Baissalarva hydrobioides, 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 : 718-721

BAISSALARVA HYDROBIOIDES SP. NOV.

Type locality and age: Russia, Buryat Republic , Baissa. Early Cretaceous, Berriasian–Hauterivian, c. 146–135 Mya ( Zherikhin et al., 1998; D. V. Vassilenko, pers. comm to A.P., 2011) .

Type material (two specimens): Holotype: PIN 3063 / 6975, piece and counterpiece ( Figs 3D–F , 6A–C ) . Paratype: PIN 3063 /6977, piece only ( Figs 3C , 6D ) .

Description: Body length c. 10.0 mm, head width c. 1.2 mm; body elongate.

Head c. as long as wide, with large occipital foramen situated dorsally. Anterior margin with dentate nasale mesally, bearing five large teeth with the left one (seen on the right in the respective fossil) slightly more separated from remaining ones; anterolateral part with symmetrical, low arcuate epistomal lobes. Frontal lines weakly developed, converging towards posterior margin of head, coronal suture at most very short. Eyes present posterolaterally of epistomal lobes consisting of separate stemmata. Mandible long and falcate, with three inner teeth, two distal ones large, proximal one small. Submentum trapezoidal, narrowing anteriad, submental suture angulate medially, well developed. Gula reduced, gular sutures fused into a single median line. Cervical sclerites present, transverse.

Thorax. Pronotum completely sclerotized, proscutum subdivided by fine sagittal line. Mesonotum with one pair or large subtriangular transverse sclerites subdivided into darker anterior and paler posterior parts. Metanotum anteriorly with a pair of large transverse sclerites subdivided into anterior and posterior portion in the same way as on mesonotum. Posterior portion of metanotum with another pair of more weakly delimited and smaller sclerites.

Abdomen largely membranous, bearing only minute sclerites dorsally. Abdominal segments 1–7 each with two pairs of minute sclerites, anterior ones darker, ring-like, more distinctly delimited, posterior ones paler and more weakly delimited. Abdominal segment 8 with small dorsal plate. Internal portion of abdomen with two massive tracheal trunks, segments 1–7 without evident spiracles.

Etymology: The species name refers to the extant genus Hydrobius , a representative of the tribe Hydrobiusini to which Baissalarva belongs.

Figures

Figure 3. Early Cretaceous representatives of the Hydrobiusini. Cretoxenus australis gen. nov., sp. nov., Koonwarra, Australia, NMVP 103312, piece and counterpiece (A, B). Baissalarva hydrobioides gen. nov., sp. nov. from Baissa, Russia: paratype PIN 3063/6977 (C); holotype PIN 3063/6975: piece, detail of the head (D), counterpiece, detail of the head (E), whole specimen, counterpiece (F). Abbreviations: absc, abdominal dorsal sclerite; absc4, absc7, abdominal dorsal sclerite of segment 4 or 7; aes3, metanepisternum; apls, anapleural suture; cersc, cervical sclerite; dpl8, dorsal plate on abdominal segment 8; epl, epistomal lobe; md, mandible; men, mentum; mssc, mesoscutum; mstr1, mesotarsomere 1; msv, mesoventrite; mxp, maxillary palpus; mtsc, metascutum; ns, nasale; occf, occipital foramen; pros, prosternum; sbm, submentum; scsh, scutellar shield; sstr, sutural stria; ttr, tracheal trunk.

Figure 6. Fossil and recent representatives of the Hydrobiusini and Hydrophilini. Baissalarva hydrobioides sp. nov.: holotype PIN 3063/6975, anterior part of the piece (A), detail of the head of the piece (B), detail of the head of the counterpiece (C); paratype PIN 3063/6977 (D). Larva of extant Limnoxenus niger (Hydrobiusini): whole larva in dorsal view (E), detail of head (G). Larva of extant Sternolophus rufipes (Hydrophilini): whole larva in dorsal view (F), detail of head (H). Holotype of Cretoxenus australis sp. nov. NMVP 103312, piece and counterpiece (I, J). Extant hydrobiusine Limnoxenus zealandicus in ventral view, whole beetle (K) and detail of meso- and metaventrite (L). Abbreviations: md, mandible; mtvpr, metaventral process.