A taxonomic revision of the family Oncopodidae I. New genera and new species of Gnomulus Thorell (Opiliones, Laniatores)

The genera Oncopus Thorell, 1876 and Gnomulus Thorell, 1890 are rediagnosed; Pelitnus Thorell, 1891 is synonymised with Gnomulus because of intermediate forms and identical penis structure. Seventeen species described under Pelitnus are transferred to Gnomulus; generic placement in six of them (known only from females or juveniles) is provisional. Taxonomic characters of Oncopodidae and relationships within the Oncopodidae and with other families are discussed. Pelitnus thorelli Schwendinger, 1992 is a primary homonym; the species unduely described under this name is transferred to Gnomulus and renamed G. baharu Schwendinger nom. n. Three new genera and thirteen new species of mostly small oncopodid opilionids are described. Palaeoncopus gen. n., with P. gunung sp. n., P. kerdil sp. n., P. katik sp. n. from Sumatra possess a short, distad-directed, non-expandable glans penis, which is considered plesiomorphic. Biantoncopus gen. n., with B. fuscus sp. n. from the Philippines, has a similar but expandable glans. This character is regarded as apomorphic. Seven new species are placed in Gnomulus, i. e. G. crucifer sp. n.. G. maculatus sp. n., G. coniceps sp, n., G. leyteensis sp. n., G. laruticus sp. n., G. asli sp. n. and G. hirsutus sp. n. Their penis morphology, with a short proximad-directed glans, is typical for most Oncopodidae (also present in Oncopus) and is considered derived from the Palaeoncopus-type. Caenoncopus gen. n., including C. tenuis sp. n., C. affinis sp. n. and C. cuspidatus (Schwendinger) comb. n. (transferred from Oncopus) from Sumatra, has a glans penis comprising a strongly elongated, proximad-directed stylus wrapped in a membraneous collar. This structure appears highly apomorphic and is possibly an extreme modification of the penis type in Gnomulus and Oncopus. Intermediate states of reduction of glans sclerites and enlargement of stylus are present in G. crucifer sp. n. and G. maculatus sp. n., though they probably belong to a different evolutionary lineage. Four penis types are distinguished for the Oncopodidae; their evolution, generic significance and functional morphology are discussed.