Reisia gelasii Laurentiaux 1958
Creators: name: Béthoux, Olivier
name: Anderson, John M.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Odonata
Triadotypidae
Reisia
Reisia gelasii

description: Reisia gelasii (Reis, 1909)
(Fig. 1)
Handlirschia gelasii Reis, 1909: 694, figs 1-7.
Reisia gelasii – Handlirsch 1912: 6. — Schmidt 1928: 329, fig. 903. — Grauvogel & Laurentiaux 1952: 128, fig. 5. — Laurentiaux 1958: 37 (partim) — Bechly 1997: 53 (partim). — Nel et al. 2001: 507, fig. 4.
EXAMINED MATERIAL. — Holotype and only known specimen SNSB-BSPG 1908 I 49 (right wing in dorsal aspect; ‘ Bayerische Staatssammlung für Paläontologie und Geologie’, Munich, Germany; Fig. 1).
TYPE LOCALITY AND STRATIGRAPHY. — Münnerstadt, Germany; Muschelkalk basin, Schaumkalkbänke Member, Jena Formation; Anisian, Triassic (Paleobiology Database; Nel et al. 2001).
EMENDED DIAGNOSIS. — Width opposite the RP1/RP2 fork about 22 mm (lower in Reisia nana); in the area delimited anteriorly by RP2 and posteriorly by the first I- between RP3+4 and MA, approximately in the median area of the wing (between the origin of the first I- in the RP3+4 and its first fork), cross-venation denser than in surrounding areas (autopomorphic trait); MP with 4 main posterior branches (in addition to its anterior stem; lower in Reisia rubra n. comb.).
REMARKS
Among triadophlebiomorphans, the comparatively high density of cross-veins in the median area of the wing is unique. We submit that it is relevant to distinguish Reisia gelasii from other Reisia species (area poorly known in Reisia rubra n. comb., but which has fewer MP and CuA branches; area unknown in Reisia nana, which is distinctly smaller).
There is little to add to the original description by Reis (1909) of the available material. Yet, the exceptionally wellpreserved vein corrugation provides interesting clues on how intercalaries can mimic main veins. In the distal part of the RP3+4-MA area four pairs of convex and concave intercalaries (I+ and I-) arise from regularly convex cross-veins, close to RP3+4 (Fig. 1B, C; two of these pairs visible on Fig. 1C). More basally, a very similar pair of intercalary arises from a cross-vein which elevation can be considered neutral. Even more basally, the concavity typical of the I- of the pair applies to the cross-vein in connection with RP3+4. In other words, the I- of a pair of intercalaries adopts a vein-like origin. This case clearly supports the view that the apparent posterior (concave) branch of RP3+4 is more likely an extensively developed I-.
Another relevant aspect of wing venation homology for which the specimen provides some clues regards the number of MP vs CuA branches, a point that could be referred to as the ‘MP-CuA twilight zone’. In its distal part, MP is undoubtedly provided with three posterior branches (Fig. 1B, D; the most distal and most basal ones have a clear concave origin; only the most basal one of the three is visible on Fig. 1D). More basally, concave structures do not display such clear concave origin from MP. As for CuA, even though its basal stem is not preserved, it can be assumed from data on Reisia guillaumei n. comb. (Fig. 2) and Piroutetia liasina (Fig. 3) that it has two branches at least, probably more (in green on Fig. 1A). Then, the nature of structures encircled in white on Fig. 1D is not obvious. A first interpretation, favoured herein, predicts that a CuAprlg (see ‘Material and methods’ section) might begin to form, crossing one posterior branch of MP (which putative base is indicated by ‘0’ on Fig. 1D). This vein would then have a total of five main branches (four posterior branches in addition to the ending of its main stem), and CuA three preserved ones, and most likely four in total, as in Reisia guillaumei n. comb. A second interpretation predicts that CuA extends further, with a total of five main branches (four preserved and one inferred), and MP four (including its main stem). The case of Piroutetia liasina (Fig. 3), where no CuAprlg can be assumed, shows that CuA has fewer branches than MP (two vs three). We therefore favour the interpretation that, in Reisia gelasii, a CuAprlg occurs along a short section and that CuA most likely had four branches (three of which are preserved).
description: Published as part of Béthoux, Olivier & Anderson, John M., 2023, New light shed on Triadophlebiomorpha wing morphology and systematics (Insecta: Odonata), pp. 479-496 in Geodiversitas 45 (17) on page 484, DOI: 10.5252/geodiversitas2023v45a17, http://zenodo.org/record/8399030