Moltenojurina parva, Béthoux & Anderson, 2021

Béthoux, Olivier & Anderson, John M., 2021, The Polycytellidae viewed as Gondwanan Glosselytrodea, Palaeoentomology 4 (6), pp. 550-558 : 556-557

Moltenojurina parva sp. nov.

( Fig. 4 ) urn:lsid:zoobank.org:act:BFCFDAB4-295D-4C86-A9AB-7441215855A4

Holotype. Specimen PRE/F/20922 (part, preserving a wing in in ventral aspect), Evolutionary Studies Institute , University of the Witwatersrand, Johannesburg, South Africa.

Etymology. The specific epithet, ‘ parva ’ (‘small’ in Latin) refers to the small size of the species.

Diagnosis. Forewing: marginal band broad (opposite the 3 rd quarter of wing length, accounting for about a third of total wing width); apex not deflected posteriorly; small size (forewing length about 3.9 mm in known material).

Type locality and horizon. Birds River (locality code ‘Bir 111’; see Anderson & Anderson, 1984), South Africa; Molteno Formation; lower Carnian, Upper Triassic ( Anderson et al., 1998).

Description. A right forewing, posterior area incomplete, clavus missing, and, according to the proposed reconstruction, area between anterior wing margin and ScP missing; length 3.3 mm as preserved (ca. 3.9 mm if complete), width about 1.1 mm if complete; area anterior to RA broad (0.3 mm opposite the presumed end of ScP), with 4 rows of cells at best, and retaining 2 rows of cells until shortly before the apex; area between RA and MP+CuA ant with 2 veins, zigzagging and without clear origin; area between MP+CuA ant and CuA post with 2 zigzagging veins; in its posterior section, marginal band broad.

Discussion. Because of its incompleteness and the symmetry characterizing Glosselytrodea forewings, it was not straightforward to orientate the specimen. We rested on the fact that the clavus is commonly delimited by a series of rectilinear, close and parallel veins in Glosselytrodea . Provided that it is not the case in the preserved area which could have been interpreted as the clavus, we interpreted it as the area anterior to RA instead. Additionally, veinlike elements preserved in the corresponding area display a zigzagging course, known to be the case for similar elements preserved in the area anterior to RA in Polycytella and Argentinoglosselytrina . In a similar line of reasoning, the lack of a rectilinear vein interpretable as ScP suggests that the specimen was broken along this vein, a damage not uncommon in fossil wings of Glosselytrodea (see Hong, 2007; Rasnitsyn & Aristov in Aristov et al., 2013). A tentative reconstruction was elaborated accordingly ( Fig. 4 ). It implies that the area anterior to RA is very broad, ensuring the assignment of the specimen to the Polycytellidae as diagnosed above.

The new material differs from any known Polycytellidae by its small size. As a matter of fact, to our knowledge, it is the smallest Glosselytrodea to date. More decisively, the marginal band is broader than in other Glosselytrodea : opposite the 3 rd quarter of wing length, the marginal band (anterior and posterior sections) accounts for about a quarter of wing width in Polycytella spp. , while it accounts for more than a third in the new material. These traits justify the erection of a new genus and, incidentally, of a new species.

General similarity between the new material and Mesojurina sogjutensis Martynova, 1943 is regarded as due to the small size characterizing both species. Notably, Mesojurina sogjutensis has an area anterior to RA comparatively narrow, this precluding its assignment to the Polycytellidae as diagnosed above.

Figures

FIGURE 4. Moltenojurina parva gen. et sp. nov., holotype specimen (PRE/F/20922), right forewing. A, Interpretative drawing. B, Photograph (light-mirrored, flipped horizontally).