The Relationships of the Nematode Superfamily Seuratoidea

Abstract

Echinonema cinctum is redescribed and referred to the Superfamily Seuratoidea: Seuratinema brevicaudatum is redescribed and the genus Seuratinema is provisionally accepted.2. The structure of the head in several species of the Seuratoidea is described and it is shown that the mouth opening is bilaterally symmetrical in Seuratinema and Seuratum.3. After a discussion on the developmental origins of the nematode head it is pointed out that all the labial structures in the Camallanidae and the Spiruroidea arise from a region of secondary elongation, i.e. from a cheilostome, while the paired jaws in the Cucullanidae arise as a modification of the oesophagus, i.e. are an oesophastome. As a consequence the family Cucullanidae is referred to the Seuratoidea : Ascaridida while the Camallanidae are left in the Spirurida.