Zigrasimecia

†Zigrasimecia Temporal range: Early Cenomanian, Late Cretaceous K Pa Eo Ol Mi Pl Burmese amber, Kachin State, Myanmar
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Zigrasimeciinae
Genus:	†Zigrasimecia Barden & Grimaldi, 2013
Type species
Zigrasimecia tonsora
Diversity
8 fossil species (Species Checklist)

A genus of iron maiden ants, a Formicidae stem lineage with bizarre mouthpart morphology.

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Identification

Keys including this Genus

• Key to genera of Zigrasimeciinae

 

Distribution

This taxon is known from Burmese amber, Kachin State, Myanmar (Early Cenomanian, Late Cretaceous).

Discussion

Cao et al. (2020) - Zigrasimecia was erected based on a single piece of Burmese (Myanmar) amber which contains a dealate gyne, designated as Zigrasimecia tonsora. The unique type specimen was only partially preserved, missing part of petiole and gaster, and details of the mouthparts were difficult to ascertain. The second species of this genus, Zigrasimecia ferox, was described based on the worker caste. Numerous features are shared between Z. ferox and Z. tonsora, although Perrichot (2014: p. 168) adduced a list of specific features which distinguish the two species. The unique morphology of Zigrasimecia is nowhere fully paralleled in the extant Formicidae, and is thought to represent habits that became extinct with the lineage (Barden & Grimaldi 2013).

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.

Castes

There is a diagnosis of this alate but it has not been assigned to a species.

Cao et al. 2020. Figure 3. Alate gyne of the unplaced Zigrasimecia, No. CNU-HYM-MA2019055; scale bars for (A), (B) = 0.5mm, for (C) = 0.2mm, and for (D) - (E) = 0.5mm. (A), Photograph of alate gyne in lateral view, (B), reconstructive drawing of alate gyne, (C), head of alate gyne in dorsal view, (D) and (E), venation reconstructions, where (D), indicates cells and (E), indicates veins.

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

• †ZIGRASIMECIA [†Zigrasimeciinae]
  • †Zigrasimecia Barden & Grimaldi, 2013: 407. Type-species: †Zigrasimecia tonsora, by original designation.

Taxonomic history

• †Zigrasimecia in †Sphecomyrminae: Barden & Grimaldi, 2013: 410.
• †Zigrasimecia in †Sphecomyrminae, †Sphecomyrmini: Perrichot, 2014: 166.
• †Zigrasimecia in †Sphecomyrminae, †Zigrasimeciini: Borysenko, 2017: 18.
• †Zigrasimecia as genus: all authors.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Cao et al. (2020) - Emended diagnosis (female): Distinguished from both Boltonimecia and Protozigrasimecia as outlined in the key above. Sharing uniquely with Protozigrasimecia the large, dome-shaped head with deep and broadly concave occiput in posterior view, and evenly and broadly concave, arcuate clypeus. Additional definition provided by the following characters: antenna of worker and alate gyne 12-merous (see Note 5); worker body length 1.8 - 4.6 mm, gyne body length 2.7 - 4.0 mm; head massive, nearly as large as mesosoma; frontal carinae present; clypeus in form of an evenly arched transverse bar; anterior margin concave with dozens of denticulate traction setae; labrum with dense spiniform traction setae; inner surface of mandibles with traction setae distributed along their length; worker eyes small and rounded; scape at least twice length of pedicel; labrum covered with erect and strong spiniform traction setae; labrum apicomedially bilobate; mesosoma strongly convex and anteroposteriorly compact, without external indication of segmental articulation; helcium (= articulatory sclerites of abdominal segment III) axial (situated at segment midheight). Gyne: most of characters similar with workers, except for the following: eyes reniform; mesoscutum and mesoscutellum demarcated by sulcus; mesosoma musculated for flight; forewing with seven closed cells: the costal, two submarginal, one marginal, the basal, subbasal, and first discal.

Note 6: The antennomere counts of alate Boltonimecia and Protozigrasimecia are unknown.

Note 7: The coronal rugosities described on the vertexal area of the holotype of Z. tonsora are almost certainly artefacts derived from the taphonomic process (BEB, pers. obs., American Museum of Natural History). The rugosities are asymmetrical, and similar apparent bubble streaks can be observed on other, distantly related taxa.

References

• Barden, P. & Grimaldi, D. 2013. A new genus of highly specialized ants in Cretaceous Burmese Amber (Hymenoptera: Formicidae). Zootaxa 3681, 405-412 (doi:10.11646/zootaxa.3681.4.5).
• Barden, P. 2017. Fossil ants (Hymenoptera: Formicidae): ancient diversity and the rise of modern lineages. Myrmecological News 24: 1-30.
• Borysenko, L.H. 2017. Description of a new genus of primitive ants from Canadian amber, with the study of relationships between stem- and crown-group ants (Hymenoptera: Formicidae). Insecta Mundi 570: 1–57.
• Boudinot, B.E., Perrichot, V., Chaul, J.C.M. 2020. †Camelosphecia gen. nov., lost ant-wasp intermediates from the mid-Cretaceous (Hymenoptera, Formicoidea). ZooKeys 1005, 21–55 (doi:10.3897/zookeys.1005.57629).
• Boudinot, B.E., Richter, A., Katzke, J., Chaul, J.C.M., Keller, R.A., Economo, E.P., Beutel, R.G., Yamamoto, S. 2022. Evidence for the evolution of eusociality in stem ants and a systematic revision of †Gerontoformica (Hymenoptera: Formicidae). Zoological Journal of the Linnean Society XX:1-35 (doi:10.1093/zoolinnean/zlab097/6523228).
• Cao, H., Boudinot, B.E., Shih, C., Ren, D., Gao, T. 2020. Cretaceous ants shed new light on the origins of worker polymorphism. Science China Life Science 63, 1-4 (doi:10.1007/s11427-019-1617-4).
• Perrichot, V. 2014. A new species of the Cretaceous ant Zigrasimecia based on the worker caste reveals placement of the genus in the Sphecomyrminae (Hymenoptera: Formicidae). Myrmecological News 19, 165-169.
• Richter, A., Boudinot, B., Yamamoto, S., Katzke, J., Beutel, R. G. 2022. The first reconstruction of the head anatomy of a Cretaceous insect, †Gerontoformica gracilis (Hymenoptera: Formicidae), and the early evolution of ants. Insect Systematics and Diversity 6(5): 1-80 (doi:10.1093/isd/ixac013).
• Zhuang, Y., Xu, W., Zhang, G., Mai, H., Li, X., He, H., Ran, H., Liu, Y. 2022. Unparalleled details of soft tissues in a Cretaceous ant. BMC Ecology and Evolution, 22: 146 (doi:10.1186/s12862-022-02099-2).