Rediscovery of the Baltic amber ant genus Prionomyrmex (Hymenoptera, Formicidae) and its taxonomic consequences

Two specimens of the Baltic amber monotypic ant genus Prionomyrmex, known only on a few specimens supposed to have been destroyed during the Second World War, are described as a new species, P. janzeni, P. janzeni shows remarkable similarities with the Recent Australian genus Nothomyrmecia. A parsimony analysis of the relationships between the three most closely related genera, i.e. Myrmecia (Recent Australian), Nothomyrmecia (Recent Australian), and Prionomyrmex (Baltic Eocene) based on 34 morphological characters, suggests the following phylogeny: (Myrmecia, (Nothomyrmecia, Prionomyrmex)). In this reconstruction, however, Nothomyrmecia is characterised by only two, doubtful, apomorphies and Prionomyrmex is paraphyletic to it. As a consequence of this, the following nomenclature changes are proposed: 1. The genus Nothomyrmecia Clark, 1934 is a junior synonym of Prionomyrmex Mayr, 1868. 2. Prionomyrmex macrops (Clark) is a new combination (from Nothomyrmecia). 3. The subfamily Nothomyrmeciinae Clark, 1951 is a junior synonym of the tribe Prionomyrmeccini Wheeler , 1915. 4. The tribe Prionomyrmecini Wheeler, 1915 is raised to subfamilial status (Prionomyrmeccinae, new status). In this classification the Myrmeciinae result characterised by four apomorphies and the Prionomyrmecinae by three: one undoubted, the appearance of a lateral cylpeal carina, and two verified in the Recent species only and assumed by extrapolation from similarity in "Bauplan" to be present in the fossils as well, presence of a ventral stridulitrum and of a biaculeate subgenital plate. It is stressed by a hypothetical future demonstration of absence of the last two characters in the fossil species will not affect the classification proposed in this paper. This hypothetical discovery, in fact, would render again Prionomyrmex paraphylectic to Nothomyrmecia and hence its senior synonym.