Avitomyrmex
Avitomyrmex is an extinct genus of bulldog ants in the subfamily Myrmeciinae which contains three described species. The genus was described in 2006 from Ypresian stage (Early Eocene) deposits of British Columbia, Canada. Almost all the specimens collected are queens, with an exception of a single fossilised worker. These ants are large, and the eyes are also large and well developed; a sting is present in one species. The behaviour of these ants may have been similar to extant Myrmeciinae ants, such as foraging solitarily for arthropod prey and never leaving pheromone trails to food sources. Avitomyrmex has not been assigned to any tribe, instead generally being regarded as incertae sedis within Myrmeciinae. However, its identity as an ant has been challenged, although it is undoubtedly a hymenopteran insect.
Avitomyrmex is an extinct genus of ants with three described species.[2] Fossils of Avitomyrmex, along with other extinct Myrmeciinae ants were first studied and described by Bruce Archibald, Stefan Cover and Corrie Moreau of the Museum of Comparative Zoology in Cambridge, Massachusetts. They published their 2006 description of the genus and species in an Annals of the Entomological Society of America journal article.[3] The genus name is a combination of the Latin "avitus" meaning "ancient" or "grandfatherly" and the Greek myrmex, meaning "ant".[2]
Included with the genus description, the paper contained the description of Avitomyrmex mastax, Avitomyrmex systenus, and the type species Avitomyrmex elongatus.[4] These fossil species date back to the Middle Ypresian.[3]
Archibald and colleagues originally classified Avitomyrmex as incertae sedis (Latin for "of uncertain placement") within the ant subfamily Myrmeciinae, as the specimens are unable to be properly identified.[5] In 2008, however, Cesare Baroni Urbani of the University of Basel, Switzerland, noted that no specimen in this genus allows a proper examination of the apomorphy (key diagnostic traits) of the subfamilial or familial characters. While Baroni Urbani excludes Avitomyrmex from Myrmeciinae and classifies it as incertae sedis in Hymenoptera, the morphological characters and wings show the specimens are undoubtedly a hymenopteran insect.[6] A 2012 report by Russian palaeoentomologist Gennady M. Dlussky of the Moscow State University describing new myrmecines accepted the classification of Archibald and colleagues without mentioning the comments of Baroni Urbani.[7]
The following cladograms generated by Archibald and colleagues show two possible phylogenetic positions of Avitomyrmex among some ants of the subfamily Myrmeciinae; the cladogram on the right included three additional extinct genera compared to that on the left. It is suggested that Avitomyrmex may be closely related to other extinct Myrmeciinae ants such as Macabeemyrma and Ypresiomyrma, as well as the extant Nothomyrmecia macrops.[8]
There are several characters which separate Avitomyrmex from other ant genera. The most notable feature is the distinctly slender nature of the queens and workers morphology. This is shown clearly in the shape of the petiole connecting the thorax and the abdomen. While similar to the modern myrmeciine genus Nothomyrmecia of Southern Australia, the two genera are distinguishable by the structure of the petiole, with Avitomyrmex lacking the peduncle seen in Nothomyrmecia. The eyes are large and well developed, the mandibles are subtriangular but poorly preserved, and a sting is present on examined A. systenus fossils.[2] As for A. elongatus and A. mastax, it is unknown if the two ants have a sting, due to either poor preservation or the sting has not been preserved at all.[9][10]
