Gerontoformica gracilis

†Gerontoformica gracilis 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. gracilis
Binomial name
†Gerontoformica gracilis (Barden & Grimaldi, 2014)

Zhuang et al. (2025) report the first syninclusion of winged and wingless conspecific female ants of one of the four stem group ant subfamilies, †Brownimeciinae, †Haidomyrmecinae, †Sphecomyrminae and †Zigrasimeciinae.

Photo Gallery

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  Zhuang et al. (2025), Fig. 3: Fossil colony of †Gerontoformica gracilis. (A) General view of the fossilized colony fragment of †Gerontoformica gracilis, specimen LYU-BM2005; red arrows indicate workers and blue arrow indicates the queen. (B, C) Workers in detailed dorsal and frontal views, respectively. (D, E) The queen in detailed dorsolateral views. Scale bars, A = 2 mm; B - E = 0.5 mm.

Identification

Zhuang et al. (2025) - Queen: Identifiable as for the worker (see Boudinot & al. 2022a). Compound eye oval-shaped and slightly convex. Scape stout and short, trapezoidal in lateral view. Pedicel elongate and slender, antennomeres III - XII slowly widening in order. Pronotum somewhat elongate. Mesoscutum short and flattened. Petiole long; subpetiolar process small and rounded. Abdominal segment III subtriangular in lateral view; abdominal segment IV most developed and about 3 / 4 as long as wide.

Distribution

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

Castes

  X-ray micro-CT scan 3D model of Gerontoformica gracilis (worker) prepared by the Economo lab at OIST.

This is a 3D model of a fossilized ant first presented in the scientific article ‘Evidence for the evolution of eusociality in stem ants and a systematic revision of †Gerontoformica (Hymenoptera: Formicidae)’ published in the Zoological Journal of the Linnean Society by Brendon E. Boudinot and others. The ant was identified and described as Gerontoformica gracilis from a piece of Cretaceous amber about 99 million years old (collection ID: AMNH Bu-SY23; specimen ID: CASENT0741232). To create the 3D model, the amber was micro-CT scanned. Adrian Richter created the model using segmentation techniques, Shuhei Yamamoto took the photo, and Julian Katzke scanned it and uploaded it to Sketchfab. See on Sketchfab. See list of 3D images.

Nomenclature

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

• †gracilis. †Sphecomyrmodes gracilis Barden & Grimaldi, 2014: 4, figs. 2A-C, 10B, 11C, 11D (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: 18, 27 (redescription, in key).

Type Material

• Type locality and stratigraphy: Hukawng Valley, Kachin Province, northern Myanmar. Upper Cretaceous, lower Cenomanian (ca. 98.79 ± 0.62 Ma; Shi & al. 2012). Housed at the Institute of Geology and Paleontology at Linyi University, Linyi, China.

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.1005.57629).
• 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).
• Perfilieva, K.S. 2023. Cretaceous-Burmese-amber ants: Morphological features and community structure. Biology Bulletin Reviews 131, 38–54 (doi:10.1134/s207908642301005x).
• 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., Perrichot, V., Li, J., Zhuo, D., Liu, Y., Wang, B., Zhang, Q., Boudinot, B.E. 2025. Systematics and early evolution of ants (Hymenoptera: Formicidae): the first male and worker-queen association for †Gerontoformica. Myrmecological News 35: 89-98 (doi:10.25849/MYRMECOL.NEWS_035:089).