Phylum Nematoda: a classification, catalogue and index of valid genera, with a census of valid species.

A classification of the entire Phylum Nematoda is presented, based on current molecular, developmental and morphological evidence. The classification reflects the evolutionary relationships within the phylum, as well as significant areas of uncertainty, particularly related to the early evolution of nematodes. It includes 3 classes, 8 subclasses, 12 superorders, 32 orders, 53 suborders, 101 superfamilies, 276 families, 511 subfamilies, 3030 genera, and 28537 species. All valid species named from the time of publication of the previous classification and census (2010) to the end of 2019 are listed, along with the number of valid species in each genus. Taxonomic authorities are provided for taxon names of all ranks. The habitats where the species in each genus are found are listed, and an alphabetic index of genus names is provided. The systematics of nematodes is reviewed, along with a history of nematode classification; evolutionary affinities and origins of nematodes; and the current diagnosis of the group. Short overviews of the general biology, ecology, scientific and economic importance of the group are presented.