Aristoviblattogryllus minor ( Ren & Aristov, 2011 ) CUI & BÉTHOUX & YANG & REN, 2023

CUI, YINGYING, BÉTHOUX, OLIVIER, YANG, NAN & REN, DONG, 2023, New data and systematic considerations on the Blattogryllopterida (Insecta: Grylloblattida) from the Jurassic Daohugou locality in China, Palaeoentomology 6 (2), pp. 124-132 : 127-131

Aristoviblattogryllus minor ( Ren & Aristov, 2011) , comb. nov.

( Figs 2 , 3 )

Plesioblattogryllus minor Ren & Aristov, 2011: 36 , fig. 1; Cui, 2012: 171, figs 2–5; Storozhenko & Aristov, 24.

Diagnosis. The new genus is similar to Plesioblattogryllus but differs from latter in a long RP+MA fusion with a long basal free part of MA and a very short basal free section of RP.

Material. Holotype CNU-GRY-NN2008001 and newly collected CNU-GRY-NN2023001.

Type locality and horizon. Holotype and newly collected specimen are both from the Daohugou locality, Inner Mongolia, China; Middle Jurassic.

Description. Mediumsizedinsects, bodylengthabout 30 mm, forewing length about 20–25 mm; head with large compound eyes and three ocelli; mandibles asymmetrical; pronotum rectangular with wide ring of paranotalia (lateral expansions of the pronotum); legs ambulatorial, at least fore tibia with a few long spines; coxa enlarged, fore and mid coxa rounded, hind coxa square-shaped; tarsi 5-segmented, segments 1–4 short with poorly preserved euplantulae, fifth segment elongate with a pair of claws and without arolia; female ovipositor straight, about 4.5 mm long; cerci with 10–11 segments, about 7.5 mm long; eggs olive-shaped with strong longitudinal ridges. The details of wing-venation variability are given below.

Holotype CNU-GRY-NN2008001 ( Fig. 2 ): positive and negative imprints of left wing, likely a forewing, with distal part of AA area missing; 24.6 mm long, 7.4 mm wide; ScP ending on anterior wing margin; in distal portion of ScP–RA area crossveins desclerotized along line parallel to ScP and RA, located roughly in middle of area (likely indicating occurrence of flexion line); RA/RP fork in basal third of wing length; RA simple, nearly parallel to ScP; area between anterior wing margin and ScP slightly narrower than ScP–RA area; RP posteriorly pectinate, with four branches; RA–RP area very narrow, parallel to areas between anterior wing margin and ScP, and ScP–RA area; bases of M and CuA free for short distance; CuA arising early, then fused with M for 3.0 mm; MA diverging from M+CuA near basal fourth of wing length, then fused with RP for 3.1 mm, slightly after origin of RP; MA simple; MP diverging from MP+CuA slightly after origin of MA; MP simple, with middle part desclerotised; CuA forked into CuA1 and CuA2 1.2 mm after its origin from MP+CuA; CuA1/CuA2 fork nearly opposite to RP/MA fork; CuA2 simple; CuP strong, straight; AA with anterior-most vein forked; no evident ppa, possibly located basal to second AA vein; cross-veins scalariform, rarely reticulated.

Specimen CNU-GRY-NN2023001 ( Fig. 3 ): negative imprint of right wing, presumably hind wing, with posterior part of anal area folded; 19.6 mm long, 7.2 mm wide as preserved; ScP ending on anterior wing margin; in distal portion of ScP–RA area crossveins desclerotized; RA/RP fork slightly after basal fourth of wing length; RA simple and parallel to ScP; RP posteriorly pectinate, with five branches; area between anterior wing margin and ScP, and RA–RP area slightly narrower than ScP–RA area; base of M invisible; MA diverges from M+CuA in basal sixth of wing length; MA fused with RP for 2.5 long slightly after origin of RP; MA simple; MP diverges from MP+CuA slightly after origin of MA; MP simple, with middle part desclerotised; CuA forks into CuA1 and CuA2 slightly after its origin from MP+CuA; CuA forked earlier than divergence of MA from RP+MA; CuA2 simple; CuP strong, straight; AA with anteriormost vein forked, and both branches crossed by fold (presumably ppa); crossveins scalariform, rarely reticulated.

Remarks. The new specimen CNU-GRY-NN2023001 is roughly identical to the holotype of A. minor except for a slightly smaller size, a 5-branched RP (4-branched in the holotype) and a possibly slightly expanded plicatum.

In contrast with the comparatively larger size of the holotype, with 25 mm in wing length, the multiple specimens investigated by Cui (2012) indicated an average wing length for A. minor around 20 mm, including female individuals, which is consistent with an assignment of the new specimen to this species. However, the new specimen is also wider than the holotype. As a consequence, both specimens differ in general shape. Plastic deformation, already assumed for some specimens from the same locality ( Cui et al., 2015: figs 7C, 8D), may have affected the specimen and caused the observed shape variation. A moderate elongation affecting the holotype along its longitudinal axis, and a moderate elongation affecting the new specimen along the transverse axis, could explain the observed difference. Thus, here we consider that the size/ shape difference displayed by the new material is under the range of intra-specific variation.

In contrast with the general perception that a smaller size entails a reduced venation, the new material exhibits a 5-branched RP, while this vein has 4 branches in most specimens of A. minor , including the holotype. The range of variation of this character is not well-documented for Blattogryllopterida. However, at the level of the order Grylloblattida , such variation commonly occurs within a single species, as demonstrated by species known from large numbers of specimens, and specimens preserving complete wing pairs ( Storozhenko, 1998; Béthoux & Nel, 2010; Aristov & Mostovski, 2013; Storozhenko & Aristov, 2014; Cui et al., 2015, 2022, and others). Thus, a variation ranging from 4 to 5 branches for RP is very likely in A. minor .

Our observation of the new specimen shows that the two branches of the first anal vein are folded along a straight line (orange dashed line on Fig. 4B ). Two possible scenarios on the interpretation of this line are proposed, namely (i) an accidental fold affecting a forewing; and (ii) the occurrence of a plica prima anterior (ppa) crossing AA veins, suggestive of a hind wing. The second scenario is plausible, since ppa is commonly oblique in hind wings of polyneopteran insects. And although it rarely crosses veins in hind wing (but see Béthoux et al., 2011: fig. 3), such configuration cannot be excluded. Notably, in forewings of Mantodea in which the ppa is secondarily oblique, resulting in a somewhat enlarged plicatum, it crosses veins ( Fig. 4 ; and see Demers-Potvin et al., 2021; Béthoux & Wieland, 2009). Under this scenario, the hind wing plicatum would be distinctly reduced in A. minor (but slightly enlarged compared to the forewing yet; Fig. 2B ). Up to now, this state has never been documented in Grylloblattida ( Storozhenko, 1998) . It is worth mentioning that, within Polyneoptera, a secondarily reduced hind wing plicatum has been acquired in Embioptera and within Isoptera ( Ross, 2000; Engel et al., 2009). A third case of reduction is therefore plausible. If this is correct, possessing a reduced hind wing plicatum may compose a distinctive trait of a yet unnamed taxon within the Blattogryllopterida.

Therefore, all the observed differences between the new material and the holotype of A. minor are considered as intra-specific variation.Further substantial investigation on wing venation, especially the hind wing, is needed.

Figures

FIGURE 2. Aristoviblattogryllus minor (Ren & Aristov, 2011), holotype, specimen CNU-GRY-NN2008001, left wing, likely a forewing. A, Photograph (sides composite, polarised light, side P flipped horizontally) and reconstruction. B, Detail of the basal area (as located on A), RTI extract (‘specular enhancement’ rendering mode) and reconstruction (location of ppa uncertain).

FIGURE 3. Aristoviblattogryllus minor (Ren & Aristov, 2011), specimen CNU-GRY-NN2023001, right wing (presumably hind wing). A, Photograph (negative imprint, dry-ethanol composite, flipped horizontally) and reconstruction. B, RTI extract (‘specular enhancement’ rendering mode; as located on A) and reconstruction.

FIGURE 4. Forewing of Mantis religiosa (Linnaeus, 1758) (specimen IWC OB 79, male, left forewing viewed ventrally), photographs. A, Overview. B, Detail of the ppa area (as located on A; arrows indicate veins crossed by the ppa).