| Author||L. van der Hammen|
|Title||Notes on the morphology of Alycus roseus C. L . Koch|
|Abstract||Recently, in my second study on Opilioacarida (Van der Hammen, 1968b), I noted that it would be interesting to make a morphological comparison between Opilioacarus (as primitive representative of the Anactinotrichida) on the one hand, and one of the primitive Actinotrichida on the other. It appeared that a species of Alycus, viz., A. roseus C. L. Koch (1841), was excellently suited for this purpose. Because an extensive description of Opilioacarus texanus (Chamberlain & Mulaik) was already published by me (Van der Hammen, 1966), it sufficed to prepare a study of the Alycus species according to the same principles of observing, describing and drawing.|
Because the opisthosoma of Alycus roseus presents a distinct segmentation, and consists of the highest number of segments known from the superorder, a detailed description, moreover, appeared to be of considerable interest for a further study of soma terminology and segmentation in Actinotrichida.
Both reasons have given rise to the preparation of the present paper.
The generic name Alycus C. L. Koch (1841:19; 1842:38) has been placed by Grandjean (1936:398), Oudemans (1937:866), and Willmann (in: Sig Thor & Willmann, 1941:133) in the synonymy of Pachygnathus Dugès (1834:37). This synonymy, however, is not very convincing. Dugès (1834: 37, pl. 8 fig. 52) described and figured the type-species, Pachygnathus villosus Dugès, as presenting curved setae. This condition is not known from species now classified with the genus. Moreover, Dugès figured the idiosoma of the species as presenting a pronounced lateral constriction; this character is not present in A. roseus.
A redescription of Pachygnathus villosus after topotypic material is badly needed. However, the type-locality is not known, although it is supposed to
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