Batriscydmaenus, PARKER AND OWENS, 2018

Parker, Joseph & Owens, Brittany, 2018, Batriscydmaenus Parker and Owens, New Genus, and Convergent Evolution of a “ Reductive ” Ecomorph in Socially Symbiotic Pselaphinae (Coleoptera: Staphylinidae), The Coleopterists Bulletin 72 (2), pp. 219-229 : 224-225

Phylogenetic Position of Batriscydmaenus . Our initial impression of Batriscydmaenus was of a new and highly unusual genus, almost scydmaenine-like in form, but with shortened elytra and threesegmented tarsi that suggested a placement in Pselaphinae . The new taxon appeared to be highly atypical for a pselaphine, however, with several remarkable character states that are otherwise invariant within the subfamily. The overtly simplified morphology, with profound losses of foveae, sulci, and other characters used routinely for tribal placement, meant that unambiguous external characters to link the new genus to a higher taxonomic group were not forthcoming. One character—the apically notched antennal scape—suggested possible membership in the supertribe Batrisitae , but the approximation of this character state elsewhere in Pselaphinae ( Kurbatov 2007) prevented unequivocal placement. Batrisites possess a modified metaventrite margin that is curved at the midline to form a preapical fovea ( Chandler 2001), and we noticed that Batriscydmaenus has this feature. Furthermore, upon dissection we discovered the genus possesses four setae on the labrum—a proposed autapomorphy of Batrisitae ( Kurbatov 2007) . Still, the radical departure from the typical pselaphine (and batrisine) habitus was perplexing.

To circumvent the challenge posed by the morphology of the new genus to a definitive tribal placement, we assessed the phylogenetic position of Batriscydmaenus molecularly. We recovered fragments of nuclear 28s rRNA and mitochondrial 16s rRNA and COI from one of the paratypes. Bayesian analysis revealed that Batriscydmaenus emerges within a maximally supported Batrisitae clade ( Fig. 4 ). These results establish with confidence that the new taxon is indeed a morphologically derived member of Batrisitae . Our tree includes nine members of Batrisini as well as Arianops Brendel , a Nearctic member of the troglobitic batrisite tribe Amauropini . The position of Arianops within a clade otherwise composed of Batrisini genera indicates that Amauropini should be synonymized with Batrisini , as suggested previously ( Parker 2016b). We refrain from doing so until a greater range of amauropine genera can be sampled, but nevertheless conclude that Batriscydmaenus belongs within Batrisini rather than Amauropini . Notably, batrisines have undergone explosive genus-level diversification in the African and, in particular, the East Asian tropics, but up to now only six genera have been recorded from the Neotropics: Arthmius LeConte , Batoctenus Sharp , Iteticus Raffray , Oxarthrius Reitter , Syrbatus Reitter , and Syrmocerus Raffray ( Park 1942) . Batriscydmaenus thus represents the seventh Neotropical batrisine genus. In our tree, Batriscydmaenus is resolved as sister to the Neotropical genus Oxarthrius , but limited gene and taxon sampling precludes a more exact placement within Batrisini with any confidence.

Figures

Fig. 4. Bayesian consensus tree showing phylogenetic position of Batriscydmaenus within Batrisitae. Numbers above branches are posterior probabilities.