Mesothymbris perkinsi Evans, 1956

Lambkin, Kevin J., 2019, Revision of Mesothymbris Evans, 1956, from the Late Triassic of Mount Crosby, Queensland (Hemiptera: Cicadomorpha: Hylicelloidea: Hylicellidae), Zootaxa 4629 (3), pp. 389-396 : 392

Mesothymbris perkinsi Evans, 1956

(Figs 1–4)

Mesothymbris perkinsi Evans, 1956: 191 , fig. 5D; Evans, 1961: 15, figs 1B, 1C; Evans, 1964: text-fig. 2G; Carpenter, 1992: 224, fig. 144.3; Martins-Neto et al., 2003: 253; Jell, 2004: 39, 2 unnumbered figs.

Mesothymbris woodwardi Evans, 1956 , 191, fig. 5B; Evans 1961: 15; Martins-Neto et al. 2003: 253; Jell, 2004: 39. Syn. nov.

Triassoscytina incompleta Evans, 1956: 179 , fig. 2B; Carpenter, 1992: 225; Martins-Neto et al., 2003: 253; Jell, 2004: 59, 2 unnumbered figs. Syn. nov.

Triassoscytinopsis stenulata Evans, 1956: 190 , fig. 5C; Evans, 1964: 173, text-fig. 2F Martins-Neto et al., 2003: 253; Jell, 2004: 59. Syn. nov.

Triassoscytinopsis aberrans Evans, 1956: 190 , fig. 5J; Evans, 1964: 180; Carpenter, 1992: 225, fig. 144.1; Martins-Neto et al., 2003: 253; Jell, 2004: 59. Syn. nov.

Material (all Mount Crosby). Holotype tegmen UQC889/890, paratype tegmina UQC 183/184, UQC185/186, UQC1547/1548; holotype tegmen of Mesothymbris woodwardi UQC1669; holotype tegmen of Triassoscytina incompleta UQC1559; holotype tegmen of Triassoscytinopsis stenulata UQC917/918; holotype tegmen and scutellum of Triassoscytinopsis aberrans UQC1532/1533. Seventeen additional tegmina: QMF: 3682a/b (= UQE 4/4A), 3684a/b (= UQE S16/16A), 59850 (= UQE 12), 59853a/b (= UQE S1/1A) (the 4 specimens listed as M. perkinsi by Evans 1961), 59851 (= UQE S18) (listed as M. woodwardi by Evans 1961), 6976a/b, 6981, 59852, 59854, 59855, 59856, 59857, 59858a/b, 59859a/b, 59860a/b; ACC: I.6, I.129.

Description. Tegmen 9.3–13.2 mm long, 3.3–4.0 mm wide, length/width 2.7–3.3; branching pattern of RA 2 variable, but always with 3 or 4 terminations; 1A cell varying from quite long and narrow (c. 5 times longer than wide) (Fig. 1), to shorter and much broader (c. 3.5 times longer than wide) ( Fig. 4 ); with a strong pattern of dark markings (Figs 1, 3, 4), particularly evident in the costal space, around R, M and CuA just beyond basal cell, along the RA branches, the proximal area of the CuA cell, along PCu and 1A, in a short band from PCu to the margin, an apical spot on the clavus, and in a broad transverse band from RA 1 through the base of M and then extended posteroapically through CuA 1 and CuA 2.

Notes. Evans (1956) distinguished the tegmen of M. woodwardi on its supposed narrower apex, narrower costal space, three-branched RA 2, and lack of ir and r-m ( Evans 1956, fig. 5B). On examination, however, its holotype, in both shape and venation, is a typical M. perkinsi , with the bluntly rounded apex, a four-branched RA 2, and with both ir and r-m present. The specimen lacks the costal margin which presumably made the costal space appear narrower. The holotype of T. incompleta , is a poorly preserved specimen which, however, contrary to Evans illustration (1956, fig. 2B), preserves the upright RA 1 and the particular shape of the intra-medial cell typical of M. perkinsi . Both the holotypes of T. stenulata and T. aberrans are again typical M. perkinsi . Evans’ illustrations of them do show the upright RA 1, but not the characteristic shape of the intra-medial cell which is present in both their holotypes ( Evans 1956 figs 5C, 5J). Contrary to his description and figure, RP in T. aberrans is simple, not two-branched.

Mesothymbris perkinsi is one of the signature species of collecting at Mount Crosby. Even though there is some variation in the size of the tegmen, it is easily identified in the field by its almost rectangular shape, with a quite blunt apex and fore and hind margins almost parallel, its upright RA 1, and the shape of its intra-medial cell.

Figures

FIGURE 4. Mesothymbris perkinsi Evans, QMF3682a/b, composite of mostly the part (mirrored), and a small section of the counterpart (the lunule-shaped darker area extending from the primary M fork to the top of the specimen).