RETRACTED: An Eocene army ant

Abstract

Among social insects, army ants are exceptional in their voracious coordinated predation, nomadic life history and highly specialized wingless queens: the synthesis of these remarkable traits is referred to as the army ant syndrome. Despite molecular evidence that the army ant syndrome evolved twice during the mid-Cenozoic, once in the Neotropics and once in the Afrotropics, fossil army ants are markedly scarce, comprising a single known species from the Caribbean 16 Ma. Here we report the oldest army ant fossil and the first from the Eastern Hemisphere (EH), Dissimulodorylus perseus , preserved in Baltic amber dated to the Eocene. Using a combined morphological and molecular ultra conserved elements dataset spanning doryline lineages, we find that D. perseus is nested among extant EH army ants with affinities to Dorylus. Army ants are characterized by limited extant diversification throughout most of the Cenozoic; the discovery of D. perseus suggests an unexpected diversity of now-extinct army ant lineages in the Cenozoic, some of which were present in Continental Europe.

A Comment on: An Eocene army ant (2022) by Sosiak CE et al .

“…And as a result, we obtain a complete three-dimensional model that we can use to study all the necessary characters of the specimen. By applying the approach mentioned above and based on the initial data by microtomographic scanning, kindly provided by authors [2], we have obtained a full model reflecting the true structure of the described specimen (figures 1 e , 2) [4,5]. A comparison of the authors' results with the ones we obtained based on their initial data is presented in figure 1 d,e .…”

“…( a–c ) Specimens of the Dorylus nigricans from the African sub-fossilized resin (collection of the Zoological Institute RAS). Micro-CT reconstructions of the specimen PALE-8463, in ( d ) based on a three-dimensional model made by Sosiak et al [2] and ( e ) our results of volumetric rendering of the same specimen. Colours in blue scale are indicated 'void space' and yellow-green tones ‘dense’ areas.…”

“…As for the described species, based on the features we have studied long scapes and antennae in general, the structure of the mesosoma (promesonotal suture well defined and with deep impression (from lateral view) and the shape of the pygidium), we believe that this species belongs to the nigricans group. Summing up, we believe that the army ant described by Sosiak et al [1] as the fossil can actually be attributed to the extant species Dorylus nigricans Illiger, 1802 (= Dissimulodorylus perseus, syn. nov. ) encapsulated within the sub-fossilized resin.…”

An Invited Reply to: A Comment on: An Eocene army ant (2022) by Sosiak CE et al .

“…This stark difference allows for a clear delineation that allows for a conservative and, importantly, repeatable segmentation process. Using the published Z-stack slices from Sosiak et al [2], Dubovikoff & Zharkov generated what they term a 'complete' or 'full model reflecting the true structure of the described specimen'. There is no question that they presented more features in their final segmentation; however, the authors indicate that this was done by manually segmenting the scan (i.e.…”

Retraction: An Eocene army ant

“…Shortly after the publication of this report the authors were contacted independently by two researchers (Brendon E. Boudinot, The University of Jena and Dmitry A. Dubovikoff, St Petersburg State University). Both researchers indicated that they were aware of several specimens of Dorylus preserved in sub-fossil resin (copal), within historical collections of Baltic amber from 1920 to 1930s—the same time frame associated with the Museum of Comparative Zoology (MCZ) specimen reported in Sosiak et al [ 1 ]. Copal in both cases were either initially misidentified or mixed among pieces of authentic Baltic amber.…”