Zigrasimecia tonsora, Barden and Grimaldi

Barden, Phillip & Grimaldi, David, 2013, A New Genus of Highly Specialized Ants in Cretaceous Burmese Amber (Hymenoptera: Formicidae), Zootaxa 3681 (4), pp. 405-412 : 407-410

Zigrasimecia tonsora, Barden and Grimaldi , new species

Figs. 1–2

Diagnosis, gyne: As for genus.

Description. All numbers in millimeters (mm). HEAD: Broad and flattened; head depth (length) (vertex to clypeal margin, excluding clypeal denticles) 0.66; head width (excluding eyes) 0.76 (1.38× that of mesosoma); distance between inner margins of eyes 0.65, greatest thickness (dorsoventrally) 0.52. Apparently prognathous, with cervical connection near vertex of head. Occipital (posterodorsal) margin of head irregular in dorsal view, slightly emarginate. Postocciput concave. Eyes small, protruding, slightly drop-shaped in lateral view (posterior end narrowed); length 0.21, greatest width 0.13, located on posterior half of head. Ocelli large, diameter 0.06. Vertex with pair of oval-shaped, melanized patches of rugose cuticle. Dorsofrontal portion of head with very fine, sparse setulae. Gena protruding, with apex narrow and extended well past level of clypeal denticles. Frons with dorsoventral portion having very shallow V-shaped groove that meets medially and extends over antennal bases. Frontal carinae absent. Base of antenna obscured by protruding toruli; antennal bases projected laterad from underneath toruli; distance between inner margins of antennae 0.25 (1/3 width of head). Very shallow antennal scrobes present projecting outward laterally from bases of antennae to ventral margin of eyes. Antenna with 12 antennomeres (10 flagellomeres); scape very short, 0.22 length; pedicel 0.13; flagellomeres I–X: 0.17, 0.14, 0.095, 0.095, 0.10, 0.10, 0.09, 0.08, 0.085, 0.14, respectively. Total length of antenna 1.42. Clypeus shallow, length (depth) 0.10 (excluding denticles); broad, distance between lateral-most denticles 0.44; significantly concave in shape (vs. straight). Oral margin of clypeus entirely lined with row of 30 denticles; denticles peg-shaped, with rounded apices, lengths ca. 4× the width. Ventral to row of clypeal margin denticles are two shorter rows of denticles, with approximately 15 denticles in each row. Mandibles short, barely overlapping medially, approximate length 0.345; dentition very simple, with one large apical tooth and large subapical tooth, masticatory margin otherwise devoid of teeth; outside surface of mandible slightly concave; oral surface of mandible with dense brush of stiff, sharp, spicule-like setae. Labrum coated in numerous setae, longer and more narrow than those found on clypeus. Palps short; maxillary palp with 5 segments, total length 0.23 (labial palp mostly obscured).

MESOSOMA: Depth (greatest dorso-ventral distance) 0.60, length (including neck) 1.40; greatest width of mesosoma 0.55;. With sparse, very fine, erect setae on dorsal surfaces (setae slightly recurved on propodeum). Neck long, nearly ¼ the length of true thorax (i.e., mesosoma not including propodeum). Two incomplete, Vshaped sulci present on dorsomedial portion of pronotum. Promesonotal suture complete, extremely well developed. Mesoscutum and mesoscutellum fully demarcated by sulcus; scutellum nearly ½ length of scutum (length of mesoscutum 0.44, mesoscutellum 0.23); dorsal surface of scutellum with pair of deep, rectangular foveae close to median line. Dorsellum well developed, visible dorsally, with pair of shallow foveae dorsolaterally. Laterally: pronotum well developed, without foveae and very few setae; mesopleuron fully separated from the rest of the mesosoma by complete sulci, dorsally bearing C-shaped series of grooves and foveae. Propodeum deep, (depth 0.40); greatest [oblique] length 0.55; declivity steep (in lateral view ca. 65° from horizontal); propodeal spiracle slit-like, facing posteriad, situated on raised base; posterior margin of propodeum shelf-like, with median emargination. Metapleural gland opening large, crescent-shaped; metapleural bulla well developed, hemicylindrical. Petiole deep (depth 0.40), lateral thickness ca. 0.15 [difficult to observe – petiole appears adpressed to anterior wall of metasoma, but most of metasoma obscured by layer of air). Legs: Trochantellus present on all legs, very well separated from trochanter and femur on meso- and metathoracic legs. Claws with large, subapical tooth on ventral margin.

METASOMA: Mostly obscured, apparently large; sting present [best seen ventrally in view from front].

Type: Holotype, JZC Bu-159, dealate female. Myanmar: Kachin State, near Myitkyina, formed near the Aptian-Cenomanian (Early Cretaceous – Late Cretaceous) boundary ( Shi et al., 2012). In James Zigras Collection, available for study through the American Museum of Natural History. The ant is preserved in relatively clear, deep yellow amber; the metasoma is encased within a bubble that obscures most of it.

Etymology. “barber-mouthed,” based on tonsor, barber, hairdresser (L., masculine); and oris, mouth (L.); in reference to the mouthparts bearing combs and brushes.

Figures

FIGURE 1. Zigrasimecia tonsora photomicrographs. (A) Lateral view of entire specimen. (B) Close-up image of mesosoma. (C) Enlarged view of clypeal and mandibular structures. (D) Right lateral view of Head. (E) Alternate left lateral view of head.

FIGURE 2. Drawings of holotype of Zigrasimecia tonsora, as preserved. (A) Head, mesosoma, and petiole, right lateral view. (B) Head and mesosoma, dorsal view. (C) Head, frontal view.