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| Zygogrylloblatta longipalpa Peng, Engel, Boderau, Legendre, Liu, Nyunt, Wang & Nel, 2025 Artwork by Dinghua Yang. |
Abstract
Extant ice-crawlers (Notoptera: Grylloblattidae) are wingless, ground-dwelling, relict, polyneopteran insects that live in Holarctic cold environments. Their closest living relatives are the similarly apterous bush-crawlers (Notoptera: Mantophasmatodea) from southern Africa, forming together a disjunct bipolar distribution. Meanwhile, numerous winged fossil insects have been assigned to Grylloblattodea, though the lack of defining synapomorphies has complicated efforts to clarify the evolutionary relationships between these fossils and modern wingless ice-crawlers. Here, we report a well preserved winged ice-crawler, Zygogrylloblatta longipalpa gen. et sp. nov., from the Albian/Cenomanian of northern Myanmar (ca 99 Ma). Zygogrylloblatta has the typical forewing venation of Mesozoic ‘stem-Grylloblattodea’, but also exhibits a unique unambiguous synapomorphy of extant Grylloblattidae in male genitalia (coxae IX with apical styli), making it the only fossil accurately related to crown-group Grylloblattidae. In contrast to ground-dwelling habits of extant ice-crawlers, Zygogrylloblatta has well developed wings, arolia and true foot pads, supporting a specialized arboreal lifestyle during the mid-Cretaceous. We demonstrate that Grylloblattidae diverged from some winged, arboreal ancestors prior to the mid-Cretaceous, bridging the gap between ancient stem-group and extant Grylloblattidae. Our results reveal previously unknown ecological and morphological diversity in early ice-crawlers and highlight the significance of transitional fossils in tracing the origin of this enigmatic insect lineage.
Keywords: Insecta, Grylloblattodea, morphology, phylogeny, synapomorphy, male genitalia
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| Zygogrylloblatta longipalpa sp. nov., male, holotype, NIGP206615. Photographs of (a) dorsal view; (b) dorsal view of head; (c) ventral view of head; (d) pulvilli on metatarsus, arrow indicates a puvillus; (e) protibia and protarsus; (f) mesotarsus; (g) posterior abdomen and cerci. (h) Line drawing of forewing. (i) Line drawing of hindleg. Abbreviations: C, costal vein; ScP, posterior subcosta; RA, anterior branch of radius; RP, posterior radius; MA, anterior branches of media; MP, posterior branches of media; CuA, cubitus anterior; CuA1, first branch of CuA; CuA2, second branch of CuA; CuP, cubitus posterior; PCu, post cubitus; AA, anal anterior. 1st, 2nd, 3rd, 4th, tarsomeres I–iV; ar, arolium; car, circumantennal ridge; c, cerci; ce, compound eye; cv, cervix; ga, galea; la, lacinia; lp, labial palpus; mp, maxillary palpus; p, pulvillus; pe, pedicellus; gl, glossa; sc, scape; sm, submentum. Scale bars, 1 mm. |
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| Palaeoecological reconstruction of Zygogrylloblatta longipalpa sp. nov. in a Mesozoic forest. Artwork by Dinghua Yang. |
Systematic palaeontology
Order Notoptera
Suborder Grylloblattodea
Family Zygogrylloblattidae fam. nov.
Genus Zygogrylloblatta gen. nov.
Etymology. The new generic name is a combination of the Ancient Greek noun ζῠγόν/zugón, meaning, ‘yoke’ (in the sense of joining beasts of burden), and the generic name Grylloblatta Walker. The gender of the name is feminine.
Diagnosis. Maxillary palpus extremely long (a putative autapomorphy); tarsal formula 4−5−5; in forewings, no ‘false costa’; RP with three short, apical branches; M and CuA separated; no ‘arculus’; a broad area between CuA and CuP; basal stem of CuA nearly straight; CuA1 with only two branches; CuA2 forming a strong basal curve; ScP short, only reaching two-third of wing length; only rather few simple crossveins between main veins.
Zygogrylloblatta longipalpa gen. et sp. nov.
Type locality and horizon. Hukawng Valley, Kachin State, northern Myanmar; upper Albian–lower Cenomanian (ca 98.79 ± 0.62 Ma).
Etymology. The specific epithet refers to the extremely elongate maxillary palpus.
Ancheng Peng, Michael S. Engel, Mathieu Boderau, Frédéric Legendre, Yu Liu, Thet Tin Nyunt, Bo Wang and André Nel. 2025. Descending from Trees: A Cretaceous winged Ice-crawler illuminates the Ecological shift and Origin of Grylloblattidae. Proc Biol Sci. 292 (2049): 20250557. DOI: doi.org/10.1098/rspb.2025.0557 [18 June 2025]
