1963] 
Carpenter — Diaphanoptera 
251 
Within the order several evolutionary trends are recognizable, of 
which the following four are the most obvious (see plate 30) : 1. The 
costal area, starting as moderately broad (Diaphanopteridae, El- 
moidae) becomes narrowed distally and eventually very narrow for 
its entire length (Asthenohymenidae) . This change is correlated with 
the reduction of the subcosta, which clearly terminates on Ri in the 
Diaphanopteridae but in other families tends to end vaguely in the 
costal space. The cross veins in the costal space also disappear; in the 
Diaphanopteridae, Elmoidae, and Martynoviidae, these veins form a 
definite pattern in the proximal part of the wing, the more basal ones 
slanting towards the wing base, and the immediate ones following 
slanting towards the apex. Finally, the membrane between Ri and 
the costal margin tends to thicken, forming a weak pterostigmal area ; 
this is not visible in the Diaphanopteridae but is in the martynoviids, 
the prochoropterids, and asthenohymenids. 2. The anastomosis of MA 
and Rs increases greatly. In the Elmoidae the anastomosis between 
these veins has not even started, but in the Diaphanopteridae it has 
clearly begun, and the Martynoviidae show a progressive increase 
which eventually leads to the near loss of the basal part of MA 
(Phaneroneura) and the ultimate loss in the Asthenohymenidae. 3. 
The stems of R, M and CuA have become coalesced in the more 
specialized members of the order. In even the most generalized of 
these families, the base of CuA has anastomosed with the stem of M, 
but this compound stem is free from the stem of R (Diaphanopteridae, 
Elmoidae) ; in the Martynoviidae and Asthenohymenidae, these two 
stems have fused. In the process of this change, a definite pattern of 
separation of R, M, and CuA has taken place, this pattern being 
already discernible in the Diaphanopteridae: R diverges anteriorly 
from CuA, the angle between them being bisected by the stem of M. 
This arrangement finally disappears with the loss of the stem of M. 
It is interesting to note that the basal parts of Sc, R, and M + CuA 
are arched in all but the most reduced families, this curvature begin- 
ning in the Diaphanopteridae and reaching its maximum development 
in the Martynoviidae and Asthenohymenidae. 
In addition to the families mentioned above, several others, previ- 
ously assigned to the suborder Paramegasecoptera of the Order Mega- 
secoptera, 5 may also belong to the Diaphanopterodea. These are 
Parabrodiidae and Raphidiopsidae, from the Upper Carboniferous of 
the United States; and Kulojidae and Biarmohymenidae from Permian 
The suborder Paramegasecoptera Carpenter was established (1954) for 
those Megasecoptera which rested with their wings held back over or along 
the abdomen. 
