Since both fossils exhibit remarkably similar forewing venation, it is most appropriate to place them within the same genus. They differ in the lengths of the cell between ScP and RA, that of the distal cell between R and MA, and of the cell between branches of M. Collectively, their venation is quite particular, with large polygonal cells and main veins forming pronounced angles. This kind of venation is encountered in some other Acercaria, such as Sphaeropsocidae (Psocodea) or some Hemiptera (e.g., Coleorrhyncha, Heteroptera: Schizopteridae). Regardless, the two new fossils differ greatly from Hemiptera in the simple CuA, a synapomorphy of the Holothysanoptera, versus with an areola postica present in Hemiptera and the Tetrastigmoptera (= ‘Permopsocida’, Permopsocoptera) (Huang et al. 2016). The Sphaeropsocidae have an entirely different pattern of venation (see Smithers 1990: fig. 121; Grimaldi and Engel 2006), except for the early Cretaceous Asphaeropsocites neli Azar, Engel, & Grimaldi, 2010. The latter genus shares with the new fossils veins ScP and RA reemerging as short veinlets from ScP+R, a simple CuA, and three large polygonal cells medially in the forewing, but not homologous, with two between R and M; and the third one between M and CuA (Azar et al. 2010: Fig. 2) rather than between MA and MP in the two new fossils.

The forewing venations of the two new fossils are most similar to those of the Iotacyphidae (originally proposed as a subfamily but herein accorded familial rank), a small clade currently placed in the holothysanopteran lineage as related to Lophioneuridae, and which comprises the genera Iotacypha, Burmacypha, and Retiptera, all from mid-Cretaceous Kachin amber. Zherikhin (2000), Cumming et al. (2024), Shcherbakov et al. (2024), and Shcherbakov and Shmakov (2024) did not justify the attribution of the Iotacyphidae to Holothysanoptera and its subclade Lophioneuroptera. Nel et al. (2012) discussed the position of Burmacypha and suggested that it could belong to the Holothysanoptera based on the simple forewing CuA but also that it is difficult to determine the exact nature of the venation and body structures in the available material of that genus. Iotacypha and Retiptera have elongate mouthparts without any visible mandibles, unlike Psocodea and Tetrastigmoptera, suggesting that these are internalized. Additionally, the distal part of the labrum of Retiptera brennae Cumming, Engel, Lian, & Ulitzka, 2024 has a labral pad partly enclosed in the pair of elongate paraglossae of the labium (Cumming et al. 2024: fig. 4D). This complex structure probably guided the stylets of the laciniae and mandible(s), in the same manner as in extant thrips (Chistolm and Lewis 1984: Fig. 1D,F; Hunter and Ullman 1989: fig. 1B). The presence of a labral pad is also attested in the lophioneuropteran Moundthripidae Moundthrips beatificus P. Nel, Azar, & A. Nel, 2007 (P. Nel et al. 2025), and represents probably a synapomorphy of the Holothysanoptera. Unfortunately, the new fossils do not show clearly the head structures, but both seem to have a buccal cone (Fig. 2), a labral pad, and no strong mandibles that would be visible laterally, and collectively these character states suggest a position in Holothysanoptera.

Cumming et al. (2024: fig. 3) interpreted the forewing venation of Iotacyphidae as follows: CuA and M are basally fused with R and distally reemerge from it, and there is a specialized cua-cup between CuP and R+M+CuA, or M+CuA, or CuA (both synapomorphies of the Acercaria, sensu A. Nel et al. 2012). Based on a comparison of the current fossils, Iotacyphidae, Lophioneuridae, and other holothysanopterans we offer a different interpretation of some details as pertain the interpretations of Cumming et al. (2024), Shcherbakov et al. (2024), and Shcherbakov and Shmakov (2024) regarding CuA, CuP, and 1A.

If we follow the wing venation pattern of the Neoptera as proposed by Schubnel et al. (2020), a supplementary longitudinal main vein is present between the cubital and the anal veins, viz. the postcubital vein PCu. In the Acercaria, this vein is especially important as it is partly or totally fused with CuP. In the photograph of forewing base of Iotacypha zherikhini Shcherbakov, Bashkuev, & Shmakov, 2024 (figured in Cumming et al. 2024: figs 1D, 2A, 3D) and in photographs of the same species in Shcherbakov et al (2024: figs 1–3), a straight, white (desclerotized?), and oblique structure is clearly visible in the area between ‘CuP’ and ‘1A’. This structure merges at the extreme wing base with the vein termed ‘1A’ by these authors. This ‘1A’ emerges from a curved basivenale bulla that has the typical shape of that of the vein PCu. The vein interpreted as the basal part of ‘CuP’ vanishes in the extreme basal part of the area between R+M+CuA and the ‘straight, white (desclerotized?), and oblique structure’. Given that it does not extend more proximally than the bulla, we therefore do not believe that this is CuP. Accordingly, we reinterpret the venation of I. zherikhini as follows: there is a basal fusion of R with M and with CuA in a common stem; CuP is independent of the stem R+M+CuA and corresponds to the ‘straight, white (desclerotized?), and oblique structure’; the vein interpreted as ‘1A’ is PCu and is basally touching CuP, as in many Neoptera, and especially Acercaria; the anal vein is reduced to the basal part of the posterior margin of the wing, note that in Neoptera the extreme base of the anal vein is well separated from the base of Cu and of PCu; cua-cup is the vein interpreted as the basal part of ‘CuP’ by Cumming et al. (2024); CuA emerges first and separately from R+M. CuA emerging first and orthogonal to R+M is interpreted as a putative synapomorphy of the clade Lophioneuroptera (‘Lophioneurida’ sensu P. Nel et al. 2014: fig. 11), this CuA is simple; the vein interpreted as ‘CuA’ by Cumming et al (2024: fig. 2B) is likely M, it is not perpendicular to the radial vein but instead oblique. Its interpretation as ‘CuA’ is not congruent with an attribution of these insects as lophioneuropterans; the vein interpreted as ‘M’ in Cumming et al. (2024: fig. 2B) is RP and the vein interpreted as ‘MP’ is MA, while the vein interpreted as ‘MP+CuA’ is likely MP. It is quite unusual that a vein ‘MP’ would have a reversed course, directed towards the wing base; but if interpreted as MA, then its direction is more ‘usual’.

The fact that the character ‘CuA emerges first and separately from R+M’ is a putative synapomorphy of the clade Lophioneuroptera is not obvious and could be contradicted by its presence in the Tetrastigmoptera, sister group of the Holothysanoptera + Hemiptera (Huang et al. 2016). This would suggest that it is a plesiomorphy or much more likely independently derived and simply a convergence. The relative positions of the re-emergences of CuA and M are highly variable within the Hemiptera: basal to, at the same point as, or distal to M+CuA. The character at least tacitly supports Lophioneuroptera despite its more homoplastic occurrence in a more global phylogenetic distribution.

Based on our reinterpretation (see Fig. 4), in R. brennae the vein ‘CuP’ sensu Cumming et al. (2024: fig. 2C) should be CuA merging distally with CuP+PCu; there is a short common stem M+CuA separating from R, and from which CuA emerges perpendicularly; ‘CuA’ would be M, while ‘M’ should be a crossvein between MA and RP; ‘Rs+M’ should be RP, ‘MP+CuA’ is MP, and ‘MP’ would be MA. Likewise, in Burmacypha longicornis Zherikhin, 2000, there would be a longer common stem of M+CuA than in Retiptera, ‘Cu’ should be M+CuA, separating into CuA (‘CuP’), perpendicular to M (‘CuA’), this CuA merges distally with CuP+PCu+1A (posterior margin of wing), M separates into MA (‘MP’) and MP (‘MP+CuA’), ‘M’ is a crossvein between MA and RP; ‘Rs+M’ would be RP. Forewing ScP is fused basally with R+M+CuA in Retiptera, Iotacypha, and Triassocypha and re-emerges distally as a curved vein in the two former and as a straight veinlet in the latter. In Burmacypha, the vein interpreted as ‘RA’ is in exactly at the same position as in Triassocypha, supporting the hypothesis that it is also the re-emergence of ScP and that ScP basally is fused with R+M+CuA at wing base (and not separated from it).

Figure 4. 

Kachin amber Iotacyphidae, reinterpretation of forewing venation. A Iotacypha zherikhini Shcherbakov, Bashkuev, & Shmakov, 2024. B Burmacypha longicornis Zherikhin, 2000; C Retiptera brennae Cumming, Engel, Lian, & Ulitzka, 2024 (redrawn after Cumming et al. 2024). Abbreviations as in Fig. 3.

Our current reinterpretation of the venation of these insects is congruent with the presence of a CuA that is simple (synapomorphy of Holothysanoptera), and perpendicular to R+M or to M (putative synapomorphy of the Lophioneuroptera, but see below), and with the presence of a PCu (a character of the wing venation groundplan of Neoptera). The reduction of CuA to a short vein in Iotacypha and Burmacypha is also congruent with the general tendency to the reduction of this vein in the Holothysanoptera, CuA perhaps being totally absent in extant Thysanoptera (but see discussion, below, on the absence of CuA in crown-Thysanoptera). Regardless, our interpretation of the venation supports an attribution of these clades to the Holothysanoptera and to the Lophioneuroptera. The new fossils differ from Iotacypha, Burmacypha, and Retiptera in the presence of two closed cells between R and M and a closed cell between the branches of M, versus only one cell between R and M and no closed cell between the branches of M (Fig. 4).

Nel et al. (2012) interpreted the venation of the extant thrips as having no CuA re-emerging from R+M+CuA due to the exceedingly narrow wing and reduced venation. Nevertheless, another interpretation is possible. In the forewing of extant Aeolothripidae, the thrips family with the most complete venation and a wingspan suitable for studying basal venation structures, CuP is fused basally with PCu in a large basivenale bulla, common in all neopteran lineages (Schubnel et al. 2020), and distally separates from it in a longitudinal vein ‘1’ that makes a strong angle and proceeds to the posterior margin as a short veinlet (Fig. 5). At that point, there is a vein that continues the basal part of CuP and ends into a vein ‘2’ that posteriorly emerges from R+M+CuA (Fig. 5). The vein ‘1’ has the same pattern of ornamentation as vein ‘2’, as frequently happens for the cua-cup of Hemiptera. One interpretation is that ‘1’ is cua-cup, and then, vein ‘2’ is M+CuA in which cua-cup terminates. Under this interpretation, CuA would merge with M, and the first short veinlet between M+CuA and the posterior wing margin could be CuA (vs. M2 as proposed by P. Nel et al. 2012). According to this, M would be simple in crown-Thysanoptera and, following this hypothesis, the synapomorphy of crown-Thysanoptera would be that M is simple vs CuA absent as previously proposed by P. Nel et al. (2012). In the representatives of stem-group Thysanoptera, M is forked and CuA remains present. This interpretation is certainly consistent with all observations.

Figure 5. 

Aeolothrips vittatus Haliday, 1836 (Thysanoptera: Aeolothripidae). A General habitus (scale bar = 1 mm), B forewing details (scale bar = 250 μm).

The hypothesis about a re-emergence of CuA from M+CuA is tentative because it is not possible to distinguish the shape and color between the two distal branches of M+CuA. In Thripidae there is no short vein between M+CuA and the posterior wing margin, thus CuA (or M2) is absent as an independent vein. For now, we tentatively consider the hypothesis identifying a cua-cup vein and a re-emergence of M+CuA from R+M+CuA as stronger given the ornamentation of the veins and the position and nature of cua-cup as a crossvein between CuP and CuA (or M+CuA) more widely in the Acercaria. But we do note that the two interpretations of a re-emergence of CuA vs. M2 are challenging to distinguish amongst, and future work is needed in a broader sampling of fossil Holothysanoptera to properly elucidate the situation for crown-Thysanoptera. Furthermore, new comparative anatomical studies based on basivenal bullae and microtomography data (Schubnel et al. 2023) may allow a more accurate identification of the main veins in Thysanoptera, thereby helping to clarify whether the re-emergence of CuA has occurred.