Order Diaphanopterodea Handlirsch, 1906

Remarks.

Commonly among Megasecopteromorpha, and more particularly in Diaphanopterodea, MA shows some degree of connection with RP. It ranges from a connection via a strong cross-vein, shortly after the origin of MA, to a full fusion with R, then continuing along RP, from which MA diverges at some stage. Because Diaphanopterodea also exhibit oblique cross-veins, it can sometimes be difficult to determine whether an oblique structure occurring between RP and MP is the genuine MA or a cross-vein. Unlike previous authors (Carpenter 1963, 1992; Béthoux and Nel 2003), Prokop and Kukalová-Peck (2017) suggested that a full fusion of MA with R / RP occurred in Diaphanoptera Brongniart, 1893, the type-genus of the family from which the names of the order derives. These authors based their interpretation on vein elevation as observed in the specimen MNHN. F. R 51214, holotype of Diaphanoptera munieri Brongniart, 1893 . However, our observation reveals that rock compression this particular specimen experienced (like several other Commentry specimens) makes it impossible to derive a solid inference on the elevation of elements attributable to MA. In contrast, the specimen MNHN. F. R 51196 [considered conspecific to the specimen MNHN. F. R 51214 by Béthoux and Nel (2003)] is better preserved in that respect. Our observation revealed that the structure regarded as the base of MA by Béthoux and Nel (2003) and as a cross-vein by Prokop and Kukalová-Peck (2017) is indeed concave, while MA is convex distal to the point where it diverges from RP. This difference in elevation underlies the argument by Prokop and Kukalová-Peck (2017). However, an elevation shift, applying to both MA and CuA, is a general feature of the broader taxon Rostropalaeoptera (Béthoux 2008). Most decisively, in Eukulojidae, whose wings lack cross-venation, the then undisputable bases of MA and CuA are both concave for a short distance before turning convex, after having approached RP and M, respectively (Béthoux 2008: fig. 3). The assumption that MA is fused very early with R / RP in Diaphanoptera is therefore unsubstantiated.