Burmeumastax, Husemann & Schall & Uchida & Kotthoff, 2025

Husemann, Martin, Schall, Ole-Kristian Odin, Uchida, Kei & Kotthoff, Ulrich, 2025, The first Cretaceous Eumastacoidea (Orthoptera, Caelifera) from Burmese amber, Journal of Orthoptera Research 34 (1), pp. 151-157 : 151-157

Genus Burmeumastax gen. nov.

Figs 3 , 4

Type species. —

Burmeumastax lexiae sp. nov., by monotypy.

Etymology. —

The genus name derives from a combination of the words “ Burma ” and “ Eumastacidae ” in reference to its geographical and phylogenetic affiliations, respectively.

Diagnosis. —

Pronotum with two distinct grooves. Anterior groove smooth, posterior groove sharp. Brachypterous. Last abdominal tergite consisting of 5–7 plates. Supraanal plate elongate, triangular. Sub-genital plate bulbous with apical central fold and lateral cercus-like lobes. Cercus slender, same length as supra-anal plate. Cercus and sub-genital plate setulose. Only dorsal (= middle) plate of last abdominal tergite setulose.

Remarks. —

Systematic placement of Burmeumastax inside Eumastacoidea is difficult. As Burmeumastax is a brachypterous genus, a comparison with most other fossil genera of the superfamily is impossible. The only two fossil genera that can be compared with Burmeumastax are Eoerianthus Gorochov, 2012 and Paleomastacris Perez-Gelabert et al., 1997 . The type and only species of the first genus, E. eocaenicus Gorochov, 2012 , is from the Eocene (56–33.9 Mya) of North America (Wyoming, Green River Formation) ( Gorochov and Labandeira 2012), thus separated from Burmeumastax by at least 40 My. Morphologically, Eoerianthus differs from Burmeumastax in having a body three times longer, featuring fully developed wings, a very different pronotum morphology with no dorsal grooves, and no small spines on the metafemur ( Gorochov and Labandeira 2012). The abdominal apex and external genitalia were not preserved in the specimen of Eoerianthus . Paleomastacris ambarinus Perez-Gelabert et al., 1997 , type and only species of the second genus, differs from Burmeumastax by being completely apterous, a pronotum without dorsal grooves, and external genitalia of alternate shape. The supraanal plate of P. ambarinus is diamond-shaped, while it is triangular in B. lexiae . The sub-genital plate consists of two ventrally separated triangle-shaped parts in P. ambarinus but is bulbous with a ventral fold in B. lexiae .

Without knowledge of the internal genitalia and specifically the phallic complex, attribution of Burmeumastax to one of the seven extant families of Eumastacoidea is problematic, as other morphological characters that could be used for diagnosis are lacking in this understudied group. Burmeumastax differs from modern-day Eumastacoidea by its last abdominal tergite consisting of several (5–7) separate parts. In extant species, this structure is made up of one joint or two lateral plates with just a small space dorsally ( Dirsh 1966, Descamps 1979, Rowell and Bentos-Perreira 2001).

Figures

Fig. 3. Burmeumastax lexiae gen. et sp. nov. holotype male GPIH _ 07011. A, B. Image and drawing of specimen’s right side, respectively. C. and D. Image and drawing of specimen’s left side, respectively. E, F. Image and interpretative drawing of the abdominal region including external genitalia. Abbreviations: abd = abdomen; tg = forewing; mt = metatibia; mf = metafemur; pr = pronotum; h = head; ptl = prothoracic leg; pa = palpus; msl = mesothoracic leg; e = eye; lat = last abdominal tergite; ce = cercus; sap = supra-anal plate; sgp = sub-genital plate. Scale bars: 5 mm (A, B, C, D); 1 mm (E, F).

Fig. 4. Burmeumastax lexiae gen. et sp. nov. holotype male GPIH _ 07011. A. Detail of the head. B. Detail of the pronotum. Abbreviations: pg = pronotal groove. Scale bars: 1 mm.