Zigrasimecia is an extinct genus of ants which existed in the Cretaceous period approximately 98 million years ago.

The first specimens were collected from Burmese amber in Kachin State, 100 kilometres (62 mi) west of Myitkyina town in Myanmar.

In 2013, palaeoentomologists Phillip Barden and David Grimaldi published a paper describing and naming Zigrasimecia tonsora.

Other features include large ocelli, short scapes, 12 antennomeres, small eyes, and a clypeal margin that has a row of peg-like denticles.

The highly movable head suggests that mobility was an important factor for them (probably for feeding behavior), and the rugose projections may have played a major role in nest excavation because the mandibles would have prevented such activity.

Zigrasimecia most likely interacted with the extinct ant genus Gerontoformica through conflict and probably shared some of their ecological niches.

The mandibles of these ants were probably used for mechanical interactions with food, and they may also have served as traps for potential arthropod prey such as mites and small flies.

At the time of description, the specimen was residing in the private collection of James Zigras and only available for study through the American Museum of Natural History.

The amber specimen was recovered from deposits in Kachin State, 100 kilometres (62 mi) west of Myitkyina town in Myanmar.

Burmese amber has been radiometrically dated using U-Pb isotopes, yielding an age of approximately 99 million years old, close to the Albian – Cenomanian boundary.

[2] Barden and Grimaldi's 2013 type description of the new genus and species was published in the online journal Zootaxa.

[2] In Barden and Grimaldi's article, the authors could not sufficiently identify the ant with enough confidence to place it in a subfamily.

[2][4] Although a recent published morphological study provided useful information on the mouthparts of basal ants,[5] placing Cretaceous taxa is still difficult.

[2][6] The morphology of Z. tonsora shows a variety of autapomorphies (derived traits) not seen in any other ant species, particularly the structure of the mandibles and mesosomal sculpturing.

[2][7] In 2014, palaeoentomologist Vincent Perrichot of the Université de Rennes studied a number of specimens recovered in amber from the Late Cretaceous, dating back to 98 million years.

For example, the antennae are geniculate and the scapes are rather short; the funiculus (segments between the antennal base and club) is filiform; there are no known propodeal lobes (a carina that delimits the propodeal scrobe laterally); two spurs are present on the mesotibia and metatibia (the middle and hind part of the tibia); and a preapical tooth is found on the claws and a sting is present.

Its placement within the tribe Sphecomyrmini is supported by the female mandibles bearing two teeth and the elongated third antennal segment.

[9][10] Based on the apomorphic characters, Zigrasimecia species may share a close relationship with other extinct ants such as Gerontoformica, particularly those that were in the former genus Sphecomyrmodes.

Although Z. tonsora is not present in the cladogram, the placement of Z. ferox gives insight to the placement of the genus:[11] In 2017 Zigrasimecia was placed into the separate tribe Zigrasimeciini, which was later upgraded to the distinct family Zigrasimeciinae in 2020, alongside the genera Boltonimecia and Protozigrasimecia also known from Cretaceous amber, due to their uncertain relationship to other Cretaceous stem-group ants.

The head is similar to those of queens of Z. tonsora, but they can be separated by the lack of ocelli and rugose patches found on the vertex.

The mesosoma is smooth and contains a single spine, fovea (a pit or depression in a structure) or carina (a keel-like elevation on the body-wall of an insect).

Like the queen, Z. ferox has a large, retractable stinger, in which the external part is enclosed by the gonostyli (sting sheaths).

The posterior corners are round and the base of the ants' mandibles are concealed by the large expansion of the gena (area below the compound eyes, the insect equivalent to human cheeks).

The trochantellus (proximal end of the femur) is found on all legs, and the forelegs have patches of dense and elongated setae.

The antenna is 1.42 millimetres (0.056 in) long, and has a total of 12 antennomeres, with the flagellum (an antennal segment) composed of ten flagellomeres.

The mesopleuron is separated from the mesosoma by complete sulci, and when viewed dorsally, it bears a series of C-shaped grooves and foveae.

[2] Also, Zigrasimecia and Gerontoformica ants coexisted with each other; this is evident as a recovered piece of amber showed both genera trapped inside.

[8] It is not known what the function of the oral setae in extant species is, other than the long sensory hairs seen in some genera such as Anochetus and Odontomachus.

The setae may have allowed the manipulation of liquid food, and the unification of the mandibles with other body parts such as the clypeus and labral indicates that they served as a trap for potential arthropod prey, particularly mites and small flies.

The unusual mouthparts of Zigrasimecia are consistent with other extinct species found in Burmese, French, New Jersey and Canadian deposits, which also show morphologies not seen in extant ants.