Termite (Insecta: Isoptera) nest ichnofossils from the upper triassic chinle formation, petrified forest national park, Arizona

A fossil nest (calie), including chambers and galleries (runaways), from the lower part of the Petrified Forest Member of the Upper Triassic Chinle Formation in Petrified Forest National Park, Arizona, is similar to nests constructed by modern primitive termites (Insecta: Isoptera), which reflect cooperation in nest construction typical of complex social behavior. A new ichnogenus and ichno‐species, Archeoentomichnus metapolypholeos, is proposed for the distinctive ichnofossil that may represent the efforts of a social caste system in primitive termites. The Late Triassic (Late Carnian) nest also may represent the earliest known fossil evidence of Isoptera (termites) and is suggestive of the antiquity of social behavior among insects. Social behavior in insects, including termites, was previously thought to have evolved in the Early Cretaceous in conjunction with the evolutionary radiation of angiosperms.

Because the fossil and ichnofossil record of insects and organisms suggested to be insects dates back to the Late Ordovician and Early Silurian, and termite‐like ancestors (cockroaches?) are documented in the Carboniferous, it is possible that social behavior existed in primitive termites as early as the Paleozoic. Social insect nests of this antiquity are an important addition to the fossil record because they record an early example of exceptional social behavior, and because they exhibit a complexity of architecture that is exclusively unique to continental environments. Social insect nests like those constructed by termites and other insect ichnofossils are very distinctive and serve as evidence for the presence of insects even without a body fossil record.

Key words:

• Triassic
• termite nests
• insect
• social behavior
• Chinle Formation
• paleoecology
• paleohydrology
• insect evolution