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

We first establish that we agree with a central concern of Dubovikoff & Zharkov [1] regarding the provenance of the army ant specimen we reported [2]. Indeed, the collection the authors note, housed within the Zoological Institute of the Russian Academy of Sciences (St Petersburg), is one of two collections we were made aware of shortly after the publication of our article. Although not mentioned in their reply, we were informed by one of the authors that the copal within this collection was initially dated as Baltic amber in the 1920s. This collection date was concerning as the specimen we reported, housed at the Museum of Comparative Zoology and labelled as Baltic amber, was included in a museum ledger from the 1930s. News of this historical collection at the Russian Academy of Sciences, as well as another in Germany from the same timeframe, prompted us to investigate the provenance of our reported specimen via Fourier-transform infrared (FTIR) spectroscopy. Our FTIR analyses indicated that the specimen we reported did not possess a unique spectroscopic characteristic of Baltic amber and was most likely subfossil resin (copal); these results constituted the basis of our retraction [3]. There is no doubt that the specimen is not Baltic amber; however, there are three elements that Dubovikoff & Zharkov raise that we feel are inaccurate and require a response in the literature [1]. These issues relate to the identification of copal specimens, CT-scan segmentation and repeatability, and the nature of taxonomic assignment.