Ideliopsina aristovi Oyama & Béthoux, 2023

OYAMA, NOZOMU, SHINODA, KENJI, TAKAHASHI, HUMIO, DOI, EIJI & BÉTHOUX, OLIVIER, 2023, A new species of the Triassic genus Ideliopsina (Grylloblattida: Ideliidae) from the Ominé locality (Momonoki Formation, southwest Japan), Palaeoentomology 6 (2), pp. 205-213 : 206-208

Ideliopsina aristovi Oyama & Béthoux sp. nov.

( Figs 1–3 )

Holotype. MMHF-3-00101, a right forewing with base and apical area incomplete (two sides, in dorsal and ventral aspects).

Etymology. The specific epithet honors the late Daniil S. Aristov, for his extensive contribution to our knowledge of the evolution of Grylloblattida , and of insects in general.

Diagnosis. Ideliopsina aristovi sp. nov. is distinguished from the congeners by the following combination of characters: first fork of MA located basal to the first fork of RP; MP and CuP straight.

Locality and horizon. Momonoki Formation (Mine Group); Ominé locality, Mine City area, Yamaguchi ( Japan); Carnian (Upper Triassic; Hase, 1951; Ishibashi et al., 1990; Wakita et al., 2021).

Description. Forewing 10.3 mm long, 4.0 mm wide (at its widest), without coloration pattern; anterior wing margin thin; in the median area of the wing, anterior and posterior wing margins not parallel, forming a low angle (10 degrees) instead; area between anterior wing margin and ScP broad (3.6 mm at its widest; 3.3 mm opposite the RA/RP fork); ScP mainly anteriorly pectinate, with 12 main veinlets, sometimes branched (up to three orders of branching, as preserved), with a total 18 veinlets reaching the wing margin (as preserved); RA/RP fork located distally to the MA/MP fork; RA simple, with one anterior veinlet preserved; RP branched 5.4 mm distal to its origin, with a total of 4 branches (as preserved); MA simple for along distance (12.7 mm), with at least one fork; MP desclerotized in the middle of its course (or, wing disrupted or creased in this area), simple, straight; MP– CuA area broader than other areas; CuA main posterior pectinate, with a strong main stem giving rise to 11 distal branches reaching the posterior wing margin, 1 distal veinlet vanishing in the cross-venation, and 4 proximal, well-developed veinlets vanishing in CuA–CuP area (or reaching CuP); CuP weak, straight; cross-venation forming (i) very small cells in the area between anterior wing margin and ScP ( Fig. 3A ), (ii) strong, straight cross-veins connected by weaker ones in the ScP–RA area ( Fig. 3B ), (iii) S-shaped cross-veins near the base of CuA branches ( Fig. 3C ), and (iv) a fine reticulation near the posterior wing margin ( Fig. 3D ); posterior wing margin with crenulation (alternating bulges and depressions; Fig. 3E ).

Remarks. Following Storozhenko (1998), the new species can be assigned to the family Ideliidae owing to the following combination of character states: area between anterior wing margin and ScP broad; CuA with many branches; CuA not clearly differentiated into CuA1 and CuA2; CuA with posterior, proximal veinlets vanishing in the CuA–CuP area or reaching CuP; cross-venation very fine in the whole wing. Within this family, our specimen shares the diagnostic features of the genus Ideliopsina , namely area between anterior wing margin and ScP very broad (about 2.7 times broader than maximum width of RA–RP area); RA simple (or, with mere distal anterior veinlets); R–M area (basal to the RA/RP fork) very narrow; MA straight; CuA proximal branches well-developed; all CuA branches directed towards the posterior wing margin (as opposed to ‘3–5 distal branches of CuA running alongside the posterior wing margin’). Compared with species belonging to Ideliopsina , the new species can be clearly distinguished from I. kenderlykensis , I. nana , I. ornata , and I. stupenda owing to first fork of MA located basal to the first fork of RP. Moreover, unlike I. kenderlykensis , it has a straight CuP. The new species resembles I. ruginosa in the respective positions of the first forks of RP and MA but differs from it by a larger forewing, with a straighter MP.

Structures reminiscent of trichosors, as occurring in Neuroptera, have been reported by Storozhenko (1996) in I. ornata . In the new material we observed bulges and depressions alternating along the posterior wing margin ( Fig. 3D, E ), we propose to term ‘crenulation’. Whether this structure is similar to that known in I. ornata is not evident.

Figures

FIGURE 1. Ideliopsina aristovi sp. nov., holotype specimen (MMHF-3-00101, dorsal aspect). A, Photograph. B, Reflectance transforming imaging (RTI) extract in normals visualization (see Dryad Digital Repository).

FIGURE 2. Ideliopsina aristovi sp. nov., holotype specimen. A, Photograph (MMHF-3-00101, ventral aspect, under ethanol). B, Line drawing.

FIGURE 3. Ideliopsina aristovi sp. nov., holotype specimen (MMHF-3-00101, dorsal aspect), morphological details (except for E, locations as indicated in Fig. 1A). A–C, Details of cross-venation. A, Detail of the area between the anterior wing margin and ScP. B, Detail of the area between ScP and RP. C, Detail of the area between CuA branches (substantiated by dotted lines; ‘CuA’ label indicating the main stem of this vein). D, E, Detail of the posterior wing margin showing crenulation. E, Detail as indicated in D.