Bifurcitus Brinck, 1945 stat. nov.

Figs 1, 2, 64, 67

Bifurcitus Brinck, 1945: 8.

Type species.

Cybister giganteus Laporte, 1835: 99 by original designation (= Dytiscus lherminieri Guérin-Méneville, 1829).

Diagnosis.

Within Cybistrinae Bifurcitus have (1) the lateral margins of the pronotum and elytra margined with yellow, (2) males and females each with two equal-length metatarsal claws, and (3) the posterior metatibial spur bifid (Figs 1, 2). These are the largest of all diving beetles with adult specimens 36-47 mm in total length (Hendrich et al. 2019). Third instar larvae have (1) the median lobe of the frontoclypeus truncate apically with a tuft of setae (Fig. 67), (2) the median and lateral lobes of the frontoclypeus separated by a wide emargination (Fig. 67), (3) the lateral lobes of the frontoclypeus apically simple (Fig. 67), (4) the lateral lobes of the frontoclypeus obtusely angulate (Fig. 67), and (5) the cephalic capsule relatively short (head length / head width <1.20).

Phylogenetic relationships.

Bifurcitus is sister group to the similar Trifurcitus (Figs 75, 76; Miller et al. 2007). Both have males and females with equal-length metatarsal claws and the anterior metatibial spur either bifid or trifid (although these two conditions may not be homologous) (Figs 1-3).

Discussion.

Although previous evidence suggested that the several subgenera of " Megadytes " are monophyletic, monophyly of this group is not supported here based in part on the discovery of undescribed cybistrine species with unique combinations of character states (Figs 75, 76). Given the situation, it seems appropriate to recognize these subgenera at the genus rank including Bifurcitus .

There are three currently valid species in Bifurcitus which were differentiated and characterized recently by Hendrich et al. (2019).