Microscydmus

Jałoszyński, Paweł, 2014, The smallest Cyrtoscydmini of Australia: revision of Microscydmus Saulcy & Croissandeau and Penicillidmus gen. n. (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 3774 (1), pp. 1-30 : 5-6

Subgenera of Microscydmus

Microscydmus is currently divided into five subgenera: cosmopolitan Microscydmus s. str. with nearly 170 species, Nearctic Delius Casey, 1897 (one species), Nearctic Neladius Casey, 1897 (one species), Neotropical Neoscydmus Franz, 1980 (nine species) and Oriental Parastenichnus (two species). Delius , Neladius and Parastenichnus were originally established as separate genera. Delius was reduced to subgenus of Microscydmus by Franz (1985), Neladius synonymized with Delius by Franz (1985) but resurrected as a subgenus by O'Keefe (1998), and Parastenichnus was reduced to a subgenus of Microscydmus by Jałoszyński (2005). All these subgenera require a comprehensive revision based on detailed morphological study; only structures of Parastenichnus were described in some detail, but since that time many novel characters were discovered in Cyrtoscydmini and descriptions have become much more detailed. Moreover, some extremely small Microscydmus -like Neotropical genera were recently revised ( Jałoszyński 2013a), revealing that fine structural details may be highly important for generic diagnoses. For this reason even the relatively well known Microscydmus (Parastenichnus) with only two previously revised species ( Jałoszyński 2005) requires more detailed study.

Independent of the taxonomic status (separate genus or subgenus of Microscydmus ), Delius , Neladius , Neoscydmus and Parastenichnus clearly differ from Microscydmus s. str. in the mesoscutellum (or mesoscutum indistinguishably fused with mesoscutellum, as commonly found in such tiny cyrtoscydmines, e.g. Jałoszyński (2013a)) visible between the elytral bases in intact specimens. In Microscydmus s. str. the mesoscutellum is externally not visible. Other differential characters for Delius and Neoscydmus are not clear; in Neladius "the pronotum is not impressed near the posterior margin" ( O'Keefe 1998) in contrast to distinct pits and sometimes transverse grooves present in the remaining subgenera, and Parastenichnus has unique long metaventral carinae extending postero-mesally from posterior margin of each mesocoxal process ( Jałoszyński 2005).