Zigrasimecia perrichoti, 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 : 321-323

Zigrasimecia perrichoti Chaul, sp. nov.

( Fig. 12 )

Diagnosis (worker). Medium-sized species. Head subrectangular in full-face view. Standing or conspicuous decumbent setae absent on dorsum of head, mesosoma and most of metasoma (except on apex of gaster, A5– A7); minute pubescence likely present. Petiolar node without a well-formed dorsal surface; apex transversally not bilobed.

Examined material. Holotype worker (UFV-LABECOL-010301). Hukawng Valley , Kachin Province, Myanmar; Lower Cenomanian (ca.98.79 ± 0.62 Ma) [ CELC].

Description. Holotype worker. Measurements: HW 0.73, HL 0.81, EL 0.21, ON ≈90, MesL 0.75, MesH 0.50, PetAFL 0.34, Ptg3L 0.60, Ptg4L 0.36, TL 2.86. Head. In full-face view, head subrectangular, lateral margins mildly diverging posteriorly from the most constricted level (just posterad the clypeal lobes) to the compound eyes level; vertexal margin mildly concave and vertexal corners neither too weakly, nor too strongly marked. Clypeal lobe well-developed, its width much larger than torular diameter. Clypeal chaetae count around 34. Portion of dorsal surface of mandible, which is ventrally turned, with a filiform, erect seta on its middle. Teeth on masticatory margin of mandible as for the genus, but apical tooth relatively large. Spiny chaetae on ventral surface of mandible and stout labral chaetae as for the genus, the distribution of chaetae on labral disc is not visible. Labral distal margin not visible. Labio-maxillary complex including all palpomeres not visible. Posterior clypeal margin (epistomal sulcus) weakly marked. Frontal carinae well-impressed. Dorsal surface of the head with abundant piligerous marks, but no setae visible. This punctation is likely the marks of very fine head pubescence (difficult to confirm). Antennae without standing setae. Mesosoma. In profile, dorsal mesosomal outline gently convex, meeting an oblique posterior propodeal margin at a marked angle. In dorsal view, mesosomal outline subrectangular, lateral margins flat to mildly convex, region corresponding to promesonotum slightly wider than that corresponding to propodeum. Propodeum in dorsal view with a flat to mild concave posterior margin. Propodeal spiracle slit-shaped, relatively small (0.05 mm, about 10% mesosoma height). Protibia having a pair of simple spur-like next to the calcar; calcar velum poorly-developed, tip of calcar frayed; mesotibial spurs subequal, the posterior one with inconspicuous barbulation; metatibial smaller (anterior) spur simple, larger (posterior) spur pectinate. Metasoma. In lateral view, anterior petiolar margin convex, apex only a brief curvature which leads to posterior descending margin which is also convex, especially on the lower portion. Petiole in anterior view subrectangular, the apical transverse margin almost straight. Although not forming a conspicuous dorsal surface, petiole is relatively thickened, not sharpened on the apex or lateral edges. Gaster large. A mild cinctus present on A4, indicated by a soft curvature at the edge of A3 tergite which articulates on A4 pretergite. Metasoma glabrous, except for A5–7, which bears several curved, long, simple setae on its edge. Sting tip exposed.

Comments. The specimen has little or no distortion or stretching, the cuticle is not damaged or desiccated. The matrix is very clear, but has a fracture that crosses the specimen from side to side, passing in the head posteriorly and upper mesosoma. The fracture causes a mirroring effect which does interfere significantly with the visualization of the ant, however, multiple facets and different illumination might reveal parts that are obscured by that artifact.

Zigrasimecia perrichoti cannot be mistaken for its congeners as the almost entirely glabrous body differentiates it from Z. ferox , Z. hoelldobleri , Z. boudinoti , and Z. chuyangsui . Zigrasimecia thate and Zigrasimecia ufv-11, which are mostly glabrous, have patches of conspicuous setae on the dorsum of the head. In fact, Z. perrichoti is overall very similar to Zigrasimecia ufv-11, having a very similar head shape, differing mainly on head pilosity and compound eye size. Zigrasimecia caohuijiae shares with Z. perrichoti the lack of standing setae on the body, but it is much smaller, with relatively smaller compound eyes, and a differently shaped mesosoma and head. Regarding the two species described based on queens, Z perrichoti is unlikely the worker caste of Z. goldingot for having more clypeal chaetae and a more rectangular rather than quadrate and unlikely the worker caste of Z. tonsora for lacking standing body pilosity.

Etymology. The name is in honour of the great paleontologist Vincent Perrichot. The name was created by adding the singular Latin genitive case suffix -i to the last name of a male person. The orthography of an eponym is unchangeable and not dependent on the generic name in which the epithet is used.

Figures

FIGURE 12. Holotype of Zigrasimecia perrichoti (UFV-LABECOL-010301). A, full-face view of the head; B, profile view of right side of body (crack in the amber on the upper mesosoma and upper head level creating a mirror effect in the image); C, detail of anterior head showing clypeal lobes, and clypeal, mandibular and labral chaetae; D, dorsal view of head and mesosoma; E, dorsal view of gaster; F, meso- and metatibia and meso- and metabasitarsus, white asterisks at distal mesotibia and basal mesobasitarsus, white triangle points to tip of mesotibial spur; black asterisks and triangle the same positions in the hind leg. Scale bars are 0.2 mm in A, D, and E; 0.1 mm in C; and 0.5 mm in B.