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Psyche 
[December 
roponera species except H. relicta (Wheeler). The latter could stand 
close to the Rhytidoponera ancestry. 
Aulacopone resembles Heteroponera in all fundamental structural 
details referred to in Brown’s discussion of features diagnosing or 
characterising ectatommine genera, except those related to cranial 
and petiolar structure, and other minor features, as detailed below. 
In discussing likely relationships among the ectatommine genera 
Brown considered Acanthoponera to be “the genus surviving with the 
greatest number of primitive characters”. Heteroponera was consid¬ 
ered “a rather conservative stock” that “can be derived directly from 
Acanthoponera ”, and Rhytidoponera was represented as a genus 
“very closely related to Heteroponera ” which “may have originated in 
the Australian region from some Heteroponera- like stock”. Accord¬ 
ing to Brown these genera stand apart as a lineage separate from that 
of the exclusively neotropical genera Ectatomma Fr. Smith and 
Paraponera Fr. Smith. Gnamptogenvs, while difficult to relate pre¬ 
cisely to other genera, “seems closer to the Acanthoponera / Hetero¬ 
ponera line than to Ectatomma". All the above genera are essentially 
epigaeic, in contrast to the two further ectatommine genera, Procera- 
tium Roger and Discothyrea Roger, which are cryptobiotic and 
“seem, on the basis of adult characters, to be closest to Heteropon¬ 
era ”, while “the Baltic Amber species Bradoponera meieri (Mayr) 
looks like a reasonable step in this line”. 
Workers of Proceratium and Discothyrea are notable for their 
possession of cryptobiotic attributes, including medium to small size, 
with relatively small eyes, reduced sculpture and pilosity, and depig- 
mented coloration. In particular the mesosomal structure is stream¬ 
lined, through ankylosis of its component sclerites, and the fronto- 
clypeal structure is highly modified. The antennal sockets are 
exposed in full-face view, through elevation of the lobes of the frontal 
carinae, and they have migrated anteromedially, carrying the clypeus 
and frontal area forwards to form a shelf-like process over the 
mandibles. This is especially prominent in Discothyrea, which usu¬ 
ally has an erect vertical plate separating the antennal sockets, a 
structure which in some species is “T” shaped in transverse section 
and extends back along the head to enclose an antennal scrobe on 
each side, usually accompanied by a weak parallel longitudinal con¬ 
cavity of the frons. Both Proceratium and Discothyrea have their 
tubulate abdominal segment IV reflexed downwards or forwards 
under the body, a characteristic shared with various Heteroponera 
