A new, rare and small “lobeattid” species (Insecta: Archaeorthoptera) found at Xiaheyan (Pennsylvanian; Ningxia, China)

Abstract. A new species of stem Orthoptera, namely Phtanomiamia gui gen. et sp.
nov., is described from the Pennsylvanian Xiaheyan locality in China.
Despite the intensive collecting efforts undertaken at this locality, a
single forewing was recovered. It shares with the “lobeattid” Miamia spp. two
peculiar traits, namely a broad ScP–R/RA area and a very early branching
of CuA + CuPa. On the other hand, it displays a free portion of CuA (between
its divergence from M + CuA and its fusion with CuPa), a trait allowing
exclusion of the new species from Miamia, to which it is most likely very closely
related.



Introduction
The Xiaheyan locality has yielded an unprecedented number of specimens of early-Pennsylvanian winged insects. Many species could be documented on the basis of large to very large samples, in particular among the stem lineages of Orthoptera (crickets, katydids and grasshoppers), which dominate the various taphocoenoses from which insect remains were recovered (Trümper et al., 2020). For example, species such as Longzhua loculata Gu, Béthoux and Ren, 2011, Miamia maimai Béthoux, Gu, Yue and Ren, 2012band Protomiamia yangi Du, Béthoux, Gu and Ren, 2017 were described based on several tens of specimens each. However, the undertaken collecting effort also allowed sampling of rare species of stem Orthoptera, including Heterologus duyiwuer Béthoux, Gu and Ren, 2012a and Sinogerarus pectinatus Gu, Béthoux and Ren, 2017, each known from a single, isolated forewing. Herein we report the discovery of another, rare stem-orthopteran species. Because the chances to collect additional material at Xiaheyan are very low, we endeavoured to provide a description despite the meagre sample.

Material and methods
The studied specimen is housed at the Key Lab of Insect Evolution and Environmental Changes, College of Life Sciences, Capital Normal University, Beijing, China (CNU). It was collected from the locality near Xiaheyan village (Zhongwei City, Ningxia Hui Autonomous Region, China; Yanghugou Formation; latest Bashkirian (latest Duckmantian) to middle Moscovian (Bolsovian), Pennsylvanian; Trümper et al., 2020). The exact layer from which it was collected was not documented.
A draft drawing was produced using a LEICA MZ12.5 dissecting microscope equipped with a drawing tube (Leica, Wetzlar, Germany). The drawing reproduced in Fig. 1a was prepared using Adobe Illustrator CC 17.0.0 (Adobe Systems, San Jose, CA, USA) using both draft and photographs. Photographs were taken using a digital camera Canon EOS 450D (Canon, Tokyo, Japan) coupled to a Canon MP-E 65 mm macro lens (equipped with polarizing filter). The resulting photographs were optimized using Adobe Photoshop CC 2015.5. The photograph reproduced in Fig. 1b is a combination of photographs of the dry specimen and when immersed in ethanol. We use the wing venation homologies elaborated by Béthoux and Nel (2002) for Archaeorthoptera. Corresponding abbreviations are the following: ScP, posterior subcosta; R, radius; RA, anterior radius; RP, posterior radius; M, media; CuA, anterior cubitus; CuP, posterior cubitus; CuPa, anterior branch of CuP; CuPb, posterior branch of CuP; AA, anterior analis; AA1, first anterior analis; AA2, second anterior analis.

Type species
Phtanomiamia gui sp. nov.

Masculine.
Etymology A combination of "phtanos", "come earlier" in ancient Greek, and "Miamia", the name of a related genus; referring to close proximity of the new genus with Miamia spp.

Diagnosis
By monotypy, as for the type species.

Type species
Phtanomiamia gui sp. nov.

Etymology
The species name is dedicated to Junjie Gu, for his contributions to fieldwork at Xiaheyan and to the systematics of Orthoptera.

Diagnosis
Forewing: ScP-R/RA area broad (at its broadest, broader than the area between the anterior wing margin and ScP); first fork of M in a distal position (distal to the second fifth of wing length, basal to wing mid-length); CuA + CuPa branched shortly after the fusion of CuA and CuPa; CuA with a distinct, free portion between its divergence from M + CuA and its fusion with CuPa.

Description
Holotype specimen (CNU-NX1-324): negative imprint of an isolated, left forewing, apex missing; preserved length about 12.2 mm, estimated length about 13.8 mm, maximum width 4.2 mm; ScA present, short; ScP-R/RA area broader than area between anterior wing margin and ScP; area between the anterior wing margin and ScP/ScP + RA with strong crossveins, mostly oblique and simple, reticulated near the wing base; ScP reaching RA slightly basal to the second third of wing length; RA/RP fork slightly basal to the first third of wing length; RA simple; RA and RP close and parallel until wing mid-length, where both veins diverge; RP simple for 4.7 mm, posteriorly pectinate (as preserved), with five branches preserved, the anterior-most one reaching RA; M weak, simple for 3.7 mm before it forks into MA and MP; MA simple (as preserved), MP with two preserved branches (it probably possessed 3); CuA 0.5 mm long before its fusion with CuPa; CuA + CuPa forked immediately after the fusion of CuA and CuPa; CuA + CuPa with a total of five branches (2, 3); CuPb simple and straight; area between CuPb and AA1 narrow; AA1 strong and simple, some cross-vein between AA1 and AA2 have cross-veins between them; AA2 with six branches; cross-veins occasionally reticulated; no colouration pattern visible.

Discussion
The new specimen can be confidently assigned to Archaeorthoptera as it exhibits the character "CuA (diverging from M + CuA) fused with the anterior branch of CuP (CuPa)", which is the defining character state of this taxon (Béthoux, 2007). Conversely, assignment to the Panorthoptera (including crown Orthoptera and stem groups closely related to them) can be excluded, as CuPa is not branched before its fusion with CuA. Non-panorthopteran Archaeorthoptera include "lobeattid" insects, the order Cnemidolestodea Handlirsch, 1937 (which is probably derived from a subset of lobeattid insects) and a number of unplaced species. The new specimen displays an RA-RP area narrow for a long distance, a trait occurring in the former, represented at Xiaheyan by Sinopteron huangheense Ren, 2007, Chenxiella liuae Liu, Ren andProkop, 2009 (Béthoux, 2008), a condition implying that CuA does not possess a free portion between its divergence from M + CuA and its fusion with CuPa. This free portion of CuA is present in the new specimen, which represents a plesiomorphy within Archaeorthoptera. In summary, the new specimen belongs to a species closely related to Miamia, yet it can be confidently excluded from this genus. It follows that it belongs to a new species to be accommodated in its own genus. Phtanomiamia gui is smaller than any known species of Miamia, and among the smallest "lobeattid" species.
Data availability. The new material included in the paper is accessible and deposited in the Capital Normal University, Beijing, China, and all data are included in the description.
Author contributions. LC and OB contributed the descriptive section (including preparation of the illustration). LC, DR and OB contributed the Discussion.