Reisia gelasii ( Reis, 1909 ), 1958

Béthoux, Olivier & Anderson, John M., 2023, New light shed on Triadophlebiomorpha wing morphology and systematics (Insecta: Odonata), Geodiversitas 45 (17), pp. 479-496 : 484

publication ID	https://doi.org/ 10.5252/geodiversitas2023v45a17
publication LSID	urn:lsid:zoobank.org:pub:EE7AA253-A023-4011-B7E1-5820F8118ED3
DOI	https://doi.org/10.5281/zenodo.8399040
persistent identifier	https://treatment.plazi.org/id/31307222-4B5A-FFA7-FE8E-FA709032E697
treatment provided by	Plazi
scientific name	Reisia gelasii ( Reis, 1909 )
status

Treatment

Reisia gelasii ( Reis, 1909)

( Fig. 1 View FIG )

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 View FIG ).

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 View FIG ; two of these pairs visible on Fig. 1C View FIG ). 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 View FIG ; 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 View FIG ). 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 View FIG ) and Piroutetia liasina ( Fig. 3 View FIG ) that it has two branches at least, probably more (in green on Fig. 1A View FIG ). Then, the nature of structures encircled in white on Fig. 1D View FIG 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 View FIG ). 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 View FIG ), 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).