Eotemnothorax gracilis

†Eotemnothorax gracilis; Temporal range: Priabonian, Late Eocene K Pa Eo Ol Mi Pl Baltic amber, Baltic Sea region
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Crematogastrini
Genus:	Eotemnothorax
Species:	†E. gracilis
Binomial name
	†Eotemnothorax gracilis; (Mayr, 1868)

Mayr (1868) described Leptothorax gracilis based on one worker and two males (the latter were preserved in the same piece of amber) from the collection of Königliche Bernsteinsammlung des Geologischen Instituts of Königsberg (“In der phys.-ökon. Ges.” according to Mayr 1868) (Baltic amber). Wheeler (1915) examined all of Mayr’s syntypes, and additional 28 workers and two males. He noted that the syntype worker “is badly decomposed and has apparently deteriorated since it was described by Mayr” (loc. cit., p. 63). Wheeler (1915) also noted, among other features, one important character of this species: “The petiole is as long as high in profile; its node angular, with subequal anterior and posterior slopes, both slightly concave” (loc. cit., p. 64). Syntype specimens of this species are lost, but there are two workers in the GZG collection, examined by Wheeler and identified as L. gracilis. However, one of them, with accession number GZG.BST.04661 (= K 843 according to Wheeler), has a widely rounded dorsum of the petiolar node, which differs well from that of E. gracilis, and I assigned this specimen to the Eotemnothorax balticus (Radchencko, 2024).

Photo Gallery

Radchenko (2024), Figure 1. Photographs of workers of Eotemnothorax gracilis, NEOTYPE: (A) body, lateral view; (B) body, dorso-lateral view); Eotemnothorax petiolatus, NEOTYPE: (C) body, lateral view; (D) body, anterior view); Eotemnothorax glaesarius, MKHC F-414: (E) body, dorso-lateral view; (F) waist and propodeum, dorso-lateral view.

Identification

Radchencko (2024) - By the mostly punctated mesosoma and waist E. gracilis resembles Eotemnothorax hystriculus, Eotemnothorax balticus and Eotemnothorax punctatus. It differs from the first two species by the cuneiform petiolar node (vs. node with rounded dorsum), and from the latter it differs by the presence of the distinct propodeal spines instead of the only short triangular denticles (ESL/HL > 0.20 vs. < 0.15, respectively).

Keys including this Species

Key to Eotemnothorax species

Distribution

This taxon was described from Baltic amber, Baltic Sea region, Europe (Priabonian, Late Eocene) and is also known from Bitterfeld amber, Baltic Sea region, Europe (Priabonian, Late Eocene) and Rovno amber, Baltic Sea region, Europe (Priabonian, Late Eocene) (Perkovsky, 2016).

Castes

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

†gracilis. †Leptothorax gracilis Mayr, 1868c: 89, pl. 5, figs. 89-92 (w.m.) BALTIC AMBER (Eocene).
- Combination in Temnothorax: Bolton, 2003: 271.
- Combination in Eotemnothorax: Radchenko, 2024: 721.

Type Material

Neotype worker (designated by Radchenko, 2024), complete specimen, Baltic amber, 4944 (CCGG 6814) (LIB).

Non-type material (Rachenko, 2024): worker, Baltic amber, 6761 (CCGG); 2 workers, Baltic amber, 6835 (CCGG); worker, Baltic amber, 9459 (JDC); worker, Rovno amber, K-2246 (SIZK); gyne, Rovno amber, K-3548 (SIZK); worker, Rovno amber, F-082 (MKHC); 2 workers, Rovno amber, F-250 (MKHC); worker, Rovno amber, F-425 (MKHC); worker, Rovno amber, F-504 (MKHC) (with 1 Trichoptera in same piece of amber); gyne, Bitterfeld amber, 12/201 (MNB); queen, Bitterfeld amber, 27.066 (GZG.BST) (collection of M. Kutscher).

Description

References

Aguayo, C. G. 1932. Notes on West Indian ants. Bull. Brooklyn Entomol. Soc. 27: 215-227 (page 223, worker described)
Baroni Urbani, C. 1978b. Materiali per una revisione dei Leptothorax neotropicali appartenenti al sottogenere Macromischa Roger, n. comb. (Hymenoptera: Formicidae). Entomol. Basil. 3: 395-618 (page 420, Replacement name: anemicus)
Bolton, B. 2003. Synopsis and Classification of Formicidae. Mem. Am. Entomol. Inst. 71: 370pp (page 271, Combination in Temnothorax)
Mayr, G. 1868c. Die Ameisen des baltischen Bernsteins. Beitr. Naturkd. Preuss. 1: 1-102 (page 89, p. 5, figs. 89-92 worker, male described)
Perkovsky, E.E. 2016. Tropical and Holoarctic ants in late Eocene ambers. Vestnik zoologii 50(2): 111–122 (doi:10.1515/vzoo-2016-0014).
Radchenko, A. 2024. Eotemnothorax gen. nov. (Hymenoptera: Formicidae) – A new ant genus from Late Eocene European ambers. Annales Zoologici 74(4), 717-752 (doi:10.3161/00034541anz2024.74.4.015).
Radchenko, A.G., Perkovsky, E.E., Vasilenko, D.V. 2021. Formica species (Hymenoptera, Formicidae, Formicinae) in late Eocene Rovno amber. Journal of Hymenoptera Research 82, 237–251 (doi:10.3897/jhr.82.64599).