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Electromyrmex wheeleri
| †Electromyrmex wheeleri Temporal range: Bartonian, Middle to Late Eocene Baltic amber, Baltic Sea region | |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Hymenoptera |
| Family: | Formicidae |
| Subfamily: | Myrmicinae |
| Genus: | Electromyrmex |
| Species: | †E. wheeleri |
| Binomial name | |
| †Electromyrmex wheeleri Radchenko & Dlussky, 2018
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While revising Late Eocene European ambers we found two males that correspond to the main diagnostic features of Electromyrmex. However, the body length of the holotype worker of E. klebsi is about 5.5 mm, whereas body lengths of the recently found males are only 2.5–2.9 mm. We do not know any example among both extinct and extant ant genera when males are nearly twice smaller than the conspecific workers. This fact leads us to describe these males as a new species. (Radchenko & Dlussky 2018)
Identification
Radchenko & Dlussky (2018) - The morphological features of the males of E. wheeleri sheds little light on the systematic position of this genus. Thus, they share several characters with some modern Myrmicinae genera resembling Aphaenogaster, Messor and Pheidole by the forewing venation, but differing from the first two genera by the presence of Mayrian furrows, and from the latter by the antennal structure. Additionally, males of E. wheeleri have a set of specialized characters, e. g., subcylindrical petiole, mandible with an only single apical tooth, quite peculiar shape of mesosoma, etc., so taxonomic position of Electromyrmex remains unresolved.
Distribution
This taxon was described from Baltic amber (Bartonian, Middle to Late Eocene) and Bitterfeld amber (Bartonian, Middle to Late Eocene).
Castes
Male
Nomenclature
The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.
- †wheeleri. †Electromyrmex wheeleri Radchenko & Dlussky, 2018: 363, figs. 1-9 (m.) BALTIC AMBER (Eocene).
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
Description
Male
Holotype: HL 0.53, SL 0.26, OL 0.22, PL 0.33, PH 0.078, PPL 0.20, PPH 0.14, ML 1.07, MH 0.65, HTL 0.65, total length ca. 2.9. Ratios: SL/HL 0.49, OL/HL 0.42, PL / PH 4.17, PL /HL 0.61, PPL/PPH 1.36, PPL/HL 0.37, ML / MH 1.64. Paratype: HL 0.44 SL 0.20, OL 0.18, PL 0.26, PH 0.077, PPL 0.14, PPH 0.10, ML 0.90, MH 0.50, HTL 0.50, total length ca. 2.5. Ratios: SL/HL 0.46, OL/HL 0.41, PL / PH 3.38, PL /HL 0.59, PPL/PPH 1.40, PPL/HL 0.32, ML / MH 1.80.
Total length: ca. 2.5–2.9 mm. Despite width of head is not properly measurable, head seems distinctly elongate, much longer than broad. Occipital margin straight, sides of head very feebly convex, occipital corners moderately rounded. Clypeus convex (seen in profile), its anterior margin narrowly rounded, but not prominent and not notched medially. Antennal sockets quite deep. Eyes rather big, their maximal diameter ca. 2.5 times smaller than length of head. Ocelli well developed, though not too big. Antennae 13-segmented, with 4-segmented club, scape relatively short, subequal to total length of 1st to 4th funicular segments. Mandibles not very long, elongate-triangular, with distinct masticatory margin, which is with only single sharp apical tooth. Palp formula seems 5, 3 (these characters are not proper visible, palp formula may be less, but deFInitely not more than 5, 3).
Scutum relatively short and high, strongly convex, Mayrian furrows well developed. Propodeum very low and quite long, lays much lower than dorsal levels of scutum and scutellum (shape of mesosoma similar to that of males of several Aphaenogaster species), its dorsal and posterior surfaces subequal in length, almost straight, meet at an rounded angle, without any denticles or tubercles (seen in profile). Propodeal lobes widely rounded.
Petiole remarkable, very long and low, without node, subcylindrical, slightly curved dorsoventrally. Postpetiole small, higher tan petiole, subglobular.
Legs long and slender. Mid and hind tibiae without spurs, pretarsal claws simple.
Head, mesosoma and waist FInely though densely punctated, mesopleuron and sides of propodeum additionally with FIne longitudinal striation. Gaster smooth and shiny.
Head, mesosoma and waist with dense, silverish decumbent pubescence. Head (including its ventral surface), scutum and propodeal dorsum with sparse long suberect hairs, gaster with more abundant similar hairs. Scape without hairs, femora and tibiae with non-abundant, FIne, fairly short semierect hairs, tarsi with short bristles.
Forewing with closed cells 1r+2r, rm and mcu, cell 3r open; cell 1r+2r quite big, ca. twice longer than width, cell rm pedicellate.
Type Material
- Holotype, male, Baltic Amber (Eocene), GPIH number 4937, coll. Gröhn No. 6737, Geologisch-Paläontologisches Institut des Universität Hamburg.
- Paratype, 1 male, Bitterfeld Amber (Eocene), MNKB No. 10/216, Museum für Naturkunde Berlin, Germany (MNKB) (the former Zoological Museum of the Humboldt University).
Etymology
The species name is dedicated to W. M. Wheeler, famous American myrmecologist, who established the genus Electromyrmex.