New fossil ants in French Cretaceous amber (Hymenoptera: Formicidae)

Abstract

Recent studies on the ant phylogeny are mainly based on the molecular analyses of extant subfamilies and do not include the extinct, only Cretaceous subfamily Sphecomyrminae. However, the latter is of major importance for ant relationships, as it is considered the most basal subfamily. Therefore, each new discovery of a Mesozoic ant is of high interest for improving our understanding of their early history and basal relationships. In this paper, a new sphecomyrmine ant, allied to the Burmese amber genus Haidomyrmex, is described from mid-Cretaceous amber of France as Haidomyrmodes mammuthus gen. and sp. n. The diagnosis of the tribe Haidomyrmecini is emended based on the new type material, which includes a gyne (alate female) and two incomplete workers. The genus Sphecomyrmodes, hitherto known by a single species from Burmese amber, is also reported and a new species described as S. occidentalis sp. n. after two workers remarkably preserved in a single piece of Early Cenomanian French amber. The new fossils provide additional information on early ant diversity and relationships and demonstrate that the monophyly of the Sphecomyrminae, as currently defined, is still weakly supported.

Rediscovery of the Bizarre Cretaceous AntHaidomyrmexDlussky (Hymenoptera: Formicidae), with Two New Species

“…also, the size of the queen metasoma is relatively large in proportion to overall body size compared with that of workers due to flight muscles, but the metasoma in H. scimitarus is quite small. lastly, it is highly unlikely that the differences in pilosity as well as the proportions of the coxae, basal funicular articles, head capsule, and mandibles that are observed here are due to caste differentiation, since both workers and a gyne of H. mammuthus are known and the castes differed only in size and in minor aspects of mandibular morphology (Perrichot et al, 2007).…”

“…Perrichot et al (2007) reported the earliest fossil evidence for ant sociality (i.e., castes) in H. mammathus, after discovering both a gyne and two workers in the same deposit. as with all sphecomyrmines, both Haidomyrmex and Haidomyrmodes possess this shortened scape, and so while, again, there is no direct evidence for sociality in Haidomyrmex, there would appear to be none against it at this time.…”

“…First, while there is precious little data in the way of caste differentiation in Cretaceous ants, the one definitive conspecific description from Perrichot et al (2007) demonstrates that reproductives and workers are only slightly distinct morphologically in Haidomyrmodes mammathus-with only major differences in body size and measurements. in the case of H. zigrasi, mandibular morphology, propleuron shape, body size, petiole shape, and cuticular sculpturing are all distinctly different from H. scimitarus and H. cerberus.…”

“…a decade after H. cerberus was described, similar scythe-mandibled ants were discovered in ~100 myo French amber. These three partially preserved individuals, a gyne and two workers, were determined to be conspecific and described as the aforementioned Haidomyrmodes mammathus, demonstrating that this unusual scythiform morphology was not entirely uncommon (Perrichot et al, 2007). The morphological similarities between Haidomyrmodes and Haidomyrmex led to the placement H. mammathus in the tribe Haidomyrmecini, which Bolton (2003) first erected for Haidomyrmex.…”

A Phylogenetic Analysis of Ant Morphology (Hymenoptera: Formicidae) with Special Reference to the Poneromorph Subfamilies

“…Even then, the insertion of these fossils into a molecular-based phylogenetic tree has been achieved only indirectly by following the fossil's traditional taxonomic assignment rather than as a result of phylogenetic analysis combining both extinct and extant terminals. Clearly, the oldest known ant fossils, those currently classified into exclusively extinct taxa, have the potential to provide the best calibration points for deep nodes and thus increase the accuracy of divergence-time estimations for Formicidae (Perrichot et al, 2007b). Building a comprehensive morphological data set is thus the first step necessary for the incorporation of these diverse and important fossil ant faunas into the reconstruction of ant phylogeny.…”