On the placement of the Baltic amber harvestmanGonyleptes nemastomoides Koch & Berendt, 1854, with notes on the phylogeny of Cladonychiidae (Opiliones, Laniatores, Travunioidea)

Abstract

The Baltic amber (Palaeogene: Eocene) harvestman Gonyleptes nemastomoides Koch & Berendt, 1854 (Arachnida: Opiliones), currently misplaced at both the genus and family level, is transferred to the extant family Cladonychiidae and assigned to a new genus, Proholoscotolemon n. gen. The families Gonyleptidae and Phalangodidae are hereby removed from the known harvest-man fossil record. Although the type specimen of G. nemastomoides is poorly preserved, the form of the diagnostic hind tarsal claw is clearly visible and indicates that the genus is distinct from, and relatively basal to, the only extant European cladonychiid genus, Holoscotolemon Roewer, 1915. Analysis of the claw morphology of extant cladonychiids, using evidence from ontogeny and outgroup comparison, suggests a transformation series in which the plesiomorphic condition (present in the eastern Nearctic genera Erebomaster Cope, 1872 and Theromaster Briggs, 1969) is a multi-pronged, narrowly forked claw with a long base, while the apomorphic condition (found in Holoscotolemon) is a bipronged, widely forked claw with a short base.