Aquilomyrmex huangi, Perrichot & Wang & Barden, 2020

Perrichot, Vincent, Wang, Bo & Barden, Phillip, 2020, New remarkable hell ants (Formicidae: Haidomyrmecinae stat. nov.) from mid-Cretaceous amber of northern Myanmar, Cretaceous Research 109, pp. 1-18 : 16-17

Key to genera and species of Haidomyrmecinae

1. Clypeus posteriorly with a slightly elevated setose lobe positioned just ventrad or between antennal insertion ……………………………………………………………… .. ……… ... 2

Clypeus posteriorly projecting forward into a cephalic horn arising ventrad, between, or dorsad antennal insertion ……………………………………………………………… .. ……… ... 5

2. Antenna compact, with flagellomeres short (<2 as long as broad); first flagellomere as long as or longer than second one ………………………………………………………………………… 3

Antenna elongate, with flagellomeres long (>2 as long as broad); first flagellomere shorter than second one ………… ……………………………………………… Haidomyrmex species: 4

3. All flagellomeres nearly of same length; clypeal setose pad positioned anterior to antennal insertion; ocelli present; two metatibial spurs ………………………………………………………… ………………… Haidomyrmodes mammuthus Perrichot et al., 2008 .

Flagellomere I longest of basal four flagellar articles; clypeal setose pad positioned slightly posterior to antennal insertion; ocelli absent; one metatibial spur ……………………… … .. … .. …… Haidoterminus cippus McKellar, Glasier & Engel, 2013 .

4. Flagellomere II longest of basal three flagellar articles; frontal triangle moderately elevated; vertex, ventral margin of mandibles, and antennomeres densely setose; mandibles with medioventral blade bearing at least one large apical tooth, with tip of apical portion tapered to acute point, smooth; ocelli reduced to pit-like traces; subpetiolar process present ……………………………. … Haidomyrmex cerberus Dlussky,1996

Flagellomere II longest; frontal triangle strongly elevated; vertex, ventral margin of mandibles, and antennomeres mostly glabrous; mandibles with medioventral blades asymmetrical, left one bearing three small teeth, right one bearing two larger teeth; tip of apical portion tapered to sharp point, smooth; ocelli and subpetiolar process absent ………………………………… ……………… Haidomyrmex scimitarus Barden & Grimaldi, 2012

Apical flagellomere longest; frontal triangle feebly elevated; vertex, ventral margin of mandibles, and antennomeres mostly glabrous; mandibles with medioventral blade bearing a single apical tooth, with tip of apical portion tapered to blunt point and minutely serrate; ocelli absent; subpetiolar process a minute tooth ……………………………………………………………………. …………………. Haidomyrmex zigrasi .. Barden & Grimaldi, 2012.

5. Posterior clypeal projection not furrowed ventrally (¼ without lateral ridges), forming a pointed or paddle-shaped horn; long, paired trigger setae present, arising from base of clypeal process or ventral surface of apical setose pad; peg-like denticles absent or present only on ventral setose pad; labrum not obviously exposed ……………………………………………………………. … 6

Posterior clypeal projection distinctly furrowed ventrally, with lateral ridges originating above mandible insertions, and converging posteriorly to form the lateral margins of a horn; paired trigger setae absent; peg-like denticles present along lateral clypeal ridges, or on labrum, or both; labrum exposed ventrally of horn …………………………………………………… 9

6. Clypeal horn a small triangulate cuticular elevation; one pair of trigger setae positioned at base of horn; compound eyes small (OI 24); ocelli absent; flagellomeres IIeX compact, barely longer than wide ……………………………………………………………… ……………………… Protoceratomyrmex revelatus gen. et. sp. nov.

Clypeal horn paddle-shaped, comprising basal stalk and apical setose pad; compound eyes small to large (OI 26e39); ocelli present; flagellomeres IIeX elongate, distinctly longer than wide ……………………………………………………………… .... ……… 7

7. Clypeal horn and curved apical portion of mandibles extremely long, reaching high above vertex (HoI 140; MDI 130); peg-like denticles present on ventral setose pad; 2 pairs of trigger setae positioned at base of horn's stalk; frontal triangle fused with horn, not distinguishable; gastral constriction between AIII and AIV at most faintly impressed ………………………………………………………………………… ... ……… Ceratomyrmex ellenbergeri Perrichot, Wang & Engel, 2016

Clypeal horn and curved apical portion of mandibles distinctly shorter, not reaching above vertex (MDI 70); peg-like denticles absent; 1 pair of trigger setae positioned on ventral surface of apical setose pad; frontal triangle connecting with horn by cleared cuticular membrane; gastral constriction between AIII and AIV deeply impressed ………………………………………… ……………………………………………. Linguamyrmex species: 8

8 Clypeal horn reduced (HoI 25e35), with stalk almost indistinct and apical setose pad hexagonal, as broad as (worker) or smaller than (gyne) compound eye's length (EL); mandibles with medioventral blade bearing two teeth and, in worker, surpassing midlength of apical curved portion; compound eyes small in worker (OI 25); propodeum higher than long … .. ………………. …… Linguamyrmex brevicornis gen. et. sp. nov.

Clypeal horn conspicuous (HoI 56), with stalk short, not surpassing frontal triangle in dorsal view, and apical setose pad circular, broader than EL in worker; mandibles with medioventral blade smooth and not reaching to midlength of apical curved portion; compound eyes large in worker (OI 39); propodeum longer than high ……………………………… …………………. … Linguamyrmex vladi Barden & Grimaldi, 2017 .

Clypeal horn enormous (HoI 95e105), with apical setose pad circular, nearly as broad as head in dorsal view, and stalk about as long as pad; mandibles with medioventral blade smooth and, in worker, not reaching to midlength of apical curved portion; compound eyes large in worker (OI 44); propodeum longer than high …………………………………………………………………… ………………… .. Linguamyrmex rhinocerus Miao & Wang, 2019 .

9 Body and legs robust; mandibles scythe-shaped, with medioventral triangular blade present; in frontal view, the outline of apical portion of mandibles aligned with clypeal lateral ridges; clypeal horn gradually tapering to rounded tip; genae elongate, the mandibles inserted far from compound eyes …………………………………………………………………… .. … 10

Body and legs gracile; mandibles sickle-shaped, with medioventral triangular blade absent; clypeal horn and labrum protruding horizontally, their tip with a deep median notch; apical lateral margins of horn bilobed; genae strongly reduced, the mandibles inserted close to compound eyes ……………………. ………. Aquilomyrmex huangi gen. et. sp. nov.

10 Mandibles with apical curved portion much longer than basal portion and entirely serrate along dorsal margin; with medioventral blade an isosceles tooth not projecting beyond mandibular elbow (labrum and clypeal surface below horn entirely exposed when mandibles closed); ocelli large, antennomeres and compound eyes distinctly elongate …………………………… Dhagnathos autokrator gen. et. sp. nov.

Mandibles with apical curved portion not distinctly longer than basal portion; with medioventral blade a large triangle gradually tapering to tip of apical portion (labrum and clypeal surface below horn entirely concealed when mandibles closed); dorsal margin of mandibles serrate along distal half of medioventral projection, bidentate apically; ocelli, antennomeres, and compound eyes more reduced ………… ……………………………… …………………………………… Chonidris insolita gen. et. sp. nov.