Haidomyrmex Dlussky

ENGEL, MICHAEL S. & GRIMALDI, DAVID A., 2005, Primitive New Ants in Cretaceous Amber from Myanmar, New Jersey, and Canada (Hymenoptera: Formicidae), American Museum Novitates 3485, pp. 1-24 : 11-13

Genus † Haidomyrmex Dlussky

† Haidomyrmex Dlussky, 1996: 84 . Type species: † Haidomyrmex cerberus Dlussky, 1996 , monobasic and original designation.

DIAGNOSIS: Clypeus a small, hemispheric lobe lying just below antennal bases, possessing brush of ca. 60 fine, stiff, whitish setae; setae are evenly arranged, those on ventral margin thickened at base but taper to a fine point apically. Compound eyes small, length ca. 0.23 length of head capsule; ocelli absent. Mandibles elongate, scimitar­shaped, without serrations or teeth. Propodeum rounded in profile. Petiole one­segmented, nodiform, with distinct constriction at articulation with remainder of metasoma. Known from the worker caste only.

COMMENTS: The head of † Haidomyrmex is enigmatic (fig. 7) and much of the detail is obscured below the clypeus and where the mandibles articulate. Indeed, it is likely that there has been significant distortion at the manibular bases resulting in the rather ‘‘deep’’ appearance they have relative to the clypeus.

The peculiar clypeal setae may have served a sensory function, perhaps as trigger hairs for the large mandibles, much the way gaffshaped mandibles of various myrmecines and ‘‘poneroids’’ function. In those living ants long, fine, stiff trigger setae lie on the inside surface of the mandibles and on the oral margin. † Haidomyrmex has no such setae, so perhaps the clypeal brush functioned analogously. How † Haidomyrmex might have fed itself is an enigma. It is possible that this worker is similar to the major workers of Eciton , which cannot feed themselves.

† Haidomyrmex cerberus Dlussky

Figures 7–8

† Haidomyrmex cerberus Dlussky, 1996: 85 .

HOLOTYPE: NHML In.20182, partial work­ er specimen in amber from Myanmar.

COMMENTS: We have tentatively followed past authors in placing † Haidomyrmex within †Sphecomyrminae (e.g., Bolton, 2003). However, it is important to note the significant similarities between this genus and † Brownimecia in New Jersey amber (vide infra). Both genera have large, dome­shaped heads, with relatively small compound eyes, lack ocelli, have large mandibles devoid of serrations or dentition, and an elongate anterior extension, or collar, of the pronotum.

TABLE 3 Leg Measurements (in mm) for † Sphecomyrma freyi (AMNH NJ­943)

SUBFAMILY † BROWNIMECIINAE BOLTON

Genus † Brownimecia Grimaldi, Agosti, and Carpenter

† Brownimecia Grimaldi, Agosti, and Carpenter, 1997: 20 . Type species: † Brownimecia clavata . Grimaldi, Agosti, and Carpenter, 1997, monobasic and original designation.

DIAGNOSIS: Antenna distinctly clubbed, apical funicular article twice the width of basal ones and pedicel. Ocelli absent. Mandibles long, thin, scimitar­shaped, strongly cruciate, without teeth or crenulations, but with oral surface bearing about 30 short, spiculelike setae. Metasoma with slight but definite constriction between second and third segment (also known as abdominal segments III and IV; gastral segments 1 and 2). Known from the worker caste only.

† Brownimecia clavata Grimaldi, Agosti, and Carpenter

† Brownimecia clavata Grimaldi, Agosti, and Carpenter, 1997: 20 .

MATERIAL: AMNH NJ­ 941, in amber from

New Jersey: Middlesex Co., Sayreville, White Oaks outcrop, collected by Steve Swolensky.

COMMENTS: A beautifully preserved specimen in clear yellow amber, 5 3 8 mm, which was embedded in epoxy and trimmed to 2 mm thickness. Like the holotype which was described in 1997, it is curled up and the sting is extruded. The piece also contains some wood fragments and a frass pellet. The length of head (including closed mandibles) 0.88 mm, greatest width of head 0.74 (between outer margins of eyes), length of eye 0.24 mm, length of trunk 0.94 mm, length of petiole 0.32 mm. The mandibles are tightly closed, so details are less visible than in the holotype. The front portion of the head, however, and especially the clypeus, are more visible. The clypeus has fine, parallel crenulations along and perpendicular to the dorsal margin of the clypeus. Most significantly, ocelli are definitively absent (rather than vestigial or minute). Three large ocelli are rare in ants, with scattered occurrence (e.g., Cerapachyinae [ Cylindromyrmex , Simopone ], Formicinae [Aphophomyrmex, Notostigma , Alloformica , Cataglyphis ], Myrmeciinae [ Myrmecia ]), otherwise the ocelli are repeatedly lost, reduced, or modified secondarily (as is true for † Brownimecia ). The large, well­developed ocelli of † Sphecomyrma are clearly a plesiomorphic feature and part of the formicid ground plan.

SUBFAMILY INCERTAE SEDIS

Figures

Fig. 7. Facial view of holotype worker of †Haidomyrmex cerberus Dlussky (NHML In.20182).

Fig. 8. Lateral view of mesosoma and petiole, as preserved, of holotype worker of †Haidomyrmex cerberus Dlussky (NHML In.20182).