Zigrasimecia, Barden & Grimaldi, 2013

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 : 305-306

Key to the females of Zigrasimecia

Notes: Z. tonsora and Z. goldingot , described based on queens, are tentatively included in the key based on their head and metasomal characters. Any mesosomal character mentioned in the key must not be considered if the keyed specimen is a queen.

1. The specimen is a gyne: mesosoma is complex, having discernible mesoscutum and mesoscutellum and clear divisions between the sclerites......................................................................................... 2

- The specimen is a worker: mesosoma is compact and simplified, most sclerites are fused and indiscernible.............. 3

2. [Triplet] With the following combination of characters: More than 30 clypeal chaetae. Petiole having a distinct anterior, dorsal, and posterior surfaces; dorsal surface appearing flat ( Fig. 1 , B of Barden & Grimaldi, 2013). Head having short, fine setae on frons and vertex which are progressively longer posterad. Frons with a V-shaped shallow groove. Propodeum dorsal surface long ( Fig. 2 , A and B of Barden and Grimaldi, 2013)........................... Z. tonsora Barden & Grimaldi, 2013

- With the following combination of characters: Less than 25 clypeal chaetae. Petiole node apex brief, not forming a distinct dorsal surface. In anterolateral (or posterolateral) views of the petiole, apex of node bilobed. Setation on body mostly of decumbent small setae. Frons without grooves. Propodeum dorsal surface short (micro-CT scan image by Yuhui Zhuang available at Antweb under specimen YKLP-AMB-001)............................. Z. goldingot Zhuang et al., 2022

- Without the above two combinations. From now on, run your queen specimen in the key without considering mesosomal characters whenever mentioned......................................................................... 3

3. Abundant and conspicuous standing setae on dorsum of head, mesosoma, and metasoma. Setae varying in morphology ( Figs. 6 , 8 , 11 )............................................................................................ 4

- Conspicuous standing setae on body absent or restricted to dorsum of head. Body mainly glabrous, at most covered by very small, appressed, setae ( Figs. 7 , 8 , 12 , 13 )................................................................. 7

4. Standing setae on body thin and filiform ( Figs. 6 , 9)......................................................... 5

- Standing setae on body thick, tip of individual seta truncate and sometimes slightly clavate ( Fig. 14 ).............................................................................................. Z. hoelldobleri Cao e t al., 2020

5. Setae on body sparse, relatively short, erect (not flexuous). Tip of petiolar node truncate. Cinctus on abdominal segment IV weak, but discernible ( Fig. 11 )....................................................... Z. ferox Perrichot, 2014

- Setae on body flexuous and relatively long, usually abundant. Tip of petiolar node either round and without paired protrusions ( Fig. 10 , D) or thin (barely forming a dorsal surface) and with a pair of protrusions ( Fig. 6 D ). Cinctus on abdominal segment IV vestigial to absent.................................................................................. 6

6. Mesosoma extremely compact, "chubby". Frontal carina vestigial, merely a soft oblique bump between the torulus and the eye. Tip of petiolar node round. Head in full-face view round, with poorly differentiated lateral and vertexal margins. Eyes with less than 100 ommatidia (Fig. 9).......................................................... Z. chuyangsui sp. nov.

- Mesosoma not particularly compact. Frontal carina conspicuous. Tip of petiolar node with a pair of protrusions. Head in full-face view subrectangular, having distinct lateral and vertexal margins. Eyes with more than 150 ommatidia ( Fig. 6 )........................................................................................... Z. boudinoti sp. nov.

7. Dorsum of head, at the frontal and vertexal areas, with a conspicuous patch of setae which can be raised and long, and flagellate or short, decumbent and curved.......................................................................... 8

- Dorsum of head without a patch of specialized setae......................................................... 9

8. Long, subflagellate, looped setae on dorsum of head. Head in full-face view almost as long as broad ( Fig.13 )................................................................................................... Z. thate sp. nov.

- Short, curved, and decumbent setae on dorsum of head. Head in full-face view slightly longer than wide ( Fig. 20 )............................................................................................. Zigrasimecia ufv-11

9. Head in full-face view subrectangular. In profile, propodeal dorsal and posterior (descending) margins distinct. Medium-sized species (TL 2.86) ( Fig. 12 ).............................................................. Z. perrichoti sp. nov.

- Head in full-face view round. In profile, propodeal dorsal and posterior (descending) margins softly merge into each other. Small species (TL 2.25) ( Fig. 7 )........................................................ Z. caohuijiae sp. nov.

Figures

FIGURE 1. Schematic drawings of most of the measurements taken from the specimens (presented in the species descriptions or in Appendix 1). See Materials and Methods or Appendix 1 for a detailed explanation of the measurements. Codes: a, head length; b, head length 2; c, head width; d, head width 2; e, head width 3; f, head maximum depth; g, mesosoma length (see also Fig.6); h, mesosoma height; i, propodeal spiracle length; j, petiole anterior face length; k, posttergite 3 length; o, posttergite 4 length. Measurements a, g, j, k, and o summed equal total length (TL). Gaster measurements l, m, n, and p are additional metasomal measurements that are useful if the measurements k and o are blocked (see Appendix 1).

FIGURE 2. Masticatory margin of mandible in Gerontoformica and Zigrasimecia. A, Gerontoformica sp. (ANTWEB1032629); B, Z. ferox (ANTWEB1008126); C, Z. chuyangsui (ANTWEB1032660); D, Z. tonsora (ANTWEB11008098). Black triangles indicate incision between apical and basal teeth (or basal lamella). Image of Z. tonsora by Philip Barden and image of Z. ferox by Vincent Perrichot, courtesy of Antweb.org.

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 7. Holotype of Zigrasimecia caohuijiae (ANTWEB1041055). A, full-face view of the head (view of anterior portion blocked by an insect antenna and bubbles); B, profile view of right side of body; C, ventrolateral view of anterior portion of head; D and F, anterior view of head, with a full view of dorsal surface of mandibles, F is under epifluorescence; E, dorsal view of the body; G and H, Detail of mesosoma under different types of epifluorescence. Scale bars are 0.2 mm inA, B and E and 0.1 mm in C and D. Black triangles point to the labral medial lobes (laterally to the median lobes in D a pair of protuberances which are likely the hypostomal teeth).Abbreviations: cllb, clypeal lobe; dsm, dorsal surface of mandible; Lmspl, lower mesopleuron; Lmtpl, lower metapleuron; sp, spiracle; Umspl, upper mesopleuron; vsm, ventral surface of mandible.

FIGURE 8. Holotype of Zigrasimecia caohuijiae (ANTWEB1041055). A, dorsal view of mesosoma and petiole; B, detail of the right side of the petiole in profile, white triangle indicates the edge of the sclerite (posterior petiole tube or collar); C, zooming of pronotum in dorsal view under epifluorescent light, black triangles in A and C indicate minute decumbent setae on mesosoma (setae also clear in image D); D, zooming of propodeum and petiole under epifluorescent light; E, posterolateral view of propodeum, black triangle indicates hypertrophied propodeal spiracle; F, detail of probasitarsus, showing concentration of long, fine setae, white triangle indicates calcar with simple tip (not bifid), and black triangle indicates mesopretarsal claws with toothed inner margins; G, inner face of protibia and probasitarsus, showing two spur-like setae next to calcar; H, detail of abdominal segment VII and sting, black triangles show gonostyli. Scale bars are 0.1 mm.

FIGURE 10. Holotype of Zigrasimecia chuyangsui (ANTWEB1032660). A, zooming of anterodorsal view of head, showing mouthparts, black triangles from top to bottom point to clypeal, labral, and mandible chaetae; B, 6-segmented right maxillary palp; C, left protarsus, black triangle points to tip (bifid) of protibial calcar; D and E, dorsal and lateral zooming of petiole obscured by bubbles, black triangles in D indicate posterior margin of petiole node and in E indicates tip of subpetiolar process. Abbreviations: b1 and b2, bubbles; nd, petiole node; pmx1–pmx6, maxillary palpomeres 1–6; ppd, propodeum; t3, tergum of abdominal segment 3 (first gaster tergite).

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.

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.

FIGURE 13. Holotype of Zigrasimecia thate (ANTWEB1038912). A, full-face view of the head, black triangles indicate mandible dorsal setae; B, profile view of left side of body; C, anterior view of the head; D, dorsal view of the body; E, zoom of flagelliform setae on frons and vertex (same view as C); F, detail of mesosomal profile. Abbreviations: Lmspl, lower mesopleuron; Lmtpl, lower metapleuron; mgo, metapleural gland opening; Ppd, propodeum; Prn, pronotum; sp, spiracles (metanotal and propodeal); Umspl, upper mesopleuron. Scale bars are 0.2 mm in B and D, and 0.1 mm in A.

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

FIGURE 20. Morphospecies Zigrasimecia ufv-11. A and B, head in full-face and anterior views, respectively, of specimen ANTWEB1047053, black triangle indicates curved, decumbent setae on frons and vertex; C, profile view of right side of body of specimen ANTWEB1047903. Scale bar 0.2 mm in A, and 0.5 mm in C.