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
Family
Polycytellidae
Martynova, 1952
stat. rest.
Type genus.
Polycytella
Tillyard, 1922
(including
Polycytella triassica
Tillyard, 1922
, Triassic, Australia; and
Polycytella rasnitsyni
sp. nov.
, Triassic, South Africa).
Other genera.
Argentinoglosselytrina
Martins- Neto & Gallego, 2001 (including
Argentinoglosselytrina pulchella
Martins-Neto and Gallego, 2001
, Triassic, Argentina), and
Moltenojurina
gen. nov.
(including
Moltenojurina parva
sp. nov.
, Triassic, South Africa).
Emended diagnosis.
Forewing: opposite the end of ScP, area anterior to RA large (accounting for about a quarter of wing width).
Discussion.
Genera herein assigned to the
Polycytellidae
display two states that have been generally regarded as relevant to the systematics of
Glosselytrodea
, namely:
(1)occurrence of a single mid-vein (or, ‘two mid-veins fused into a single mid-vein, as opposed to ‘occurrence of two, closely adjoined but distinct, mid-veins’); and
(2) anterior and posterior ambient veins joining each other at their apices (as opposed to ‘anterior and posterior ambient veins reaching the anterior and posterior margins, respectively’).
Martynova (1952
; and see
Martynova, 1962
,
1991
) regarded these traits as diagnostic of the
Polycytellidae
, to which she also assigned
Mesojurina
Martynova, 1943
(including
Mesojurina sogjutensis
Martynova, 1943
, Jurassic, Kyrgyzstan; and see below). However, Rasnitsyn & Aristov in
Aristov
et al
. (2013)
considered that this combination of traits may have been acquired convergently within two distinct families, namely the oligoneurous
Jurinidae
Zalessky,1929
and the polyneurous
Glosselytridae
Martynov, 1938
. Besides the number of veins, which can be partly related to size, this proposal rests on scenarios of forewing elytrization, achieved either by membrane strengthening or veins strengthening. However, these aspects remain difficult to appreciate based on data currently available on
Glosselytrodea
.
Of further interest, it is common that the area between the anterior wing margin and ScP is enlarged in
Glosselytrodea
. Consequently, the anterior wing margin has a marked inflexion opposite the end of ScP. However, in genera herein assigned to the
Polycytellidae
, the area anterior to RA (
i
.
e
., between ScP and RA and then between the anterior wing margin and RA) is also enlarged (opposite the end of ScP, nearly as large as the area between RA and MP+CuA
ant
), with the consequence that the anterior wing margin regains a more continuous course. This trait can be described as follows:
(3) ‘opposite the end of ScP, area anterior to RA large’ (as opposed to ‘RA close to ScP and, distal to the end of this vein, close to the anterior wing margin’).
It is present in
Polycytella
(
Fig. 1
),
Argentinoglosselytrina
and the new material described below (
Figs 2–4
). This trait is most likely derived, as it is unique among
Glosselytrodea
and, to our knowledge, winged insects as a whole. A seemingly similar condition occurs in Blattodea, in which the area between the anterior wing margin and the stem of R is often very wide (
Rehn, 1951
). However, this R stem emits successive anterior branches, the anterior-most ones belonging to RA.As a consequence, the actual area between ScP and RA corresponds to the area between ScP and the first anterior branch of R, and is narrow. The conditions in
Polycytellidae
and Blattodea are therefore not homologous.
Considering that
Mesojurina
displays the plesiomorphic condition of the character (
viz
., the state ‘RA close to ScP and, distal to the end of this vein, close to the anterior wing margin’), we therefore exclude this genus from the
Polycytellidae
, which, as a consequence, is strictly Gondwanan. Whether the corresponding taxon shall better be considered a subfamily to be nested within
Jurinidae
or
Glosselytridae
remains to be elucidated.