As so many of you guessed, the Getty Taxonomy Fail was not an Atta but an Acromyrmex.
JasonC- who is rapidly emerging as the Monday Night Superstar- was the first to pick it. Eight points for getting the answer right and most of the way there with a supporting explanation. Two more points to NKanakis for a more precise discussion of the difference: Atta has two pairs of spines on the promesonotum, while Acromyrmex bears three pairs.
Back when I lived in Paraguay, I learned the local Guaraní language distinguishes between the two genera. Ysaú for Atta, and Akéké for Acromyrmex. We don’t make such a distinction in English, where both lineages are called leafcutter ants.