If you watch this video about a new technology for visualizing insect fossils hidden in opaque amber, pay special attention around 0:36-0:44. There's a brief 3D image of what is clearly a well-preserved sphecomyrmine ant. The clip is excerpted from a detailed demonstration here, showing the insect in all its glory (warning: 57MB!). It's among the most detailed glimpses of a Sphecomyrmine yet.
Why is this ant interesting? Sphecomyrminae is in many respects a classic piece of evidence for the wasp ancestry of ants. It is an extinct Cretaceous subfamily that shows a few characteristics of present-day ants (the constricted petiole, a wingless worker caste, and a metapleural gland) but it also retains a series of ancestral wasp characters (the antennae are not elbowed as in modern ants and the mandibles are small and two-toothed instead of broadly triangular). I could not imagine a fossil that better documents an important evolutionary transition.
Grimaldi, D. A., D. Agosti and J. M. Carpenter. 1997. New and rediscovered primitive ants (Hymenoptera: Formicidae) in Cretaceous amber from New Jersey, and their phylogenetic relationships. American Museum Novitates 3208: 1-43.
Engel, M. S. and D. A. Grimaldi. 2005. Primitive New Ants in Cretaceous Amber from Myanmar, New Jersey, and Canada (Hymenoptera: Formicidae) American Museum Novitates 3485: 1-23.
Schultz, T.R. 2000. In Search of Ant Ancestors. PNAS 97: 14028-14029.
Rats. I just zipped here to call this to your attention! Ah, well. Maybe next time. :)
"Sphecomyrminae is in many respects a classic piece of evidence for the wasp ancestry of ants."
Being hopelessly biased towards vertebrates, I did not know this! Interesting, I'll have to read about this.
Yep, it's got sphecomyrmecine antennae, alright. But, I'd like to get a better look at its abdominal apex. Almost looked like an acidopore in the fleeting view I saw in the video.