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Abstract:
A new species of Cyrtodesmidae is described from a terra firme tropical rainforest patch near Manaus,
Central Amazonia of Brazil: Agnurodesmus siolii n.sp. Being the first formal record of a cyrtodesmid in
Brazil, this species, named after Prof. Dr. Harald SIOLI, seems to be particularly closely related to
Cliodesmus cryptopygus CHAMBERLIN, 1923, from Guyana, the type-species of Cliodesmus CHAMBERLIN, 1923, a genus hitherto treated of unclear status. The new species differs by the incomplete ozopore
formula (5, 15-18 versus normal), more numerous (5-6 versus 3-4) crenulations at the lateral edge of
paraterga 3 and 4, and certain details of gonopod structure, but otherwise the long established synonymy
of Cliodesmus under Agnurodesmus SILVESTRI, 1910 is supported. The entire family Cyrtodesmidae is
redefined, especially versus its counterpart family Pyrgodesmidae in the superfamily Pyrgodesmoidea, with
new diagnoses provided for all three currently accepted cyrtodesmid genera: Oncodesmella KRAUS, 1959
(two species, including O. pastazia (KRAUS, 1960), comb.n. ex Agnurodesmus), Cyrtodesmus COOK,
1896 (about 25 species), and Agnurodesmus SILVESTRI, 1910 (four species, all keyed). The distribution
pattern of Cyrtodesmidae being highly coherent, confined to northern South America, Tobago, and Central
America up to Costa Rica in the north, this family represents another example of the rather numerous
groups of Neotropical Diplopoda that managed to cross northward, however modestly, the Panamanian
portal known to have been closed since the Pliocene. The Seychellean genus Hyperothrix ATTEMS, 1900
is formally returned back from Cyrtodesmidae to Pyrgodesmidae not only on morphological but also
zoogeographical grounds.
