Podmosta biloba, Chen, 2025

Chen, Zhi-Teng, 2025, Three new stoneflies (Insecta: Plecoptera) from Eocene Baltic amber, European Journal of Taxonomy 1026, pp. 107-122 : 112-115

† Podmosta biloba sp. nov.

urn:lsid:zoobank.org:act:

Figs 4–7

Diagnosis

Vein ra-rp joining anterior branch of RP after fork point in both forewing and hind wings, without typical ‘X-pattern’ at cord. Posterior margin of abdominal sternum 7 membranous, extended backwards. Median sclerite on female abdominal sternum 8 subtriangular basally, apical half bilobed, each lobe slender, extending along lateral margin of sternum 8’s anteromedial indentation.

Etymology

The specific epithet refers to the bilobed median sclerite on abdominal sternum 8.

Type material

Holotype

LITHUANIA • ♀; Lithuanian amber , Eocene, Bartonian to Priabonian, ca 34–38 Ma; beach collected; CZT-PLE-BA1 , ICJUST.

Description

Female

WINGS. In forewing ( Fig. 4A–B), terminal costal crossvein c-r joining RA near ra-rp; ScP reaching RA before ra-rp; RP forked; ra-rp joining anterior branch of RP, distal to RP fork point; CuA and CuP unforked. In hind wings ( Figs 4A–B, 5A–B), terminal costal crossvein c-r joining RA shortly distal to a-rp; ScP reaching RA before ra-rp; RP forked; ra-rp joining anterior branch of RP, distal to RP fork point; CuA and CuP unforked; AA1 simple; AA2 with at least five branches.

TERMINALIA. Posterior margin of abdominal sternum 7 membranous, extended backwards ( Figs 6A– B, 7A). Sternum 8 deeply indented anteromedially, posterior half folded, notched near posteromedial margin; median sclerite subtriangular basally, apical half bilobed, each lobe slender, extending along lateral margin of sternum 8’s anteromedial indentation. Sternum 9 darkly sclerotized, slightly shorter than sternum 8, posteromedial margin slightly extended. Sternum 10 darkly sclerotized, near half length of sternum 9, posterior margin unmodified. Paraprocts subtriangular, with rounded corners. Cerci weakly sclerotized, 2 × as long as wide; apex rounded.

Remarks

† Podmosta biloba sp. nov. is easily distinguished from the five extant species of Podmosta ( Fig. 7) by its uniquely shaped median sclerite on the female abdominal sternum 8 ( Frison 1936; Ricker 1952; Baumann 1975; Chen 2018a; Grubbs & Baumann 2023). It differs from † P. attenuata in the structure of the ra-rp vein, which joins the anterior branch of RP after the fork point in both the forewing and hindwing, resulting in the absence of the typical X-pattern in the cord area. In contrast, in † P. attenuata , the ra-rp vein joins RP before the fork point in both wings, forming the characteristic X venation pattern found in extant species of Podmosta ( Frison 1936; Caruso & Wichard 2010; Grubbs & Baumann 2023).