Pulcherhybosorus Yan, Bai

Yan, Zhuo, Bai, Ming & Ren, Dong, 2012, A new fossil Hybosoridae (Coleoptera: Scarabaeoidea) from the Yixian Formation of China, Zootaxa 3478, pp. 201-204 : 201-203

Pulcherhybosorus Yan, Bai , & Ren, new genus

( Figs. 1–4 )

Type species: Pulcherhybosorus tridentatus new species, here designated.

Diagnosis. Elongate oval. Mandibles and labrum prominent, clearly visible in dorsal view of head, labrum exposed beyond apex of clypeus, mandibles exposed beyond apex of clypeus (fig. 5), anterior margin of clypeus moderately emarginate. Antennae with a 3-antennomere lamellate club, club compact ( Fig. 8 ). Eyes large. Pronotum slightly wider than elytra, nearly trapezoidal, with widest part of pronotum at base. Elytra convex, striae well defined and without tubercles; hind wings well developed, the MP3 vein present and MP4 vein absent. Abdomen with five visible sternites. Protibia with three teeth on outer margin, mesotibia and metatibia without a transverse carina, two spurs on the end of mesotibia subequal in length, and two symmetrical claws on the end of mesotarsus.

Remarks. The new genus is tentatively assigned to the family Hybosoridae based on the following characters: (1) antennae with a 3-antennomere lamellate club, club compact; (2) eyes developed; (3) labrum and mandibles produced beyond apex of clypeus; (4) pronotum trapezoidal, convex, base wider than elytral base; (5) elytra convex, striae well defined, Wings well developed, the MP3 vein present; (6) legs with anterior coxae conical and mesocoxae contiguous; (7) protibia with three teeth; (8) mesotibia and metatibia slightly dilated at the apex, mesotibia with 2 subequal spurs; (9) mesotibia and metatibia without a transverse carina; (10) claws equal in size, simple; (11) abdomen with five visible sternites. Pulcherhybosorus is not placed in a subfamily because of the lack of some key visible characters and the unusual combination of characters.

Beetle fossils with hind wings not covered by the elytra are extremely rare. Pulcherhybosorus tridentatus is the first Hybosoridae fossil species with the hind wing visible and preserved. The hind wings are well preserved and well developed showing the RP, RA3+4, MP1+2, MP3, RP 3+4, RP 2 and RA4+ RP 1 veins. The presence of the MP3 vein and the absence of the MP4 vein are different character states from extant Hybosoridae . This fossil provides an important evidence for the early evolution of Hybosoridae .

Comparison. According to the Hybosoridae fossil record, there are nine genera described from the Mesozoic Era that warrant comparison: Cretanaides Nikolajev, 1996 ; Cretohybosorus Nikolajev, 1999 ; Jurahybosorus Nikolajev, 2005 ; Leptosorus Nikolajev, 2006 ; Libanochrus Kirejtshuk, Azar, & Montreuil, 2011 ; Mesoceratocanthus Nikolajev, Wang, Liu, & Zhang, 2010 ; Mimaphodius Nikolajev, 2007 ; Protanaides Nikolajev, 2010 ; and Protohybosorus Nikolajev, 2010 . The new genus is readily distinguished from the genera Cretohybosorus and Jurahybosorus by the large body size, the mandibles visible in dorsal view, and the long and narrow shape of mandibles. Pulcherhybosorus is distinguished from the genus Leptosorus by the protibia dilated apically and with three teeth on outer margin and by the two spurs on the end of the mesotibia subequal in length. The abdomen with five visible sternites is a reliable diagnostic character that differentiates the new genus from the genus Protohybosorus and Mesoceratocanthus . The new genus is readily distinguished from the genus Protanaides by absence of a transverse carina on the mesotibia and metatibia, and the protibia with three teeth on the outer margin; from Libanochrus by the antennae with a 3-antennomere lamellate club and exposed mandibles; from Mimaphodius by labrum and mandibles visible in dorsal view. Pulcherhybosorus differs from Cretanaides , known from a single elytron impression, by the body size and the absence of tubercles on the elytra. The new genus is distinguished from the extant genera of Hybosoridae by the large body size, the presence of the MP3 vein, and the absence of the MP4 vein.

Etymology. The Latin ‘ pulcher- ’ means ‘beautiful’ in reference to this beautifully well-preserved fossil.

Figures

FIGURES 1 – 2. Pulcherhybosorus tridentatus photographs of the holotype. 1 — CNU-COL-NN 2011002 P (dorsal view of body), 2 — CNU-COL-NN 2011002 C (ventral view of body).

FIGURES 3 – 4. Pulcherhybosorus tridentatus line drawings of the holotype. 3 — dorsal view of body; 4 — ventral view of body.

FIGURES 5 – 8. Pulcherhybosorus tridentatus magnified photographs of some details, 5 — labrum and mandibles; 6 — two spurs on the end of mesotibia; 7 — hind wing; 8 — antennae.