematidae. The analysis supports recognition of the Polystomatoinea comprising Polystomatidae and Sphyranuridae. Evolutionary relationships within the Oligonchoinea indicate independent origins of three ordinal taxa, the Chimaericolidea (monotypic), Diclybothriidea (including Diclybothriidae and Hexabothriidae) and Mazocraeidea (with five suborders). The suborder Mazocraeinea comprises the Plectanocotylidae, Mazocraeidae and Mazoplectidae, and is characterised by two synapomorphies. The suborder Gastrocotylinea, characterised by presence of accessory sclerites in the haptoral sucker, is divided into two infraorders, the monotypic Anthocotylina infraorder novum and Gastrocotylina. Two superfamilies of the Gastrocotylina are recognised, the Protomicrocotyloidea and Gastrocotyloidea; the Pseudodiclidophoridae is considered incertae sedis within the Gastrocotylina. The suborder Discocotylinea comprises the Discocotylidae, Octomacridae and Diplozoidae and is supported by four synapomorphies. The monotypic Hexostomatinea suborder novum is proposed to reflect an independent origin of the Hexostomatidae within the Mazocraeidea. The terminal suborder Microcotylinea comprises four superfamilies, the Microcotyloidea, Allopyragraphoroidea, Diclidophoroidea and Pyragraphoroidea. The analysis supports incorporation of the Pterinotrematidae in the Pyragraphoroidea and rejection of the monotypic order Pterinotrematidea. The following taxa are also rejected for reasons of paraphyly and/or polyphyly: Articulonchoinea, Bothriocotylea, Eucotylea, Monoaxonematidea, Tetraonchidea, Gotocotyloidea, Anchorophoridae and Macrovalvitrematidae. The Sundanonchidae, Iagotrematidae and Microbothriidae were not included in the analysis because of lack of pertinent information regarding character states.