New familial assignment for two harvestmen species of the infraorder Grassatores (Arachnida: Opiliones: Laniatores)

Abstract

Incorporating masculine genitalic characters into Opiliones taxonomy has produced important revisions in the systematics of this group of arachnids. Currently, the inclusion of penis morphology in the description of any taxon of Phalangida (harvestmen with penis: Eupnoi + Dyspnoi + Laniatores, as used in Pinto-da-Rocha et al. 2007) has become an almost “mandatory” standard (e.g. Acosta et al. 2007), and opilionologists have been working to establish the masculine genital pattern for each family (e.g., Martens 1986; subchapters in Pinto-da-Rocha & Giribet 2007). Still, in the infraorder Grassatores the diversity in penis morphology is enormous and much structure and functionality remains poorly understood. Unfortunately, for many of the described Grassatores, the genitalia are entirely unknown, and this constitutes an important impediment to reliable familial assignation (e.g., in Kury 2003, 41 genera were considered as incertae sedis). This problem is quite relevant to “phalangodid-like” genera, considering their rather homogeneous external appearance but highly diverse genitalia (Martens 1988). One of the most illustrative examples is the subfamily Tricommatinae Roewer, 1912, that has been originally described under Phalangodidae, but which has a male genitalia groundplan matching the Gonyleptoidea, a very distant superfamily (Giribet et al. 2010). Consequently it was raised to a separate family, closer to the Gonyleptidae than to the Phalangodidae (Kury 1992), and finally regarded as a member of Gonyleptidae (Kury 2003).