A new enigmatic ant genus from late Eocene Danish Amber and its evolutionary and zoogeographic significance

Gennady Dlussky

doi:10.4202/app.2012.0028

Abstract

Usomyrma mirabilis gen. et sp. nov., belonging to the tribe Leptomyrmecini of the subfamily Dolichoderinae, are described based on two males from the late Eocene Danish Amber. Usomyrma differs from Leptomyrmex by a set of plesiomorphic and autapomorphic features. Distinctly plesiomorphic characters include the fore wing venation, i.e., the presence of the well developed pterostigma, the wide closed cell 3r and the big central closed cell that formed by the fusion of the cells (1+2r)+mcu, and the structure of mandibles, which are elongate-triangular, with a well developed masticatory margin that, unlike Leptomyrmex, possesses a set of well developed, relatively long and sharp teeth. The most distinctive autapomorphy of Usomyrma is the structure of the antennae: although it remains 13-segmented, its second funicular segment is extremely elongate, much longer than any other segment, including the apical one. The generic composition of the tribe Leptomyrmecini is partly reassessed compared to the previously p...

Highlights

We propose to establish a new informal Leptomyrmex genus-group within tribe Leptomyrmecini, including in it the extant genus Leptomyrmex, two fossil (Usomyrma gen. nov., Leptomyrmula) and a “Leptomyrmex ” male from the Dominican Amber that probably represents a third extinct genus
We suggest that fore wing venation of Usomyrma is ancestral to other genera of this group
The evolutionary step was the complete reduction of the closed central cell in Leptomyrmula, while conserving the pterostigma and a wide closed cell 3r

Summary

Introduction

Nov., belonging to the tribe Leptomyrmecini of the subfamily Dolichoderinae, are described based on two males from the late Eocene Danish Amber. Usomyrma differs from Leptomyrmex by a set of plesiomorphic and autapomorphic features. Plesiomorphic characters include the fore wing venation, i.e., the presence of the well developed pterostigma, the wide closed cell 3r and the big central closed cell that formed by the fusion of the cells (1+2r)+mcu, and the structure of mandibles, which are elongate-triangular, with a well developed masticatory margin that, unlike Leptomyrmex, possesses a set of well developed, relatively long and sharp teeth.

Results

Conclusion