3.2.2. † Tshekardoperlidae and † Palaeoperlidae The placements of † Tshekardoperlidae Sinitshenkova and † Palaeoperlidae Sharov are uncertain. While many of the component species are figured with a short basal tarsomere (Aristov et al. 2013; Sinitshenkova 1987, 2018), this is the only apomorphy present in both families. Wing venation in † Palaeoperlidae retained the plesiomorphic condition.As these families are much older than the other stem-Systellognatha discussed here (limited to the Permian vs. Jurassic and Cretaceous), it is safer to not assign these families to the crown group, although it is possible that they represent a very early stem-ancestor of Systellognatha.

Published as part of Kirkaldy, Abigail P., Barber-James, Helen M., Richoux, Nicole B. & Villet, Martin H., 2025, Literature review of the fossil record of Systellognatha (Insecta: Plecoptera) and its implications for the biogeography of the Order, pp. 301-332 in Zootaxa 5716 (3) on page 314, DOI: 10.11646/zootaxa.5716.3.1, http://zenodo.org/record/17889369