Macabeemyrma is an extinct genus of bulldog ants in the subfamily Myrmeciinae containing the single species Macabeemyrma ovata, described in 2006 from Ypresian stage (Early Eocene) deposits of British Columbia, Canada. Only a single specimen is known; a holotype queen found preserved as a compression fossil. The specimen had no wings and small portions of its legs and eyes were faintly preserved. It was a large ant, reaching 25 millimetres (0.98 in) in length. This ants' behaviour would have been similar to that of extant Myrmeciinae ants, such as foraging singly in search for arthropod prey and nesting in soil or in trees. Macabeemyrma shows similarities to extinct ants in the genus Ypresiomyrma, and to the living Nothomyrmecia macrops, but has not been conclusively assigned to any tribe, instead generally regarded as incertae sedis within Myrmeciinae. However, the sole specimen lacks definitive traits, and its classification in Myrmeciinae, and even its identity as an ant, has been challenged.
Macabeemyrma ovata is known only from a single fossil specimen: a mostly complete adult queen, preserved as a compression fossil in fine-grained shale.[2] The shale is from fossiliferous outcrops at the McAbee Fossil Beds, part of an unnamed bed in the Kamloops group Tranquille Formation which outcrops east of Cache Creek in British Columbia, Canada.[3] The holotype specimen was collected by an unknown person and donated to Thompson Rivers University in 2002.[4][5] The specimen was described by Bruce Archibald, Stefan Cover and Corrie Moreau of Harvard University's Museum of Comparative Zoology, with their 2006 type description of the genus and species. The generic name Macabeemyrma is a toponym of the type locality at McAbee[a] combined with the Greek myrmex, meaning "ant". The specific epithet ovata, from the Latin "ovatus" meaning "egg shaped", refers to the shape of the head capsule.[6]
Archibald and colleagues originally classified Macabeemyrma as incertae sedis (Latin for "of uncertain placement") within the ant subfamily Myrmeciinae, as it could not be confidently placed into any ant tribe. However, in a 2008 paper, Cesare Baroni Urbani of the University of Basel, Switzerland, noted that the specimen shares some traits found in other ant subfamilies and some wasps, and lacks key diagnostic traits (synapomorphies) of the ant family, Formicidae, and thus argued Macabeemyrma could only be confidently classified as incertae sedis within the order Hymenoptera.[7][8] A subsequent report describing new fossil myrmecines accepted the classification of Archibald and colleagues without comment on the views of Baroni Urbani.[3]
The following cladograms generated by Archibald and colleagues show two possible phylogenetic positions of Macabeemyrma among some ants of the subfamily Myrmeciinae; the cladogram on the right included three additional extinct genera compared to that on the left.[9] They suggest that Macabeemyrma ovata and other extinct ants such as Avitomyrmex and Ypresiomyrma may be closely related to the living Nothomyrmecia macrops.[10]