Phyloblatta gaudryi

Phyloblatta gaudryi (Agnus, 1903)

DESCRIPTION. — Negative imprint, right and left forewings, and left hind wing of a single individual, connected to remains of the pterothorax (wing venation described as if viewed from a positive imprint; numerical data: right / left side); forewings: length 35.8/34.0 mm, width 14.3 / 14.8 mm; ScP reaching anterior wing margin at between 60 and 75% of the wing length; ScP concave, with numerous anterior branches; R concave, branched about 7.5 / 6.8 mm distal to wing base, with no regular branching pattern; R with 13 / 14 branches; M (excluding its branches associated with CuA) branched distal to R, concave, anteriorly pectinate in right forewing, irregularly branched in left forewing; M with 11 / 9 branches free of CuA; convex transverse to oblique, and somewhat irregular veinlets interconnecting M and CuA proximal to the branching of both, with a stronger basal veinlet and one / several weaker veinlets; CuA convex; branches of M diverging from CuA + M partim concave; M partim + CuA with 17 / 18 branches; CuP simple, strongly curved, strongly concave, reaching the posterior wing margin near 40% of wing length; anal area with 16 / 14 AA branches, all reaching the posterior wing margin; hind wing: length 29.4 mm, width of remigium 13.3 mm; vannus folded over remigium (whether the vannus is provided with longitudinal folds, or not, cannot be observed); ScP concave, reaching the anterior wing margin at mid-length; R convex, branched 5.7 mm distal to wing base; RA convex, branched distally, with four branches; RP concave, branched 3.9 mm distal to its origin, anteriorly pectinate, with 11 branches; M concave, weak at its origin, with three branches free of CuA; a simple branch of M diverges anteriorly from M partim + CuA; CuA located in a depression but concave, posteriorly pectinate, with six branches; CuP concave, sigmoid, weak, simple; AA(1?) (located on the remigium) with three branches reaching the posterior wing margin; basal to its main fork, AA(1?) emits two strong struts posteriorly; fold separating the remigium from the vannus crossing two veins (Fig. 3 [°]), and reaching the posterior wing margin at 38% of wing length; vannus moderately large, filled with numerous branches (belonging either to AA1 or AA2, see below).

REMARKS

The specimen most likely experienced moderate plastic deformation during fossilisation, as indicated by the forewings aspect ratio, differing in the right and left forewings. The difference observed in the fossil individual exceeds that observed between right and left forewings of Periplaneta americana (Linnaeus, 1758) (Schneider 1977: fig. 2).

Béthoux O. et al.

VARIABILITY

As detailed by Schneider (1977: 81, pl. 2), the forewing venation of Phyloblatta gaudryi is particularly variable with respect to other Palaeozoic stem-Dictyoptera. In particular the number of terminal branches and branching pattern of each vein (sector) varies considerably (e.g., the number of terminal branches of the anterior branch of R ranges from 1 to 9 (Schneider 1977: pl. 2, figs 12, 11, respectively).