Sent in by William. At https://www.yahoo.com/news/fossil-fearsome-hell-ant-used-183903680.html … the fossil of a hell ant, belonging to the Cretaceous, is described as a fearsome beast. Captured in amber one can see the tusk like mandibles and horns used to hunt down prey. At the moment they are said to have only been active for 20 million years. They clearly disappeared at the K/T boundary event. Did they really only evolve just before that upheaval?
The study, in Current Biology, unveiled a fossil of a hell ant, in the act of embracing its unsuspecting victim, a cockroach. Instant fossilisation by tree resin. Presumably the ant and the cockroach were on the tree, or beneath it, when a splodge of resin fell down and squished them, preserving them in perfection. Previously, the hell ant has only been found in Cretaceous sediments, dated shortly prior to the boundary event.
Mind you, why it is called a 'hell' ant is not obvious. It seems to be doing nothing worse than other predatory creature, capturing prey to feast upon. I suppose it probably has something to do with its size – but it lived during the dinosaur era when a lot of other creatures were oversized as well. Dragon flies, for example. Either that or someone was simply averse to ants. They do have a tendency to crawl all over the place, even up the trouser leg given half a chance. They sometimes bite as well and the hell ants did have a bigger way of chomping.