Sphecomyrmodes
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Gerontoformica Temporal range: Late Albian to Early Cenomanian |
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| Gerontoformica cretacica holotype | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Hymenoptera |
| Family: | Formicidae |
| Subfamily: | incertae sedis |
| Genus: |
†Gerontoformica Nel & Perrault, 2004 |
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Gerontoformica is an extinct genus of stem-group ants. The genus contains thirteen described species known from Late Cretaceous fossils found in Asia and Europe. The species were described between 2004 and 2016, with a number of the species formerly being placed into the junior synonym genus Sphecomyrmodes.
Gerontoformica is known from over thirty adult fossil specimens which are composed of complete adult female workers and queens. The first fossil was discovered preserved as an inclusion in a transparent chunk of Charentese amber. The amber is thought to have been formed from resins of the extinct Pinales tree family Cheirolepidiaceae and possibly from the living family Araucariaceae. Paleoecology of the ambers indicates the shore to mangrove type forests were of a subtropical to warm temperate climate, with occasional dry periods The ambers are recovered from deposits exposed in quarries, road constructions, and beach exposures in the Charente-Maritime region of coastal France, notably at Archingeay. Dating of the amber has been done through pollen analysis and it is generally accepted to be approximately 100 million years old.
The majority of described fossils have been found and described from Burmese amber. The Asian specimens were recovered from unspecified deposits in the Hukawng Valley of Kachin State, Myanmar. Burmese amber has been radiometrically dated using U-Pb isotopes, yielding an age of approximately 99 million years old, close to the boundary between the Aptian and Cenomanian. The amber is suggested to have formed in a tropical environment around 5° north latitude and the resin to have been produced by either an Araucariaceae or Cupressaceae species tree.
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