1974] 
Kukalova-Peck — Pteralia 
425 
Fig. 9. Incomplete wing base of Asthenohymen dunbari (Diaphanop- 
terodea, Asthenohymenidae) . Fore wing. Original. B — basal fold; S — 
sclerotized region. Lower Permian, Kansas. 
with the proximal margin of the axillary plate and with R. It is in 
the position of 2 Ax in Recent Ephemeroptera ( sensu Tsui and Peters 
1972, fig. 5). 
In Asthenohymenidae, the incompletely preserved wing base, in- 
cluding only the basal fold and part of the sclerotized region, is 
known. The structure of the wing base, as preserved in Asthenohy- 
men dunbari (specimen No. 3835, Museum of Comparative Zoology, 
fig. 9) seems to be basically similar to that of Martynovia and 
P ermodiapha. 
The fused axillary plate of Diaphanopterodea is homologous only 
to the posterior part of the subcosto-anal plate of Palaeodictyoptera. 
The subcostal, radial, and possibly also the median basal plates be- 
came completely reduced, perhaps in connection with narrowing of 
the wing base, coalescence of veins and with acquisition of wing 
folding ability. 
Megasecoptera 
The Megasecoptera and Palaeodictyoptera have very similar mouth- 
parts, genitalia and wing venation pattern, and undoubtedly developed 
from common ancestral stock. The Megasecoptera differed, accord- 
ing to our previous understanding, only in the shape of the wings 
and in the more pronounced crowding of Sc and R towards the 
costal margin. However, the study of the wing base has revealed a 
