Alegorius, 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 : 715-716

ALEGORIUS GEN. NOV.

Type species: Alegorius yixianus sp. nov., by present designation.

Time range: Early Cretaceous.

Diagnosis: Body medium-sized; labrum partly exposed in dorsal view ( Figs 2A–B , 8A ); anterior margin of clypeus weakly excised mesally ( Figs 2B , 8A ); prosternum moderately long, weakly carinate/ elevated medially ( Fig. 2B ); scutellar shield small, triangular; anapleural sutures well developed, strongly curved, nearly parallel-sided and widely separate anteriorly ( Figs 2A–B , 8B ); mesocoxae very narrowly separated; abdomen with five ventrites; apical abdominal ventrite with deep and narrow emargination ( Figs 2A , 7C ); elytron with deeply impressed sutural stria; elytra with series of punctures ( Fig. 2A ); tarsi of mesothoracic leg with five tarsomeres; mesotarsomere 1 very short ( Fig. 2B ).

Etymology: Alegorius is an arbitrary combination of letters inspired and loosely derived from the given and patronymic names Alexander Georgievich, referring to three Russian specialists on fossil and aquatic beetles, Alexander Georgievich Ponomarenko, Alexander Georgievich Kirejtshuk and Alexander Georgievich Shatrovskiy, who supported the authors of this paper in their palaeontological and taxonomic studies. Masculine.

Family assignment: The combination of large clypeus, well-developed frontoclypeal sutures reaching lateral margin of head closely before eyes, head not constricted behind eyes, small triangular scutellar shield and femora with anteromesal corner not facing trochanter ( Fig. 9 , fmtta) assign the fossil reliably to the family Hydrophilidae s.s. Additionally, it corresponds well with the modern Hydrophilidae in the general habitus and ventral morphology.

Comparison with other genera: Based on the presence of the apical emargination on the posterior margin of the abdominal ventrite 5, Alegorius resembles the extant representatives of the Hydrobiusini and early branching Hydrophilini , and those of the subfamilies Enochrinae and Acidocerinae . In contrast to the Hydrobiusini and Hydrophilini , the mesoventrite of Alegorius is wide anteriorly and does not bear a common ventral keel; in contrast to the Cymbiodyta group of the Enochrinae , the mesothoracic leg bears five tarsomeres. Hence, it seems that Alegorius may be assigned either to the Enochrus -group of the Enochrinae or to the subfamily Acidocerinae . It corresponds with extant species of both clades in general body shape, presence of the shallow anterior excision of the clypeus, and the presence of sharply impressed sutural stria. A more detailed comparison with extant genera is not possible because relevant characters are not preserved in the examined fossils.

Alegorius gen. nov. differs from other Cretaceous fossil genera of the Hydrophilidae especially by the strongly curved anapleural sutures that are nearly parallel and widely separated anteriorly (in contrast to straight anapleural sutures of Cretoxenus gen. nov. and anteriorly joining anapleural sutures of Hydroyixia gen. nov., compare Figs. 8B, D, F ). Detailed comparison with Jurassic fossils described above is not possible due to their incomplete preservation.

Figures

Figure 2. Alegorius yixianus gen. nov., sp. nov. from the Yixian Formation, China. Holotype, CNU 2009079 (A); paratype, CNU 2009078 (B). Abbreviations: abem, apical emargination of abdominal ventrite 5; aes3, metanepisternum; bst, maxillary basistipes; fmtta, free metatibial anterobasal angle; lb, labrum; men, mentum; mstr1, mesotarsomere 1; msv, mesoventrite; pros, prosternum; sstr, sutural stria; tf, transverse fold of prothorax.

Figure 7. Hydrophilid fossils from Early Cretaceous Yixian Formation, China. Alegorius yixianus sp. nov.: holotype CNU 2009079, whole specimen (A), detail of meso- and metaventrite (B), detail of abdominal apex (C); paratype CNU 2009078, whole specimen (D), detail of mesoventrite (E). Hydroyixia elongata sp. nov.: paratype CNU 2009075, detail of head and pronotum (F), whole specimen (G); holotype CNU 2010005: whole beetle, piece and counterpiece (H, I), detail of head (J), detail of meso- and metaventrite (K), detail of abdominal apex (L). Hydroyixia latissima sp. nov.: holotype CNU 2009074, detail of abdominal apex (M), whole specimen in dry condition (N) and under alcohol (O). Abbreviations: apls, anapleural suture; abem, apical emargination of abdominal ventrite 5.

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.

Figure 9. Known distribution of the Hydrophilidae in the Late Jurassic and Early Cretaceous. 1, Solnhofen, Germany; 2, Talbragar, Australia; 3, Baissa, Russia; 4, Yixian Formation, China; 5, Koonwarra, Australia.