Pristomyrmex archaios

†Pristomyrmex archaios; Temporal range: Bartonian, Middle to Late Eocene K Pa Eo Ol Mi Pl Bitterfeld amber, Sachsen-Anhalt, Germany
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Crematogastrini
Genus:	Pristomyrmex
Species:	†P. archaios
Binomial name
	†Pristomyrmex archaios; Radchenko & Dlussky, 2018

This species is only known from the holotype and paratype males. Both are contained in a single piece of Bitterfeld amber.

Identification

Radchenko & Dlussky (2018) - Most characters of the male P. archaios undoubtedly are consistent with Pristomyrmex, but its forewing venation is somewhat different. Particularly, the forewing in extant species of this genus has only one closed cell, 1r+2r, while the cell mcu in P. archaios is also closed. As process of reduction of the wing venation in ants is well known evolutionary trend, we believe that the forewing venation in P. archaios is more primitive compared to modern species.

Distribution

This taxon was described from Bitterfeld amber, Baltic Sea region, Europe (Bartonian, Middle to Late Eocene).

Castes

Nomenclature

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

†archaios. †Pristomyrmex archaios Radchenko & Dlussky, 2018: 253, fig. 3 (m.) BITTERFELD AMBER.

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 0.59, HW 0.52, SL 0.16, OL 0.33, PL 0.37, PH 0.29, PPL 0.19, PPH 0.19, PPW 0.27, HTL 0.61, ScW 0.67, ScL 0.93; paratype: HW 0.51, SL 0.16, OL 0.32, ML 1.23, MH 0.88, ScW 0.67, ScL 0.91, HTL 0.64. Ratios: holotype: HL/HW 1.13, SL/HL 0.27, SL/HW 0.31, OL/HL 0.57, PL/PH 1.27, PL/HL 0.64, PPL/PPH 0.78, PPL/HL 0.32, ScL/ScW 1.40; paratype: SL/HW 0.32, ML/MH 1.39, ScL/ScW 1.36.

Total length: ca. 3.5 mm. Head slightly longer than width, gradually rounded above eyes. Eyes very big, their maximum diameter more than half of head length, genae very short; ocelli very big. Anterior clypeal margin straight, without notch or dents. Antennae 12-segmented, without club, scape short, somewhat shorter than second funicular segment; 2nd to 9th funicular segments subequal in length, terminal one the longest. Mandibles strongly reduced, vestigial, look like short triangles. Palp formula 5, 3.

Mesosoma relatively short and high, ca. 1.4 times longer than height, scutum convex, Mayrian furrows well developed, deep, Y-shaped; scutum not wide (seen from above). Propodeum rounded, without tubercles, its dorsal surface somewhat shorter than posterior one. Propodeal lobes widely rounded. Petiole with distinct peduncle, but not very long, its anterior surface somewhat concave, node narrowly rounded, subconical; postpetiole somewhat longer than height, with rounded dorsum. Forewing with closed cells 1r+2r and mcu, cell 3 r open.

Middle and hind tibiae with barbulate spur, pretarsal claws simple.

Whole body with fine superficial micropunctures, appears dull. Head, mesosoma and waist with both long and short suberect hairs, without decumbent pubescence. All antennal segments with very dense, short subdecumbent pubescence.

Type Material

Holotype and paratype in the same piece of amber, males, GZG.BST (Geowissenschaftlicher Zentrum der Ge org-August-Universitat Göttingen, Germany) No. 27.041, Bitterfeld amber, Late Eocene, Germany.

Etymology

The species is named after Greek word αρχαίος – ancient, to stress more primitive character of the forewing venation compare to modern species.

References