Zigrasimecia ferox Perrichot, 2014

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 : 319

Zigrasimecia ferox Perrichot, 2014

( Fig. 11 )

Diagnosis (worker). Small species.Head subrectangular (longer than wide) in full-face view.Body pilosity composed of filiform, sparse, short, and erect setae. Dorsal mesosomal outline convex; propodeal dorsal and posterior surfaces separated by a strongly marked corner. Petiolar node with a distinct truncate dorsal surface. Cinctus on A4 present, mild.

Comments. All complete specimens from the type series of Z. ferox were originally syninclusions in the same piece of amber ( Perrichot, 2014). After treatment of the original piece, the holotype (JWJ-Bu18a in Perrichot, 2014, ANTWEB1008126-JWJ-hym18a on AntWeb webpage) and one paratype (JWJ-Bu18b in Perrichot, 2014, ANTWEB1008128-JWJ-hym-18b on AntWeb webpage) are still together in the same amber piece, while another paratype (JWJ-Bu 17 in Perrichot, 2014,ANTWEB1008127-JWJ-hym17 on Antweb webpage) is included in another piece. Curiously, at first look, the three specimens differ enough to raise suspicion about their conspecificity; however, that is just an impression, as their differences are almost certainly a result of the preservation. The holotype has a low bump on the dorsal mesosomal outline, at about the level of the metanotum or anterior portion of the propodeum ( Fig. 11 , A), as opposed to a continuous dorsal outline as seen in the paratypes, and its cuticle, especially on the head, looks overall a bit desiccated. Paratype ANTWEB1008128 differs from the holotype and the other paratype by having an acute apex of the petiolar node that barely forms a dorsal margin ( Fig. 11 , B), as opposed to a truncate top of the node, forming a clear dorsal margin in profile ( Fig. 11 , D and E). It also differs by the shape of the anterior surface of the A3 tergite (first gastral tergite), which is concave and projecting over the helcium, as opposed to a flat to slightly convex anterior surface. Paratype ANTWEB1008127 appears to have the best preservation among the type series, with only a small detachment of the metasoma between A3 and A4. These differences between the types are here interpreted as taphonomic effects. The mesosomal bump in the holotype is assumed to be an artifact, the true state for the species being the shape seen in the paratypes. The cinctus on A4, initially interpreted as possibly the result of poor preservation ( Perrichot, 2014), is here interpreted as a true feature of Z. ferox , since it is seen in the three complete specimens (although apparently weak in ANTWEB1008128), but especially because in paratype ANTWEB1008127, which has A3 disarticulating from A4, the formation of a distinct pretergite on A4, a typical result of cinctus formation in ants, is observed ( Fig. 11 , F). All that considered, as well as the diagnoses of the new species, Z. ferox can be differentiated from any other species in the genus by its new diagnosis presented above. The variation observed in the species treated in Cao et al. (2020b) is commented below, with some of the specimens studied in that work here considered as belonging to different species.

Figures

FIGURE 11. Type series of Zigrasimecia ferox. Putative taphonomic effects (A and B) and the corresponding states assumed to be true for the species (C and D). Black triangles in A and C point to the metanotum (or anterior propodeal) level, with holotype in A having a bump which could be an artifact of preservation. Black triangles in B and D indicate the apex of the petiole node, possibly artificially reduced by compression in B. Gray triangles in B and D indicate the anterior surface of A3 tergite, with the shelf-like projection in B being probably the result of folding of the sclerite in the taphonomic process. Cinctus on A4 (E and zoomed in F) is interpreted as a true feature of Z. ferox, not an artifact of preservation. In F, the white triangles show posterior edge of A3, black triangles indicate constriction on A4 (cinctus), which separates pre- and posttergites 4, and gray triangle shows swollen intersegmental membrane or internal liquid overflow.