Ancient ant colony and male fossil unveil evolutionary secrets in 99-million-year-old amber

In their study published today in Myrmecological News, Zhuang et al. revealed two extraordinary fossils preserved in 99-million-year-old Burmese amber. These findings shed fresh light on the early evolution of ants and their colonial lifestyles. Among the discoveries is the first-ever male specimen of the extinct ant genus Gerontoformica and the oldest direct evidence of queen-worker coexistence in a single fossil – both offering unprecedented insights into the social structure of ancient ants.

A Photoblog contribution by Yuhui Zhuang, photographed at Géosciences Rennes, University Rennes I.

Edit by Purbayan Ghosh and Salvatore Brunetti

Our key findings:

1. A rare male ant fossil: The newly described species, Gerontoformica priapos, marks the first confidently identified male of the stem ant subfamily Sphecomyrminae. The male’s exceptionally preserved genitalia, kidney-shaped compound eyes, and distinctive wing venation offer critical clues about early ant evolution and sexual dimorphism. Often referred to as the “forgotten caste” due to their scarcity in the fossil record, these males are vital for understanding reproductive strategies and species diversity.
   
2. Queen-worker association: In what we think is an exciting first, we documented a fossilized ant colony fragment that includes both a wingless worker and a winged queen (Gerontoformica gracilis) encased in the same piece of amber. This discovery confirms that early ants, like their modern counterparts, had already developed a division of labor between reproductive queens and non-reproductive workers – a defining trait of advanced social behavior.

Why we think this matters:
Today, ants dominate terrestrial ecosystems, yet their early evolutionary history has long been shrouded in mystery. These mid-Cretaceous fossils help bridge critical gaps in our understanding of how ant societies evolved. The male’s distinct anatomy challenges long-held assumptions about sexual dimorphism in stem ants, while the queen-worker pairing provides direct evidence of caste differentiation-occurring a staggering 40 million years before the emergence of modern ants.

Technical breakthroughs:
Using advanced imaging techniques, the team reconstructed detailed 3D models of the ants’ delicate structures-including wing veins and genitalia. This allowed precise comparisons with both extinct and living species, confirming Gerontoformica’s position on the ant evolutionary tree.

Future implications:
This study underscores the importance of male fossils in paleontology, which are often overlooked due to their stark morphological differences from females. We and probably others are now eager to uncover more male specimens, aiming to refine evolutionary timelines and explore how environmental changes shaped ant biodiversity following the Cretaceous-Paleogene extinction.