Mirabythus Cai, Shih & Ren, 2012

Lepeco, Anderson, Barbosa, Diego N. & Melo, Gabriel A. R., 2022, A remarkable new family of stinging wasps from the Cretaceous of Myanmar and China (Hymenoptera, Aculeata), Journal of Hymenoptera Research 94, pp. 163-190 : 163

† Mirabythus Cai, Shih & Ren

Figs 8

Mirabythus † Mirabythus Cai, Shih & Ren, 2012 in Cai et al. (2012): 58. Type species: † Mirabythus lechrius Cai, Shih & Ren, 2012.

Comments.

In the original description, Cai et al. (2012) considered that the mandibles of † Mirabythus had a series of small notches on the anterior surface. We interpret that these notches correspond in fact to the apical margin of the clypeus, a condition also found in † Prionaspidion gen. nov. and † Trifionyx gen. nov. (more evident in † P. brevidens sp. nov.). The clypeus of † Mirabythus is large, comprising nearly one-third of the entire head length, as indicated by the position of the epistomal groove (Fig. 8C, D ). The apical margin of the clypeus and the anterior surface of the mandibles are aligned in the type specimens, and this is also observed in specimens from Burmese amber. The antennal sockets of † Mirabythus are directed towards the apical margin of the clypeus, below the lower eye tangent (Fig. 8C, D ). Cai et al. (2012) represent with dashed lines at least fourteen articles in the antennae of † M. liae . For us, it is nearly impossible to count the number of antennomeres in the holotype. In the case of † M. lechrius , we can clearly see nine flagellomeres in the holotype, with the first two being far longer than the remaining flagellomeres (Fig. 8A, B ).

It is difficult to determine whether the anterior flange of the pronotum is well developed, but none of the specimens exhibit a long propleura with a wide membranous area medially, as is found in most Scolebythidae . We interpret that the propleura are covered in dorsal view and, therefore, the pronotal flange is present. In both type specimens the legs are curled below the body, hindering the interpretation of structures in the ventral surface of the mesosoma, but two main characteristics can be observed. First, the structure originally interpreted as a large prosternum seems to represent a void area, where the anterior portion of the mesosoma has detached from the mesepisternum (Fig. 8A, B ). In † M. liae this detachment is more evident than in † M. lechrius . We interpret that the basisternum (the ventrally exposed portion of the prosternum) is not as large as in scolebythids, for both species, similar to what is observed in † Prionaspidion nanus sp. nov. Second, a transverse dark line can be seen crossing the mesepisternum of both type specimens (more conspicuous in † M. liae ), which probably represents the angulation of the mesepisternum found in Burmese amber trifionychids (Fig. 8A, B ). This angulation is not found in Scolebythidae . The propodeum has a transverse angulation marking its posterior declivity in both specimens, a characteristic found in the new family, but not in Scolebythidae . The point of insertion of the trochanters on the procoxae is difficult to interpret in both specimens, but it is clearly not basal as in all Scolebythidae . At least one tibial spur is visible in the hind leg of the holotype of † M. lechrius . In none of the specimens of † Mirabythus it is possible to identify a costal cell on the forewing, and we interpret that, as in the species from Burmese amber, the veins C and Sc+R are fused along most of the anterior margin of the wing (Fig. 8A, B ).

Part of the sting apparatus is evident in both specimens, including most of the third valvula, which is unsegmented and apparently has its apical portion permanently exposed. The terebra in the holotype of † M. lechrius also apparently curves upward, as in other † Trifionychidae fam. nov. In Scolebythidae the terebra is curved downward. The third valvula and terebra of † Mirabythus are distinctly elongated, relatively longer in comparison to females of Scolebythidae and other chrysidoids. The two unidentified specimens illustrated by Cai et al. as † Mirabythus indet are putative members of † Trifionychidae gen. nov. as well, although many characters are not clearly visible. Additional figures of † M. lechrius and † M. liae are available at Suppl. material 1: figs S1-S5.

Figures

Figure 8. † Mirabythus Cai et al. A, B † Mirabythus lechrius Cai et al. 2012 A photograph of habitus, ventral view, line drawing superimposed B habitus, ventral view, line drawing isolated C, D † Mirabythus liae Cai et al. 2012 C photograph of head, dorsal view, line drawing superimposed D head, dorsal view, line drawings isolated. Photograph credits: Taiping Gao and Yaping Cai. Scale bar: 2 mm (A, B); 1 mm (C, D).