Gerontoformica subcuspis

†Gerontoformica subcuspis 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:	Sphecomyrminae
Tribe:	Sphecomyrmini
Genus:	Gerontoformica
Species group:	gracilis
Species:	†G. subcuspis
Binomial name
†Gerontoformica subcuspis (Barden & Grimaldi, 2014)

Identification

Boudinot et al. (2022) - †Gerontoformica spiralis and †G. subcuspis were difficult to separate in the present study based on the available anatomical evidence and may be conspecific. Specifically, we observe that, in addition to conditions outlined in the key (see that section below), the two species are highly similar in the following conditions, which we only roughly characterize here:

1. proportions and fine details of the head, including frontal carina shape
2. the degree of mesonotal, metanotal and propodeal convexity
3. the width of separation between the meso- and metanota plus metanotum and propodeum
4. the shape and proportions of the petiolar node
5. the form of the third abdominal (first ‘gastral’) segment

It is possible that †G. spiralis and †G. subcuspis represent the smaller and larger ranges of body size of a single species, with the former reported to have a total body length of 4.22–5.22 mm and the latter 5.35–5.76 mm (Barden & Grimaldi, 2014). Our focal uncertainties relate to the shapes and setational patterns of the tarsi of †G. subcuspis, and the form of the subpetiolar process and prora of †G. spiralis. A potential feature separating the two species is the distance of the toruli from the posterior clypeal margin, which appears to be narrower in †G. spiralis relative to †G. subcuspis, but this could be a visual artefact caused by the apparent light distortion in the holotype image of †G. spiralis. We recommend further re-evaluation of these two species, ideally using µ-CT and additional light photography to resolve the uncertainties of the tarsi, toruli and sternal processes of the metasoma.

Distribution

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

Nomenclature

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

• †subcuspis. †Sphecomyrmodes subcuspis Barden & Grimaldi, 2014: 17, fig. 8A-C (w.) BURMESE AMBER (Myanmar, Cretaceous).
  • Combination in †Gerontoformica: Barden & Grimaldi, 2016: in supplemental information (not paginated).
  • Status as species: Barden, 2017: 3; Boudinot, Richter, Katzke, et al. 2022: 27 (in key).

References

• Barden, P. & Grimaldi, D. 2014. A diverse ant fauna from the mid-Cretaceous of Myanmar (Hymenoptera: Formicidae). PLoS ONE 9(4): e93627.
• Barden, P. & Grimaldi, D.A. 2016. Adaptive radiation in socially advanced stem-group ants from the Cretaceous. Current Biology 26: 515-521 (doi:10.1016/j.cub.2015.12.060).
• Barden, P. 2017. Fossil ants (Hymenoptera: Formicidae): ancient diversity and the rise of modern lineages. Myrmecological News 24: 1-30.
• 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.*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:[https://doi.org/10.1093%2Fzoolinnean%2Fzlab097%2F6523228 10.1093/zoolinnean/zlab097/6523228).

57629]).

• Perfilieva, K.S. 2023. Cretaceous-Burmese-amber ants: Morphological features and community structure. Biology Bulletin Reviews 131, 38–54 (doi:10.1134/s207908642301005x).