Protochares, Fikáček & Prokin & Yan & Yue & Wang & Ren & Beattie, 2014

Fikáček, Martin, Prokin, Alexander, Yan, Evgeny, Yue, Yanli, Wang, Bo, Ren, Dong & Beattie, Robert, 2014, Modern hydrophilid clades present and widespread in the Late Jurassic and Early Cretaceous (Coleoptera: Hydrophiloidea: Hydrophilidae), Zoological Journal of the Linnean Society 170 (4), pp. 710-734 : 714-715

PROTOCHARES GEN. NOV.

Type species: Protochares brevipalpis sp. nov. (by present designation).

Time range: Late Jurassic.

Diagnosis: Body medium-sized; body elongate oval; labrum well sclerotized and at least partly exposed; maxillary palpi rather short and stout; scutellar shield small, triangular; elytron with ten series; scutellar stria present; basal metatarsomere 1 much shorter than metatarsomere 2.

Etymology: The generic name consists of the Latin prefix proto - meaning ‘early’, and the ending -chares reflecting the superficial resemblance of the new genus to the extant genus Helochares . Masculine.

Family assignment: Protochares gen. nov. may be reliably assigned to the superfamily Hydrophiloidea by the large clypeus and distinct frontoclypeal sutures reaching the lateral margin of the head closely before eyes. The presence of the triangular scutellar shield excludes all hydrophiloid families except Hydrophilidae and Spercheidae (Fikáček et al., 2012b) ; from Spercheidae it differs in head not strongly constricted behind the eyes and the wellsclerotized and largely exposed labrum. It may be therefore reliably assigned to the Hydrophilidae s.s.

Comparison with other hydrophilid genera: Based on the combination of the first metatarsomere much shorter than the second and the exposed labrum, Protochares gen. nov. corresponds well with modern representatives of the non-sphaeridiine groups of the Hydrophilidae . Among these, its general habitus and medium body size resemble, in particular, the extant representatives of the tribes Hydrobiusini (from most of which it differs by smaller body size and rather short maxillary palpi), subfamily Enochrinae (in contrast to which it bears five segmented metatarsi and short maxillary palpi), Acidocerinae (from many of which it differs by short maxillary palpi) and Rygmodinae (from which it differs by the presence of the scutellar stria on the elytron). All four extant groups are characterized by a rather generalized body and lack of ‘easy-to-see’ synapomorphies (Short & Fikácˇek, 2013), which makes the diagnosis of Protochares gen. nov. rather difficult. Still, the combination of diagnostic characters listed above and the Jurassic age of the fossil justifies the assignment of the fossil to a separate genus.

Protochares differs from the Early Cretaceous hydrophilid genera described below by rather wide metanepisterna (in contrast to much narrower ones in Cretoxenus gen. nov.), relatively short maxillary palpi (in contrast to rather long ones in Cretoxenus gen. nov. and probably also in Alegorius gen. nov.) and by a probably not excised clypeus and partly exposed labrum (in contrast to excised clypeus in all Cretaceous genera and labrum situated in the clypeal excision in Hydroyixia gen. nov., see Fig. 8A, C, E ).

Figures

Figure 8. Reconstructions of the clypeus shape and meso- and metathoracic morphology of the Early Cretaceous hydrophilid genera known in adult stage (three-dimensional structure of the mesoventrite not reconstructed). Alegorius gen. nov. (A, B); Cretoxenus gen. nov. (C, D); Hydroyixia gen. nov. (E, F). Head and thorax of the respective genus not to scale.