Boltonimecia

History and classification

Boltonimecia is known from a single adult fossil, the holotype, specimen number "CAS 330" entombed in an 8 mm × 3 mm × 2 mm (0.315 in × 0.118 in × 0.079 in) amber chunk. At the time of the genus description, the specimen was residing in the Canadian National Collection of Insects, Arachnids and Nematodes, in Ottawa, Canada. The described specimen is of a worker caste adult which has been preserved as an inclusion in a transparent orange chunk of Canadian amber. The amber specimen was recovered in situ from the Taber coal zone near the top of Foremost Formation around Grassy Lake which is near Medicine Hat, Alberta, Canada. Canadian amber has been dated to an age of approximately 79–78 million years old, placing it in the Campanian of the Late Cretaceous.

Two workers were first studied by paleoentomologist E. O. Wilson in 1985, a holotype and less complete paratype, both of which were held in the collections of the Biosystematics Research Institute in Ottawa. In the type description they were placed by Wilson as a species of Sphecomyrma, Sphecomyrma canadensis, with the species name a reference to the country of discovery. The similarity of visible traits between S. freyi and "S." canadensis was mentioned by Wilson in the description, but little descriptive information distinguishing the two was provided.

It was noted in 1988 by Dlussky and Fedoseeva that the original description was based mostly on measurements alone and further that the holotype and paratype workers were likely not from the same ant genus. In 1996, Dlussky noted the antennae of "S." canadensis differed from S. freyi, having a longer first and fifth funicular segments, while in S. freyi it is the second segment which is longest.

An analysis and re-examination of the type workers was conducted by Leonid H. Borysenko of the Canadian National Collection of Insects, Arachnids and Nematodes and the results were published in a 2017 paper. While examining the holotype, Borysenko noted that most of the head along with parts of the antennae and mandibles were obscured by positioning in the amber. Sections of the specimen were re-polished and a number of new details became visible, allowing for the re-description of the extinct species into a new genus, Boltonimecia. The genus name was coined as a patronym in honor of the myrmecologist Barry Bolton. Borysenko placed Boltonimecia into a new tribe of Sphecomyrminae, Zigrasimeciini along with the sister genus Zigrasimecia. Examination of the paratype worker led Borysenko to conclude that the ant was too fragmented and no identifying characters were present, and thus not to be included as a paratype.