Perplexacara, Watts & Bradford & Cooper, 2021

Watts, C. H. S., Bradford, T. M. & Cooper, S. J. B., 2021, A new genus, Perplexacara, and new generic placements of species of Australian marsh beetles (Coleoptera: Scirtidae) based on morphology and molecular genetic data, Zootaxa 4927 (4), pp. 539-548 : 543-545

Perplexacara gen. nov.

Description. Length 3.0– 5.5mm. Eye normal size (small in P. latusmandibulara ); without well-marked subantennal groove or carina. Antenna with scape greatly enlarged, widely oval, compressed, upper edge sharp; antennomere 2 small, inserted at end of scape, antennomere 3 smaller, together equal to or shorter than antennomere 4; subgenal ridge without buttonhole; mandible with one small tooth near apex; anterolateral angles of pronotum square or projected forward, anterolateral angles of clypeus not projecting forward (except in P. latusmandibulara ); labial palpi forked (sensu Watts & Zwick 2019); pronotal process narrow between procoxae, expanding to a narrow diamondshape at apex; mesoventral notch absent or small and U-shaped; pilosity on ventrites uniform. Females winged, gonocoxites elongate, never strongly sclerotized.

Larvae not known.

Etymology. Latin perplexa – enigmatic, a reference to the enigmatic morphology of the three included species. Cara – a common Scirtidae genus ending for Australian Scirtidae . Gender feminine.

Type species. Prionocyphon macroflavidus Watts.

Notes. A group of three species previously placed in the genus Prionocyphon principally on their enlarged scape and small antennomeres 2 and 3. All three of these species were considered to be atypical Prionocyphon by Watts (2010) when describing them although all in different ways. Perplexacara latusmandibulara in particular has a large number of distinctive apomorphic character states ( Watts 2010).

Phylogenetic analysis of sequence data in Cooper et al. (2014) placed the three species now grouped together under Perplexacara as distinct from the other Australian Prionocyphon as well as from P. serricornis Müller , the type species of the genus. The current study strongly suggests that, despite their considerable morphological differences, they form a close phylogenetic relationship. These three species can be separated from the other Australian species currently placed in Prionocyphon by the lack of a buttonhole on the subgenal ridge, the homogeneity of the abdominal pilosity, and the absence of an endophallus, all characters found in many of the Australian species currently placed in Prionocyphon .

Clearly the relationship of European Prionocyphon serricornis to Perplexacara and the Australian species remaining in Prionocyphon , together with the other Prionocyphon- like species from Southeast Asia requires additional study ( Zwick 2016).

Although well separated genetically ( Fig.1 ) species of Perplexacara are morphologically close to Macrodascillus but can be separated from this genus by their smaller size, presence of only one small tooth on the mandible rather than one strong one with a roughened area behind it and a small, U’-shaped mesoventral notch.

Larvae unknown.

Notes. The genus is found in wet Eucalypt forest in Southeast Australia from northern New South Wales to southern Tasmania.

Included species. Perplexacara caementum ( Watts, 2010) , P. latusmandibulara ( Watts, 2010) , P. macroflavida ( Watts, 2010) .

Figures

FIGURE 1. Bayesian consensus tree based on partial cyctochrome c oxidase subunit I (COI) codon positions 1 and 2, partial elongation factor 1-alpha (EF1-α) and Topoisomerase 1 (TOP1), constructed using MrBayes. Numbers on the branches are posterior probabilities.