Temporal range: Bartonian, Middle to Late Eocene Baltic amber, Baltic Sea region
This taxon was described from Baltic amber (Bartonian, Middle to Late Eocene).
The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.
- †cordata. †Formica cordata Holl, 1829: 140 (s.) BALTIC AMBER (Eocene).
- Combination in Pheidole: Mayr, 1868c: 17.
- Incertae sedis in Myrmicinae: Casadei-Ferreira, Chaul & Feitosa, 2019: 123.
- [This ant is noted and figured in Schweigger, 1819: 119, pl. 18, fig. 70, but is not named.]
Casadei-Ferreira, Chaul & Feitosa, 2019: Among the extinct species of Pheidole, the most dubious fossil is †P. cordata. Its first record in the literature is Schweigger (1819). In this work, the author listed fossils from Baltic amber and described informally and illustrated an ant with a remarkably large head, showing triangular projections on the propodeum. These projections can be interpreted as propodeal spines or teeth. However, Schweigger did not name this specimen, and some years later, Holl (1829: 140) named it as †Formica cordata, using the same characters as Schweigger.
Mayr (1868) transferred it to Pheidole (Mayr 1868), even though he believed that Schweigger’s sketch was not clear and Holl’s description was somewhat crude. We conclude that Holl’s decision to describe this species and Mayr’s placement in Pheidole may have been hasty. The specimen studied by Schweigger is presumably lost, which precludes its proper placement using current genus concepts in Formicidae (Mayr 1868; Antweb 2019). Dlussky (2008) suggested treating †Formica cordata as Formicidae incertae sedis, and we concur that there is no strong reason to assume it belongs to Pheidole, though it is certainly a myrmicine ant. Thus, we consider †P. cordata as incertae sedis in Myrmicinae.
- Casadei-Ferreira, A., Chaul, J.C.M., Feitosa, R.M. 2019. A new species of Pheidole (Formicidae, Myrmicinae) from Dominican amber with a review of the fossil records for the genus. ZooKeys 866: 117–125 (DOI 10.3897/zookeys.866.35756).
- Holl, F. 1829. Handbuch der Petrefactenkunde. Bd. 2 [part]. Dresden: P. O. Hilschersche Buchhandlung, pp. 117-232. (page 140, soldier described)
- Mayr, G. 1868c. Die Ameisen des baltischen Bernsteins. Beitr. Naturkd. Preuss. 1: 1-102 (page 17, Combination in Pheidole)
- Schweigger, A.F. 1819. Beobachtungen auf naturhistorischen Reisen. Anatomisch-physiologische Untersuchungen über Corallen; nebst einem Anhange, Bemerkungen über den Bernstein enthaltend. Berlin: Reimer, 127 pp. (page 119, see also)