Mesosperchus, SCHULTZI PONOMARENKO, 1985, Ponomarenko, 1977

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 : 712-714

‘ MESOSPERCHUS ’ SCHULTZI PONOMARENKO, 1985

Mesosperchus schultzi Ponomarenko, 1985: 142 .

‘ Mesosperchus ’ schultzi: Fikáček et al. (2012a: 123, excluded from Mesosperchus , assigned to Polyphaga incertae sedis).

Type locality and age: Germany, Bavaria, Solnhofen. Solnhofen Formation, Late Jurassic, Lower Tithonian, 150.8–145.5 Mya ( Labandeira, 2003) .

Material examined: Holotype: 1985/20, piece and counterpiece, poorly preserved specimen in a whitish limestone ( Fig. 1C–E, G–H ).

Redescription: Body widely elongate oval. For body measurements, see Table 1.

Head slightly wider than long. Clypeus large, nearly continually arcuate on anterior margin. Frontoclypeal suture present, well developed, reaching lateral margin of head closely before each eye. Eyes large, separated by c. 2.4× the width of one eye. Gula slightly narrowing anteriad, gular sutures widely separate from each other.

Prothorax. Pronotum transverse, narrowing anteriad; anterolateral corners rounded, projecting anteriad. Prosternal process widely triangular. Procoxae contiguous.

Mesothorax. Scutellar shield small, triangular. Elytron with sharply but finely impressed striae.

Legs. Metatibia rather long and slender.

Family assignment: Ponomarenko (1985) originally described this species in the genus Mesosperchus Ponomarenko, 1977 containing three additional Late Jurassic species, and assigned it to the Hydrophilidae sensu lato (which corresponds to the superfamily Hydrophiloidea in current classification). Recent revision by Fikáček et al. (2012a) revealed Abbreviations: HT, holotype; PT, paratype; TL, total body length; HW, head width; CW, clypeus width; IOD, interocular distance; PL, pronotum length; PW, pronotum width; EL, elytron length; EW, elytron width; MSL, length of mesoventrite; MTL, length of metaventrite. Measurements estimated from incompletely preserved body parts are marked by an asterisk.

that M. schultzi does not belong to Mesosperchus Ponomarenko, 1977 , which is now considered a formal subgenus of Helophorus ( Hydrophiloidea : Helophoridae ), comprising its Late Jurassic species (Fikáček et al., 2012a,b). Instead, ‘ Mesosperchus ’ schultzi was shown to resemble modern Hydrophilidae by the shape of the head, presence of the large clypeus and distinct frontoclypeal suture (Fikáček et al., 2012a). Because of the poor preservation and doubts of the authors about the occurrence of the family Hydrophilidae in the Jurassic, Fikáček et al. (2012a) followed a very conservative approach and rather did not include ‘ Mesosperchus ’ schultzi in the family. The discovery of the well-preserved fossil of Protochares brevipalpis gen. nov., sp. nov. clearly demonstrates the occurrence of the family Hydrophilidae in the Late Jurassic, and allows us to be less conservative and assign ‘ Mesosperchus ’ schultzi to the Hydrophilidae . Despite this, additional better-preserved specimens from Solnhofen are necessary to confirm this assignment. Based on this fossil, we consider the occurrence of the modern Hydrophilidae in Europe during the Late Jurassic as highly probable.

Figures

Figure 1. Late Jurassic fossils of the Hydrophilidae. Protochares brevipalpis gen. nov., sp. nov., AMF109568, Talbragar, Australia (A, B, F); ‘Mesosperchus’ schultzi Ponomarenko, 1985, NHMW 1985/20, Solnhofen, Germany: whole specimen (C, G–H), details of the head of the piece using different lighting (D–E). Abbreviations: aes3, metanepisternum; fcs, frontoclypeal suture; gs, gular suture; mttr1, metatarsomere 1; mxp, maxillary palpus; prospr, prosternal process; scstr, scutellar stria; sstr, sutural stria.