Zigrasimecia chuyangsui, Abstract, 2023

Abstract, Júlio Cezar Mário Chaul, 2023, A revision of the Cretaceous ant genus Zigrasimecia Barden & Grimaldi, 2013 (Hymenoptera: Formicidae: † Zigrasimeciinae), Zootaxa 5325 (3), pp. 301-341 : 316-318

Zigrasimecia chuyangsui Chaul, sp. nov.

(Figs. 9–10)

Diagnosis (worker). Medium-sized species. Head more inflated than usual for the genus, apparently subround in full-face view. Frontal carinae poorly marked to absent. Body pilosity composed of abundant, filiform, relatively long, and flexuous setae. Dorsal mesosomal outline conspicuously convex, chubby; propodeum without strongly marked corners between the dorsal and posterior surfaces. Petiolar node thick in lateral view, its dorsal surface developed, round.

Examined material. Holotype worker (ANTWEB1032660). Hukawng Valley , Kachin Province, Myanmar; Lower Cenomanian (ca.98.79 ± 0.62 Ma) [ CELC].

Description. Holotype worker. Measurements: HW 0.85, HL 0.81, EL 0.19, ON ≈90, MesL 0.71, MesH 0.60, PetAFL ≈0.25, Ptg3L 0.60, Ptg4L 0.38, TL 2.75. Head. Head very large, inflated. In anterodorsal view, lateral margins anterad the eyes gradually diverging and, posterad the eyes, converging and forming round vertexal corners and a mildly convex vertexal margin (head could not be examined in a perfect full-face view due to faceting of the stone). Clypeal lobe relatively poorly developed, its area subequal to torular diameter, surface of the lobe slightly laterally turned instead of facing fully dorsally. Clypeal chaetae count around 46. External surface of mandibles smooth, without any carina or swollen areas. Distinct and sharp apical tooth of the mandible; preapical tooth indistinct, fused to the lamella. Spiny chaetae on the oral surface of the mandible barely seen, as mandibles are tightly closed. Labral stout spiny chaetae increasingly thicker apicad. Palpal formula 6, 4. Anterior clypeal margin bearing 46 stout, truncate chaetae. Posterior clypeal margin (epistomal sulcus) poorly marked, but discernible. Anteriormost torular point almost reaching posterior clypeal margin. Frontal carina virtually absent, at most a very mild oblique swelling of the cuticle going from torulus to compound eye. Compound eyes well-developed, slightly bulging. Simple, filiform setae covering the dorsum of head, and antennae; the flagellum has a combination of these setae and smaller, finer, pubescence-like hairs. Mesosoma. Pronotum fused to mesonotum, but a shallow, inconspicuous groove indicates the promesonotal boundary. Pronotum width 0.61 x head width. Mesonotum not delimited posteriorly, nor laterally. Mesopleuron undivided in upper and lower sections, but entirely delimited anteriorly (from lateral pronotum) and posteriorly (from metapleuron), roughly boomerang-shaped. Region corresponding to upper mesopleuron much thinner than that of lower mesopleuron. Metanotal spiracle covered by round, raised cuticle, positioned at the top of the mesopleuron posterior sulcus, and very approximated to the mesonotal spiracle. Posterior mesosoma in lateral view mostly obscured by bubbles, but propodeum appears to be without defined angles or carinae between its dorsal, lateral and posterior surfaces. Dorsum of mesosoma and legs covered on similar setae to those on the head. Protibia with a simple spur-like seta and the calcar; on the mesotibia, two simple spurs subequal in length; on the metatibia, a simple plus a longer and barbulate one. The calcar is as described for the genus, except for having a slightly more developed velum. Arolia developed on all pretarsi. All pretarsal claws with a conspicuous tooth on inner margin. Protarsomeres I-IV bearing a tiny apicoventral, medial truncate chaeta. Metanotal coxa with posterodorsal swelling.

Metasoma. Most of the petiole obscured by a pair of bubbles on each of its sides. Top of petiolar node round. Petiolar ventral process long and digitiform. Prora in lateral view a keel-shaped protrusion, forming an angle of approximately 110º degrees between anterior and ventral margins of the gastral sternite. Cinctus residual to absent. Setae on gaster as on head and mesosoma, denser around the sting

Comments. The specimen has little or no distortion or stretching, and the cuticle is not damaged or desiccated, except for a small cut on vertex caused by the specimen preparation. Bubbles around the petiole, a piece of debris at the apical left side of the gaster, and a leaf remain positioned dorsad the metasoma obscure some views of the specimen.

Among the species that have standing setae on most of the body, Z. chuyangsui can be unmistakably identified for the overall chubby appearance of the body, especially by the shape of the mesosoma, with the lateral, dorsal, and posterior surfaces softly merging into each other, rather than separated by discrete corners and borders.

The tiny ventral, apicoventral, medial, and truncate chaetae seen in the protarsomeres of the holotype of Z. chuyangsui are shared with Camelosphecia Boudinot et al., 2020 , although they are lobate, somewhat hypertrophied in the latter.

Etymology. The name is in honor of Chu Yang Su, the son of Cunte (or "Terry Su"), a kind Burmese/Chinese trader which sold most of the specimens which are being described in this paper. Cunte is by far the largest seller of burmite with animal inclusions on Ebay (currently the most popular platform where burmite is traded outside Myanmar and China). Cunte conducts both mining and trading activities and narrated interesting, adventurous (sometimes dangerous) stories about daily activities in the amber mining camps of northern Myanmar. When asked whether he would like to have a species named after him, he asked whether it could instead be named after his son. The name was created by adding the singular Latin genitive case suffix -i to all names of a male person combined. The orthography of an eponym is unchangeable and not dependent on the generic name in which the epithet is used.