This is an amazing dexiine with a very Estheria-type face – small antennae, plumose arista, very deep gena, very chin-less profile and a very stretched-out ‘top lip’ with a second, higher pair of vibrissae. The bend in the median vein is quite acute and the part of m after the bend is very concave. There is no petiole but the bend in m has a long appendix.
EDIT (4/10/2010): After keying in MCADv2 these come out to 2 genera. The upper photos are 2 specimens of a genus called Pyrrhodexia and the lower ones are a specimen of Acronacantha cf. nubilipennis (the only known species).
These photos represent 3 specimens: