Skleroptera, a new order of holometabolous insects (Insecta) from the Carboniferous

Abstract

A new order of holometabolan insects is proposed for Stephanastus polinae Kirejtshuk et Nel, 2013 from the Upper Carboniferous of Allier, France (Gzhelian, Commentry) (Nel et al., 2013). It is considered a member of the superorder Coleopterida. It shares with the order Coleoptera sclerotised forewings, which demonstrate a simple and somewhat reduced Sc, a simple and concave RP, a convex RA, the M less convex than R and CuA, M also simple and basally fused with CuA (putative synapomorphy), but distally separating from it; stem of M+Cu well separated from R, the coxae do not project and the trochanters are short. The new order Skleroptera ordo nov. differs from the orders Coleoptera and Strepsiptera in the structure of the thoracic sclerites and venation of the forewings, particularly in the following character combination: the absence of lateral carina on the prothorax, the narrow separation of the bases of its forewings, the very narrow anal region of the forewings that widen apically and the absence of a sub-marginal anal (adsutural) vein going along the entire posterior margin of the tegmina. These unique characters of Stephanastus Kirejtshuk et Nel, 2013 suggest that this individual was somewhat laterally compressed (like some orthopteroids). This represents also an essential difference from body ground plan of the Coleoptera in general. It is hypothesized that the position of the new order within the superorder Coleopterida at the subclade level is as follows: Skleroptera + (Coleoptera [probably including Umenocoleidae sensu stricto] +Strepsiptera).