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Diagnosis of worker. Monomorphic arboreal myrmicine ants. Mandibles with 5 sharply defined large triangular teeth, the mandibles almost entirely concealed by the clypeus when closed. Palp formula 5, 3, the palpomeres very long (apical maxillary palpomere equal in length to apical antennal segment). Clypeus very large, projecting forwards over the mandibles as a broad shelf. Median portion of clypeus raised, broad posteriorly and broadly inserted between the widely separated frontal lobes. Frontal lobes concealing antennal insertions, prolonged back by a pair of irregular frontal carinae which run past the inner margins of the eyes to the occipital margin. Frontal carinae forming dorsal margins of a weak scrobe which is bounded below by a ridge running from below the eye to the mandibular insertions. Eyes large, situated at extreme posterolateral corners of head, within the scrobal area as defined by the frontal carinae and ridge. Antennae 12 - segmented, without a strongly defined club, the flagellomeres increasing in size apically. Occipital margin bounded by a broad transverse lamella which projects into a series of dentiform processes; occiput behind the lamella broad and flat. Promesonotum swollen, large and convex, without sutures but with 4 pairs of roughly triangular teeth or prominences. Propodeum short and strongly bispinose. Metapleural lobes absent. Mesopleuron divided by a broad transverse suture and a broad suture separating meso- and metapleuron present. Petiole strongly bispinose, with a broad anterior peduncle which grades into the node. Gaster consisting almost entirely of the massively enlarged and strongly vaulted first tergite. The first sternite is visible as a narrow collar fringing the ventral portion of the forward-pointing orifice of the tergite; remaining gastral segments very small and telescoped inside. Sting strongly developed and projecting anteriorly below the pedicel segments.
In the original description of this remarkable ant I placed the genus tentatively in the tribe Meranoplini HNS . I am aware now that this move was incorrect and that Ankylomyrma HNS is not close to Meranoplus HNS or any other member of that now-disbanded tribe (for discussion see Bolton, 1981). The real relationships of Ankylomyrma HNS are an enigma for, although there are a number of characters implying alliance with genera such as Atopomyrmex HNS , Terataner HNS and their allies, such as low dental count, high palp formula, broad clypeus and structure of petiole, there are also objections to such a placement. Chief among these must be the position of the eyes, situated as they are at the extreme posterior corners of the sides of the head and within what is strictly the scrobal area. In Terataner HNS and allies the eyes are always positioned well forward of the occipital corners and below the scrobes when such are present. The incredible occipital fringe and unique gastral development of Ankylomyrma HNS are of? course very derived characters which, though they serve to isolate the genus, do nothing to indicate its relationships. The only known species is as follows.