Mesojassus Tillyard, 1916

Lambkin, Kevin J., 2020, Revision of Mesojassus Tillyard, 1916, from the Late Triassic of Queensland (Hemiptera: Cicadomorpha: Membracoidea: Archijassidae), Zootaxa 4718 (3), pp. 413-422 : 415

Mesojassus Tillyard, 1916

Mesojassus Tillyard, 1916: 34 .

Type species. Mesojassus ipsviciensis Tillyard, 1916 , by original designation.

Triassojassus Tillyard, 1919: 167 ; syn. nov.

Type species. Triassojassus proavitus Tillyard, 1919 , by original designation.

Triassocotis Evans, 1956: 194 ; syn. nov.

Type species. Triassocotis australis Evans, 1956 , by monotypy.

Hylicellites Becker-Migdisova, 1962a: 95 ; syn. nov.

Type species. Hylicella reducta Evans, 1956 , by original designation.

Emended diagnosis. Tegmen c. 3 times longer than wide, costal margin broadly convex proximally, almost straight distally, apex narrowly to broadly rounded; 8 full-sized apical cells; precostal carina broad at base, thence tapering to very narrow distally; marginal membrane narrow; costal space broad, more than 2 times as wide as medial cell; CP quite long, extending almost to the point of separation of R and M; costal space and clavus coarsely punctate basally, grading to finely punctate apically, tegmen otherwise smooth; bSc not detected; R and M diverging well before arculus (apex of basal cell); basal cell long, narrow, more or less parallel-sided, closed apically by a very short arculus; R fork at about mid tegmen length, well before level of M fork; base of dSc quite proximal, well before level of apex of clavus; RA with 2 inclined branches; RP simple; one ir, at ⅔ length of RP; one r-m, either slightly basal or slightly distal to ir; M 3-branched, M 1+2 simple; one im, between M 1+2 and M 3; M 3 more or less deflected at im; intra-medial cell c. 4 times longer than wide; CuA 1 more or less deflected towards M 3+4 at the short m-cua; CuA just distal to basal cell weakly curved, quite distant from claval suture; CuA fork well before apex of clavus, at about same level or slightly distal to primary M fork.

Notes. Shcherbakov (2012) divided the Archijassidae into three subfamilies, the Archijassinae , Karajassinae Shcherbakov, 1992, and Dellashariinae Shcherbakov, 2012. With its broad costal space, eight ‘full-sized’ apical cells, long and ‘nearly longitudinal’ CP, and M and CuA 1 connected by a crossvein rather than fused, Mesojassus clearly conforms with Shcherbakov’s diagnosis of the subfamily Archijassinae . The subfamily comprises three additional genera, all from the Jurassic of Eurasia ( Shcherbakov 2012), Archijassus , Mesoledra , and Ardela . Mesojassus is clearly distinct from these in the separation of R and M well before the arculus (at same level or slightly beyond in the others), the proximal position of dSc, well before the apex of the clavus (at or beyond the apex of the clavus in the others), the two-branched RA (simple in the others), one r-m (two in Mesoledra and Ardela ), and the threebranched M (often four-branched in Archijassus and Ardela ) (see figures in Ansorge 1996). The separation of R and M distinctly basal to the arculus is proposed herein as a possible apomorphy for this otherwise most plesiomorphic genus of the Membracoidea. It is noteworthy that this particular character seems to be of frequent occurrence in extant membracoids (e.g. Evans 1964, text-fig. 2; Shcherbakov 1981, figs 25, 26, 33, 35; Shcherbakov 1992, fig. 13).

Shcherbakov (2012) distinguished Mesojassus from Triassojassus by its narrowly-rounded apex and the replacement of m-cua by an ‘X-junction’. The shape of the apex, however, as noted above, varies along a continuum, and in all specimens of Mesojassus examined herein, including the type specimen of Triassojassus proavitus , M and CuA 1 are connected by a short m-cua.