FIGURE 4. (a) Cladogram showing likely phylogenetic relationships of the fossil families reviewed here, mapped to the consensus phylogeny based on Letsch et al. (2021), South et al. (2021) and Garcia-Giron et al. (2024). Dotted lines represent the uncertain affinities of Southern Hemisphere Permian "Eustheniidae" to Antarctoperlaria, and †Cavoperlidae to Pternonarcyioidea, respectively. Fossil species that are recommended as calibration points for future phylogenetic studies are represented by letters in blue circles. (b) Time scale showing relative ages of key calibration points for the phylogeny of Systellognatha. Calibration points: A: First stem-Plecoptera: †Gulou carpenteri Béthoux et al. (314.6–311.45 Ma) & †Gulou oudardi Schubnel et al. (314.6–306.95 Ma).?: Lack of clear fossil representatives of the earliest Antarctoperlaria and Arctoperlaria. B: First Gripopterygidae: †Eodinotoperla duncanae Jell & Duncan (122.46–112.6 Ma). C: First stem Notonemouridae: †Talbragaria australis Sroka & Prokop (157.3–145.0 Ma). D: First Peltoperlidae: †Ecdyoperla fairlightensis Sinitshenkova (145.5–140.2 Ma). E: First Pteronarcyidae: †Pteroliriope sinitshenkovae Cui et al. (164.7–155.7 Ma). F–I: First stem-Perloidea: F: †Platyperla platypoda Brauer et al. (183.0–155.7 Ma), G: †Platyperla conferta Sinitshenkova (171.6–164.7 Ma), H: †Bestioperlisca inulta Sinitshenkova (150.8–145.5 Ma), I: †Trianguliperla quassa Sinitshenkova (140.2–125.45 Ma). J: First Perlidae: Several species from Myanmar, e.g. †Lagusoperla acus Chen et al. & †Electroneuria ronwoodi Sroka et al. (99.7–94.3 Ma) K: First Perlodidae (& Isoperla): Isoperla †baltica Jouault et al. (37.2–33.9 Ma).