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| Vulcanidris cratensis Lepeco, Brandão & Camacho, in Lepeco, Meira, Matielo, Brandão et Camacho, 2025. |
Highlights:
• A new ant fossil is described from the Brazilian Crato Formation
• Micro-computed tomography supports its identity as a hell ant
• Ants spread through global ecosystems earlier than once believed
• The new finding represents the earliest undisputed ant known to science
Summary
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. The so-called hell ants of the subfamily Haidomyrmecinae comprise a group of morphologically unique ants exclusive to the Cretaceous. They represent some of the earliest known ants in the fossil record, preserved as amber inclusions in deposits in France, Myanmar, and Canada. 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.
Keywords: micro-computed tomography, fossil ants, Haidomyrmecinae, Hymenoptera, Formicidae, Crato Formation, Aptian
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| Habitus of Vulcanidris cratensis gen. et sp. nov. Holotype (MZSP-CRA-0002). Scale bar, 2 mm. |
Systematic paleontology
Order Hymenoptera Linnaeus, 1758.
Family Formicidae Latreille, 1802.
Subfamily Haidomyrmecinae Bolton, 2003.
Genus Vulcanidris Lepeco, Brandão and Camacho gen. nov.
Etymology: The genus name honors the family Vulcano, including Maria Aparecida Vulcano, who has assembled a very important Crato collection bearing her name, recently donated to MZSP. The genus name has the Greek word “idris” as a suffix, meaning “the provident one” (i.e., an ant), which has often been used for naming ant genera.
Diagnosis: The new genus can be confidently placed in Formicoidea by the possession of a prognathous head (Figure 1); elongated scape, which is nearly as long as the remainder of the antenna (Figure 2A); small meso- and metacoxal cavities (Figure 3E, right arrowheads); base of protrochanter strongly constricted, curved, and partially concealed by disticoxa (Figure 3E, left arrowhead); radial cell not produced distally (Figure 2C, left arrowhead); well-developed subpetiolar process (Figure 3F); petiole constricted posteriorly (Figure 2F); and second metasomal segment constricted on articulation with the third one (Figure 2G). Vulcanidris gen. nov. is placed among the Haidomyrmecinae based on the presence of a facial projection coupled with mandibles that articulate ventrally on the head (Figures 3B–3D). The new genus closely resembles Aquilomyrmex but can be differentiated by the presence of a slight constriction on the clypeal projection at level of antennal insertions (Figure 2E, lower arrowhead); forewing with three submarginal cells, vein 3r-m tubular (Figure 2C, right arrowhead); and body relatively less slender than Aquilomyrmex. Tomography reconstructions also indicate the presence of a tooth on the inner margin of the mandibles (Figures 3B and 3D), which could not be fully confirmed due to preservation. Finally, Vulcanidris gen. nov. can be differentiated from Cariridris33 by the head expanded laterally, smaller compound eyes, and larger body size.
Vulcanidris cratensis Lepeco, Brandão and Camacho sp. nov
Type material: Holotype is a female (MZSP-CRA-0002) from the Aptian (Lower Cretaceous) Crato Formation in northeastern Brazil. See STAR Methods for a complete description.
Etymology: The specific epithet refers to the Crato Formation, the Brazilian geological deposit where the new species was discovered.
Diagnosis: Head with compound eyes positioned anteriorly; elongated posterad, expanded laterally beyond the lateral level of the compound eyes; clypeal projection relatively long, extending anteriorly from between the compound eyes; ventral surface laterally with short, stiff setae (Figure 2E, upper arrowhead); antennae inserted anterior to the compound eyes; scape elongated; legs with femora swollen proximally, tapering progressively distally, and expanded at the articulations with the tibiae; forewing with strongly curved 2Rs (Figure 2D); large size, only known alate female measuring approximately 13.5 mm in length.
Anderson Lepeco, Odair M. Meira, Diego M. Matielo, Carlos R.F. Brandão and Gabriela P. Camacho. 2025. A Hell Ant from the Lower Cretaceous of Brazil. Current Biology. DOI: doi.org/10.1016/j.cub.2025.03.023 [April 24, 2025]