Trifurcitus Brinck, 1945

Miller, Kelly B., Michat, Mariano C. & Ferreira Jr, Nelson, 2024, Reclassification of Cybistrinae Sharp, 1880 in the Neotropical Region (Coleoptera, Adephaga, Dytiscidae), with description of new taxa, ZooKeys 1188, pp. 125-168 : 125

Trifurcitus Brinck, 1945 stat. nov.

Figs 3 , 8 , 65 , 71

Trifurcitus Brinck, 1945: 8.

Type species.

Cybister fallax Aubé, 1838b: 54, by original designation.

Diagnosis.

These are former Megadytes species with the anterior metatibial spur apically trifid (Fig. 3 ). Specimens are very large for diving beetle species (TL = 27-36 mm). They are somewhat similar to Bifurcitus specimens. See under that genus for diagnostic comparisons. Larvae are distinctive in having the median lobe of the frontoclypeus sharp apically without an apical tuft of setae.

Phylogenetic relationships.

Trifurcitus is sister group to Bifurcitus (Figs 75 , 76 ). Both males and females have equal-length metatarsal claws and the anterior metatibial spur is either bifid (Figs 1 , 2 ) or trifid (Fig. 3 ), although these two conditions may possibly not be homologous.

Discussion.

See above under Bifurcitus for more discussion of these two taxa. Six species are currently recognized. Although they have not been revised thoroughly, most of the species were described or illustrated by Trémouilles (1989a) and Trémouilles and Bachmann (1980).

Other species

Figures

Figure 75. One of seven cladograms derived from parsimony analysis of 57 morphological characters from Cybistrinae and other Dytiscidae (len = 105, CI = 68, RI = 92) with characters mapped using ' fast' optimization in WinClada. Black hash marks indicate unambiguous changes, white hash marks indicate homoplasious changes or reversals. Numbers above hash marks are character numbers, those below hash marks are derived state numbers.

Figure 76. Consensus cladogram of seven equally parsimonious cladograms from parsimony analysis of 57 morphological characters from Cybistrinae and other Dytiscidae morphology.

Figures 1 - 8. Cybistrinae morphological features 1 Bifurcitus lherminieri, right metatibia, posterior surface 2 Bifurcitus lherminieri, left metaleg, anterior surface 3 Trifurcitus robustus, left metaleg, anterior surface 4 Metaxydytes fraternus, left mesotarsomeres III-V, posterior surfaces 5 Cybister tripunctatus, left mesotarsomeres III-V, posterior surfaces 6 Megadytes latus, left half of metaventrite and left metacoxa (WV = metaventrite wing width, WC = metacoxal width) 7 Cybister tripunctatus, right metathoracic wing 8 Trifurcitus robustus, right metatrochanter, ventral surface. Scale bars: 1.0 mm.

Figures 62 - 66. Neotropical Cybistrinae species, female genitalia including left gonocoxosternite, ventral aspect 62 Metaxydytes fraternus 63 Paramegadytes glaucus 64 Bifurcitus lherminieri 65 Trifurcitus robustus 66 Cybister fimbriolatus. Scale bars: 1.0 mm.

Figures 67 - 71. Third instar larva, anterior clypeal margin 67 Bifurcitus magnus 68 Megadytes latus 69 Metaxydytes carcharias 70 Paramegadytes glaucus 71 Trifurcitus fallax.