Helophorus (Mesosperchus) yixianus, Fikáček & Prokin & Angus & Pono & Marenko & Yue & Ren & Prokop, 2012

Fikáček, Martin, Prokin, Alexander, Angus, Robert B., Pono, Alexander, Marenko, Yue, Yanli, Ren, Dong & Prokop, Jakub, 2012, Revision of Mesozoic fossils of the helophorid lineage of the superfamily Hydrophiloidea (Coleoptera: Polyphaga), Acta Entomologica Musei Nationalis Pragae 52 (1), pp. 89-127 : 108

† Helophorus (Mesosperchus) yixianus sp. nov.

( Fig. 28 , 85–86)

Hydrophilopsia shatrovskiyi (paratype CNU 2010004, misidentification): PROKIN et al. (2010: 178)

Type locality and age. China, Liaoning Province, Shangyuan County, Chaomidian Village, Huangbanjigou [the name of the villige was misspelled in the original descirption]. Yixian Formation, Jurassic-Cretaceous boundary, Late Tithonian-Berriasian, ca. 145–140 mya ( REN et al. 2010). An alternative dating was proposed by SWISHER et al. (1999): Lower Cretaceous, Aptian, 124.6 mya (see REN et al. (2010) for discussion on various datings of Yixian formation).

Material examined ( 1 spec.). HOLOTYPE: CNU 2010004 (piece only).

Description. Body elongate oval, 5.6 mm long. Head with distinct frontoclypeal suture, its median portion grooved; anterior margin of clypeus straight, closely attached to labrum; gula wide, mentum probably transverse. Pronotum with five longitudinal furrows, pronotal intervals bearing dense and fine granulation. Mesoventrite strongly narrowing anteriad, bearing a transverse ridge posteromedially; mesocoxal cavities very narrowly separated; metaventrite ca. twice as long as mesoventrite; metepimeron narrow. Elytron with fine longitudinal series. Abdomen with five ventrites. Legs rather long.

Taxonomic note. The only known specimen was originally considered as a part of the type series of Hydrophilopsia shatrovskiyi (= Laetopsia shatrovskiyi in our concept) by PROKIN et al. (2010). Re-examination of the specimen revealed that it distinctly differs from the holotype of Laetopsia shatrovskiyi in the following characters: (1) pronotum with five longitudinal furrows (only a median furrow present in L. shatrovskiyi ), (2) pronotal surface with granulation (without granulation in L. shatrovskiyi ), and (3) elytral series not darkened (darkened in L. shatrovskiyi ). Moreover, the above characters indicate that the specimen does not belong to Laetopsia but to Helophorus , and due to the lack of synapomorphies of other Helophorus subgenera it should be assigned to the subgenus Mesosperchus . For that reason, the specimen is described here as a new species, Helophorus yixianus .

The species co-occurs with Helophorus (Mesosperchus) gracilis . Both species seem to differ by body measurements ( H. yixianus is much larger than H. gracilis ), more detailed comparison is impossible at the moment due to the bad preservation of the fossils on which the description of H. gracilis was based. Hence, we prefer to assign the above specimen bearing all important diagnostic characters to a separate species, rather than to assign it to H. gracilis which generic placement is only tentative due to the bad preservation of all available specimens and which moreover differs from H. yixianus by its body size.

Figures

Figs. 27–28. Representatives of Helophorus, subgenus Mesosperchus Ponomarenko, 1977. 27 – H. (M.) inceptivus sp. nov. (PIN 4270/1008, holotype); 28 – H. (M.) yixianus sp.nov. (CNU 2010004, holotype). Scale bars: 1 mm. Abbreviations: ant – antenna.