Protozigrasimecia

Identification
Worker. Differs from Zigrasimecia tonsora as follows: (1) apical concavity of mandible, subtending distal tooth on the external surface, less pronounced; (2) basal mandibular margin distinctly but shallowly convex along its length to the basal tooth, rather than being more-or-less linear to its apex; (3) one long seta situated on ventral mandibular margin, about 2/3 length of mandible (versus several; single seta state shared with Zigrasimecia ferox); (4) labral traction setae stouter; (5) clypeus with > 30 traction setae; (6) face just posterad posterior clypeal margin without paired transverse sulci; (7) body (head, mesosoma, metasoma) with more-or-less even layer of long erect setae (versus setae much shorter, stubblier); (8) propodeum without median longitudinal groove. Differs from Z. ferox as follows: (1) numerous long erect setae present in malar space of head (versus absent); (2) scape relatively longer (SI [SL / HW] = 0.44 vs. ~ 0.29 - 0.39); (3) foretibia with single spur-like seta posterad calcar; (4) mesosoma evenly arched, propodeum without distinct dorsal and posterior faces (versus mesosoma with dorsal propodeal face angled relative to mesonotum and posterior propodeal face); and (5) body setation longer, denser. Identification supported by the following conditions which are not necessarily unique among Zigrasimecia species: (1) entire body covered with long and erect setae; (2) body length ranging from 2.6mm to 3.5mm; (3) labrum bilobed, with a distinct median notch; (4) eyes small and elliptical to circular; (5) ocelli absent; (6) scape to flagellomeres I or III covered with long and erect setae; (7) antennomeres sequentially and gradually shorter toward antenna apex; (8) anterior labral margin with a row of cincinate (curved) setae; (9) mandible weakly bidentate, with two small denticles; (10) apex of subapical mandibular denticle aligning with apical denticle; and (11) oral face of mandible with 3 rows of erect spiniform setae.

Distribution
This taxon is known from.

Discussion
Cao et al. (2020) - Conclusion: Our study of Zigrasimecia hoelldobleri and Protozigrasimecia chauli reveals both morphological and functional diversity in stem Formicidae. The holotype of Z. hoelldobleri is shockingly well-preserved for light microscopy, and has yielded insights into mandibular, labral, and clypeal function of the Burmese Zigrasimeciini. Based on the interpreted mouthpart function, we colloquially recognize Zigrasimecia and Protozigrasimecia as the iron maiden ants. Among the Zigrasimeciini, we severely doubt that the monotypic genus Boltonimecia from Canadian amber is correct to include, and recommend revised study. In summary, there are ample opportunities for discovery, characterization, and evolutionary analyses of the Zigrasimeciini, which we have attempted to facilitate through the present work.

Nomenclature

 * † PROTOZIGRASIMECIA [†Zigrasimeciinae]
 * †Protozigrasimecia Cao, Boudinot & Gao, 2020: 166. Type-species: †Protozigrasimecia chauli, by original designation.

Uniquely identified among all Formicidae by the diagnostic features listed for Zigrasimeciini and in the Key to the genera of Zigrasimeciini. The new genus is defined by the following combination of character states (see Note 8): (1) head massive, omega-shaped (Ω); (2) anterior clypeal margin broadly concave and arcuate; (3) traction setae present on the anterior clypeal margin and labrum; (4) clypeal traction setae not restricted to single row on anterior margin, but doubling and tripling on clypeus toward cranial midlength; (5) basal mandibular margin evenly convex, ending apically at base of basal tooth; (6) masticatory margin bidentate, comprising well-developed, acute basal and apical teeth; (7) flagellomeres elongate, length > 2 × width; (8) diagonal antennal scrobes present (extending from toruli to anteromedian eye margins); (9) ocelli present; (10) mesosoma diagonal, with domed promesonotum; (11) promesonotal articulation clearly defined and probably mobile; (12) mesonotum well-developed, comprising only mesoscutum; (13) mesoscutellum and metanotum not expressed; (14) propodeum rectangular and box-shaped; (15) propodeal spiracle situated low and laterally on segment; (16) propodeal spiracle slit-shaped; (17) tibial spur formula 2b,2(1b,1s) (b = barbirulate, i.e., with fringed margin, but spur not pectinate); (18) pretarsal claws with denticle situated in basal half; (19) helcium apparently infraaxial (anterior articulatory sclerites of abdominal segment III situated below segment midheight); (20) prora of abdominal sternum III in form of longitudinal keel; (21) abdominal tergum III constricted posteriorly, almost nodiform, albeit segment large; (22) abdominal segment IV with cinctus (tergum and sternum IV divided into pre- and postsclerites by transverse sulcus); and (23) sting robust (Fig. 5D).

Note 8: Because the uniqueness of these characters in comparison to other Zigrasimeciini has already been addressed in the Zigrasimeciini definition, the Zigrasimecia diagnosis, and the key, we simply provide these characters in sequence from anterior to posterior along the body axis. The taxon definition provided here includes characters which encompass meaningful variation among all described and many undescribed stem Formicidae, as well as with relevant comparisons with crown groups. See, for example, Fisher & Bolton (2016) for a comparable approach.

Etymology
The generic name refers to the set of retained plesiomorphic features which distinguish the new taxon from Zigrasimecia (namely, the mandibular dentition and mesosomal form).