Fig. 20 (opposite page). Thamnopteros uniserius Galea gen. et sp. nov., portion of fascicled stem giving rise laterally to a Halopteris-like branch, of which only the proximalmost part, showing the prosegment, is depicted (A); more distal portion of another branch, note slight change in the hydrothecal shape (the arrow indicates a cladial apophysis) (B); two cauline hydrothecae seen laterally, to show variation in the length of the lateral nematothecae (C–D); cladial hydrothecae seen laterally (E) and frontally (F), note differences in the size of the lateral nematothecae belonging to each pair; detail of the hydrothecal axil (G); nematothecae: mesial (H), of the component tubes of the fascicled stem (I), and from above the cauline hydrothecae (J); gonotheca (K); all from sample MNHN-IK-2015-611. Scale bars: A–B = 500 µm; C–F = 200 µm; G–J = 100 µm; K = 300 µm.