A hell ant from the Lower Cretaceous of Brazil

Modern ants are among the most ecologically dominant animal groups on Earth, with their diversity shaped by global events occurring since their origin in the late Mesozoic.^1,2,3 The so-called hell ants of the subfamily Haidomyrmecinae comprise a group of morphologically unique ants exclusive to the Cretaceous.⁴ They represent some of the earliest known ants in the fossil record, preserved as amber inclusions in deposits in France, Myanmar, and Canada.^5,6,7,8,9 Here, we report the oldest known Haidomyrmecinae, preserved as a rock impression in limestone of the Crato Konservat-Lagerstätte in northeastern Brazil. This finding also represents the earliest undisputed ant known to science. Micro-computed tomography applied to phylogenetic analysis of early ants shows that the new species is closely related to hell ants found only in Burmese amber. The presence of hell ants in the Aptian of northeastern Brazil provides the earliest evidence of Formicidae biogeographic history through deep time. The distribution of known clades indicates that hell ants were widely distributed, with repeated interchanges between Cretaceous landmasses. Notably, northeastern Brazil's paleoenvironment contrasts with other known deposits for Haidomyrmecinae, suggesting ecological diversity among these ants. Hell ants thrived for a long time in gymnosperm-dominated and mixed landscapes, such as the Crato paleoenvironment, persisting into the angiosperm expansion before being decisively affected by geological events toward the Cretaceous end.