Xixia, Gu, Béthoux & Ren, 2014

Gu, Jun-Jie, Béthoux, Olivier & Ren, Dong, 2014, A new cnemidolestodean stem-orthopteran insect from the Late Carboniferous of China, Acta Palaeontologica Polonica 59 (3), pp. 689-696 : 690-694

Genus Xixia nov.

Etymology: From the Chinese Xixia , referring to an ancient name of the area, where the material was collected.

Type species: Xixia huban sp. nov.; designated herein, see below; monotypic.

Diagnosis. —As for the type species by monotypy (see below).

Remarks. —Assignment of the new genus to the taxon Archaeorthoptera is straightforward, as it exhibits a basic diagnostic character of this taxon, namely the fusion of CuA (diverging from M + CuA) with the anterior branch of CuP ( Béthoux and Nel 2002, Béthoux 2007b). The new genus exhibits typical characters of the order Cnemidolestodea , such as ScP reaching RA, and MP diverging obliquely from M and reaching the stem of CuA + CuPa (Béthoux 2005). The connection of anterior veinlet(s) from (MP +) CuA + CuPa with the posterior branch of MA is also a distinctive cnemidolestodean feature.

For comparison with the new material, data on most representatives of the order Cnemidolestodea are available and referenced in Béthoux and Nel (2005a), Béthoux (2005), Gu et al. (2011), and Aristov (2012). Xixia differs from Cnemidolestes Handlirsch 1906 , Ischnoneura Brongniart, 1893 , and Protodiamphipnoa Brongniart, 1885 by its distinct fusion of the most anterior veinlet from MP + CuA + CuPa with the posterior branch of MA. It also differs from Bouleites Lameere, 1917 , Protodiamphipnoa , Cnemidolestes , Ischnoneura , Amphiboliacridites Langiaux and Parriat, 1974 , and Paranarkemina Pinto, 1990 (and closely related species from the Parana basin assigned to various genera, the validity of many of which might be dubious; Béthoux 2007b), by its comparatively distal origin of RP. Among taxa sharing this derived condition, the type species of Xixia differs from most of them (such as Narkemina Martynov, 1930 ; see Sharov [1961], Storozhenko [1998], Aristov [2012]) by its low number of MP + CuA + CuPa branches. This trait is shared with Narkeminopsis species (see Béthoux and Nel [2005a], Brauckmann and Herd [2006]). However, the branching pattern of MP + CuA + CuPa, viz. not clearly internally pectinate, is unique to Xixia . Notice that this trait is shared with Longzhua Gu, Béthoux, and Ren, 2011 , but this taxon has a much more basal origin of RP.

There is a wide variety of forewing coloration patterns within Cnemidolestodea . For example, forewings of Cnemidolestes woodwardi ( Brongniart, 1893) and Narkeminopsis eddi Whalley, 1979 , among others, are covered by parallel and transverse dark stripes. Protodiamphipnoa gaudryi Brongniart, 1885 has dark forewings with an “eye-spot” col- or pattern near wing mid-length in addition to small spots in basal part. Ischnoneura oustaleti ( Brongniart, 1885) and Amphiboliacridites joanesi Langiaux and Parriat, 1974 have several dark and round spots in forewings. The new genus exhibits a coloration pattern previously unknown, composed of dark patches distributed over the whole forewing, without regular stripes or rows of spots.

The distinctive combination of characters exhibited by the type species of Xixia , and the unique coloration pattern, justify the erection of a new genus.

Xixia huban sp. nov.

Figs. 1 , 2 .

Etymology: From Chinese huban , tiger’s stripes; referring to the forewing coloration of the species.

Holotype: CNU-NX1-381 ( Fig. 1A ), well preserved individual, with almost complete wing pairs and undistinguishable thoracic remains.

Type locality: Near Xiaheyan Village, Zhongwei City, Ningxia Hui Autonomous Region, China.

Type horizon: Namurian, Late Carboniferous; Tupo Formation ( Lu et al. 2002).

Material.— Holotype and 11 additional specimens: CNU-NX1-380 ( Fig. 1B ), -382 ( Fig. 2A ), -383 ( Fig. 2B ), -384 ( Fig. 2C ), -385, -387 ( Fig. 2D ), -388 to -391, and -392 ( Fig. 2E ).

Diagnosis. —Forewing: distal origin of RP (closer to wing mid-length than to wing base); MP + CuA + CuPa with few branches (usually 6, ranging from 5 to 8–9); anterior veinlet(s) from MP + CuA + CuPa fused with posterior branch of MA; dark patchy coloration.

Description.—Forewing: length 17.9–21.8 mm, best width opposite second third of wing length) 5.9–7.0 mm; ScP reaching RA, with anterior oblique veinlets; RA and RP diverging near wing mid-length; ScP + RA simple, with strong anterior veinlets; first fork of RP nearly opposite to the fusion of ScP with RA; RP usually with 7 to 8 branches reaching apex, exceptionally 6 or more than 8, rarely with a single veinlet reaching ScP + RA; RP without consistent branching pattern; basal stem of M + CuA close to R for some distance, then directed towards posterior wing margin; M + CuA usually separating into MA and MP + CuA; first fork of MA distal to the origin of RP but basal to the fusion of ScP with RA; MA usually with 3 branches, rarely 2 (?); most anterior branch of MA close to RP but distinct from it (at least in 2 of the observed forewings), shortly connected to it (at least in 1 of the observed forewings), or fused with it for some distance at least in 2 of the observed forewings); free portion of MP + CuA short; area between MA and anterior branch of MP + CuA + CuPa broad, with long and curved cross-veins, rarely with a distinct portion of MP (diverging from MP + CuA + CuPa; if so, it re-fuses with CuA + CuPa); MP + CuA + CuPa with a main anterior stem from which diverge posterior branches, commonly with 5–7 terminal branches, usually 6, occasionally more than 7, in addition to the most anterior veinlet(s), usually fused with posterior branch of MA, rarely fused at the branching point of MA; CuPb weak, strongly concave and simple; AA1 strongly convex, simple, rarely fused with another AA branch; cross-veins reticulated only in broad areas, otherwise distinct and simple.

Holotype specimen CNU-NX1-381 ( Fig. 1A ): well preserved individual, almost complete wing pairs and undistinguishable thoracic remains, positive imprint (with right hind wing in ventral view); right forewing: length 21.0 mm, broadest width 6.6 mm; RP without consistent branching pattern, with 7 (8?) branches reaching wing apex; most anterior branch of MA fused with RP for 0.6 mm, forked close to its divergence from RP; MA with a total of 3 (2?) terminal branches; no evident portion of free MP; MP + CuA + CuPa with 6 terminal branches; left forewing: basal part missing, preserved length ~ 21 mm; RP posteriorly pectinate, with 7 branches reaching wing apex; MA with 3 branches reaching posterior margin, without fusion with RP (see discussion); CuA + CuPa with 6 terminal branches preserved; hind wings: RP originating near or distal to wing mid-length; right hind wing: preserved wing length 13.8 mm; RP with 6 preserved branches; left hind wing: preserved wing length 15.7 mm; RP probably with 5 or 6 preserved branches.

Specimen CNU-NX1-380 ( Fig. 1B ): well preserved, complete, isolated left forewing, positive and negative imprints; length 20.1 mm, broadest width 6.4 mm; RP without consistent branching pattern, with 10 branches reaching wing apex; MA with 3 terminal branches; no evident portion of free MP; MP + CuA + CuPa with 5 terminal branches, with two anterior veinlets (stronger than cross-veins) fused with the posterior branch of MA.

Specimen CNU-NX1-382 ( Fig. 2A ): well preserved and almost complete; isolated right forewing, positive and negative imprints; length about 22 mm, broadest width 6.5 mm; RP with at least 7 branches (assuming that MA has 2 terminal branches); most anterior branch of MA briefly connected to RP; occurrence of strong “veinlet” between MA and CuA + CuPa, possibly being MP reaching CuA + CuPa; CuA + CuPa with 6 terminal branches, with a strong and straight veinlet fused with MA at the point of branching of MA.

Specimen CNU-NX1-383 ( Fig. 2B ): well preserved isolated left forewing, apex missing, positive and negative imprints; estimated length about 20 mm, broadest width 6.5 mm; RP without consistent branching pattern, with 5 preserved branches, and an anterior veinlet reaching Sc + RA; MA with 3 terminal branches, most anterior branch briefly connected to RP, then forked; no evident portion of free MP; CuA + CuPa with 4–5 terminal branches; AA1 and AA2 connected by a strong veinlet/fused.

Specimen CNU-NX1-384 ( Fig. 2C ): well preserved, complete, isolated left forewing, positive imprint; length 20.3 mm, broadest width 6.6 mm; RP without consistent branching pattern, with 7 (8?) branches reaching wing apex, and a veinlet reaching RA (assuming a 3-branched MA); most anterior branch of MA fused with RP for 1.3 mm; distinct portion of MP visible in the area between MA and (MP +) CuA + CuPa, diverging from MP + CuA + CuA and re-uniting with it further; CuA + CuPa with 6–7 terminal branches.

Specimen CNU-NX1-387 ( Fig. 2D ): well preserved, complete, isolated right forewing, negative imprint; length 17.9 mm, broadest width 5.9 mm; RP without consistent branching pattern, with 8 (9?) branches reaching wing apex (assuming a 3/4-branched MA); most anterior branch of MA fused with RP for 1.1 mm; no evident distinct portion of MP; CuA + CuPa with 9 terminal branches.

Specimen CNU-NX1-392 ( Fig. 2E ): well preserved, complete, isolated left forewing, positive imprint; length 21.3 mm, broadest width 7.0 mm; RP without consistent branch-

ScP+RA

CuPb MP+CuA+CuPa ing pattern, with 7–8 branches reaching wing apex (assuming a 3-branched MA); most anterior branch of MA fused with RP for 1.1 mm; no evident distinct portion of MP; CuA + CuPa with 6 terminal branches reaching posterior margin.

Remarks. —In several cases, distinguishing actual fusion of the anterior branch of MA with RP from a mere connection of MA and RP by a short cross-vein is not evidently possible. This is exemplified by the holotype specimen ( Fig. 1A ). Based on the observation that MA is 3-branched in the specimen with obvious lack of fusion ( Fig. 1B ), and provided that the 3 distal branches that can be assigned to MA have no connection with RP in the left forewing of the holotype, we assume that no fusion occurs in this wing (therefore the asterisk on Fig. 1A indicates a cross-vein). In contrast, in the right forewing, only one distal branch attributable to MA has an origin distinct from RP. However, if a fusion is assumed via the element indicated by the open circle on Fig. 1A ), 1 or 2 additional branches can be attributed to MA, which is more consistent with the condition observed in the left forewing. It must be emphasized that the number of MA branches might vary between 2 and 3, rendering several isolated forewings difficult to interpret. A similar range of variation is documented in Narkemina angustiformis (see Aristov 2012).

Apart from this variation, which is definitely of intra-specific significance, the specimens we assign to the new species exhibit limited differences. Variation in size is negligible, compared with that observed in extant relatives e.g., Ciplak et al. 2008; Picaud and Petit 2008; Adis et al. 2008). Variation in aspect ratio can be explained by plastic deformation, known to have affected the material from the Xiaheyan locality ( Cui et al. 2011; Gu et al. 2011; Guo et al. 2013). Such deformation also amplified size differences. Other variations are minimal with respect to those documented in Longzhua loculata , a related species (see original description). Therefore we found no ground to presume that several species compose the set of selected specimens. The coloration pattern observed in forewings of Xixia huban allows the species to be easily distinguished from any other related species, and from all species occurring in the same locality.

Stratigraphic and geographic range. — Type locality and horizon only.

Figures

Fig. 1. Late Carboniferous cnemidolestodean insect Xixia huban gen. et sp. nov. from Xiaheyan, China. A. Holotype specimen CNU-NX1-381; drawing (A 1), asterisk indicates a cross-vein, open circle—the anterior branch of MA fusing with RP; photograph (A 2), LFW, RFW, and LHW as positive imprints, RHW as negative imprint. B. Specimen CNU-NX1-380; drawing (B 1); photograph (B 2), left forewing, positive imprint, flipped horizontally.

Fig. 2. Late Carboniferous cnemidolestodean insect Xixia huban gen. et sp. nov. from Xiaheyan, China; coloration omitted in all drawings; arrows indicate the anterior veinlet from MP + CuA + CuPa fusing with the posterior branch of MA; all figures at the same scale. A. Specimen CNU-NX1-382, drawing (A 1), asterisk indicates a putative free portion of MP, and photograph (A 2), right forewing, positive imprint. B. Specimen CNU-NX1-383, drawing (B 1) and photograph (B 2), left forewing, positive imprint, flipped horizontally.C. Specimen CNU-NX1-384, drawing (C 1), asterisk indicates a putative portion of MP, and photograph (C 2), left forewing, positive imprint, flipped horizontally. D. Specimen CNU-NX1-387, drawing (D 1) and photograph (D 2), right forewing, negative imprint, light-mirrored, flipped horizontally. E. Specimen CNU-NX1-392, drawing (E 1) and photograph (E 2), left forewing, positive imprint, flipped horizontally.