The Polycytellidae viewed as Gondwanan Glosselytrodea
Author
Béthoux, Olivier
Centre de Recherche sur la Paléontologie - Paris (CR 2 P), Sorbonne Université, MNHN, CNRS, Paris, France
Author
Anderson, John M.
Evolutionary Studies Institute, Witwatersrand University, Johannesburg, South Africa
text
Palaeoentomology
2021
2021-12-14
4
6
550
558
journal article
2961
10.11646/palaeoentomology.4.6.5
73a0820d-7503-472f-8c32-3836cf5fe857
2624-2834
5778576
95AA3380-CA95-46E8-B233-E9F0E8D60603
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.
FIGURE 4.
Moltenojurina parva
gen. et sp. nov.
, holotype specimen (PRE/F/20922), right forewing.
A
, Interpretative drawing.
B
, Photograph (light-mirrored, flipped horizontally).
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.