Zigrasimecia boudinoti, 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 : 311-313

Zigrasimecia boudinoti Chaul, sp. nov.

( Fig. 6 )

Diagnosis (worker). Large species. Head roughly subrectangular (longer than wide) in full-face view. Body pilosity composed of abundant, relatively long, flexuous or erect, filiform setae. Dorsal mesosomal outline mildly convex; propodeum dorsal and posterior surfaces distinct, but not separated from one another by a strongly marked corner. In dorsal view, propodeal posterior margin pronounced laterally (medially concave). Petiolar node apex sharp, not forming a dorsal surface; tranversally the apex is bilobed.

Examined material. Holotype worker (ANTWEB1032623). Hukawng Valley , Kachin Province, Myanmar; Lower Cenomanian (ca.98.79 ± 0.62 Ma) [ CELC].

Description. Holotype worker. Measurements: HW 0.90, HL 0.99, EL 0.27, ON>150, MesL 1.1, MesH 0.79, PetAFL 0.45, Ptg3L 0.85, Ptg4L 0.50, TL 3.89. Head. In full-face view, lateral margins of head gently convex. Vertexal corners round, but well-defined, with clearly differentiated lateral and vertexal margins. Vertexal margin slightly concave ( Fig. 6 , A). Mandible dorsal margin apparently sinuous close to the apical tooth (difficult to confirm due to distortion of the amber piece in that position). Labrum and labio-maxillary complex including all palpomeres not visible at any angle. Clypeal anterior margin having around 34 chaetae. Clypeal lobe about twice the size of torular diameter. Clypeal middle longitudinal length smaller than lateral portions; epistomal sulcus touching the anteriormost portion of the toruli. Scrobe well-developed, formed by a sharply delimited frontal carina. Head, including compound eye's surface, and scape covered with simple, filiform, erect setae. Compound eye relatively large, with more than 150 ommatidia. Mesosoma. Overall, mesosoma not as compact as most species in the genus. In profile, dorsal outline of mesosoma mildly convex, abruptly descending into a steep, concave, posterior propodeal margin. Dorsal mesosoma sclerites fused, as usual for the genus, but feeble "waves" in the lateral mesosomal margins in dorsal view apparently indicate the limits of the pronotal, the "mesometanotal", and the propodeal areas. A soft depression that goes from one metanotal spiracle to the other likely indicates the anterior propodeal limit. Pronotum width 0.44 x head width. Lower and upper mesopleura and lower metapleura at least partially delimited by carinae. Metanotal spiracle distant from mesonotal spiracle about as much as it is from propodeal spiracle. Propodeal spiracle 0.09 mm (about 11% MesH), metanotal spiracle 0.11 mm ( Fig. 6. D ). Metapleural and propodeal lateral surfaces separated by a carina only on the lower portion. Posterior propodeal surface concave, its lateral margins well defined, subcarinated. Dorsal propodeal area merging into the propodeal lateral and posterior surfaces through soft curved corners. Protibia having a pair of simple spur-like setae next to the calcar, the latter with a poorly defined velum and bifid apically; mesotibial and metatibial smaller (anterior) spurs simple, mesotibial larger (posterior) spur barbulate apically; metatibial larger (posterior) spur pectinate. Larger metatibial spur clearly barbulate. Legs, dorsum of mesosoma, and corners of propodeal posterior surface covered with filiform setae similar to those on the head, but often longer. Dorsum of metacoxae posteriorly carinated. Tiny, pubescence-like, curved setae are present on dorsum of pronotum, mesometanotal, and propodeum, denser on the latter. Metasoma. Tip of petiolar node bilobed and thin, not forming a clear dorsal surface. Process of petiolar sternite well-developed, digitiform and anteriorly inclined. Prora in lateral view forming a sharp angle between ventral and anterior faces of first gaster sternite; in anterior view, V-shaped. A very mild cinctus likely present on A4, indicated by a curvature at the edge of A3 tergite which articulates on A4 pretergite. Dorsum of petiole and gaster covered on setae similar to those on the head and mesosoma. Tiny, curved setae are also present, sparse on gaster, except on fourth and fifth gaster tergites (AVI and AVII) where they are abundant.

Comments. This species is, together with Z. hoelldobleri , the largest in the genus (both being larger than the species known by queens, Fig. 14 ). Zigrasimecia boudinoti cannot be confused with Z. hoelldobleri by the radically different body setation. It shares the same type of setae as Z. chuyangsui , but the latter has a chubbier appearance, with a more compact and evenly curved mesosoma, and a round petiolar node apex rather than a thin bilobed one.

The specimen itself is superbly preserved, but the surrounding amber matrix is considerably dirt, which prevents the visualization of some features. There are mild distortions on the petiole anteriorly, where it articulates with the mesosoma, and posteriorly, where it articulates with A3; the node itself appears intact.

Etymology. The name is in honour of the great myrmecologist and friend Brendon Elias Boudinot. 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 6. Holotype of Zigrasimecia boudinoti (ANTWEB1032623). A, full-face view of the head; B, profile view of left side of body; C, right portion of anterior head, evincing clypeal lobe, and clypeal, mandibular and labral chaetae; D, profile of the right side of mesosoma with metanotal and propodeal spiracles indicated (mtsp and propsp) and propodeal spiracle magnified on the bottom right corner (under epifluorescence light); E, profile of right side of the head; F, dorsal view of the body. Scale bars are 0.2 mm in A, B, and F and 0.1 mm in C and E. Abbreviations: Umspl, upper mesopleuron; Lmspl, lower mesopleuron; Lmtpl, lower metapleuron; MesL, mesosoma length.

FIGURE 14. Relative body size comparison of all described species of Zigrasimecia (with morphospecies Zigrasimecia ufv-11 included, see Section 3.3 of text).