The largest known ant species on earth comes from Germany – at least it was found here in 2003 in the Hessian pit Messel as a fossil: The queens of the Titanomyrma gigantea became more than six centimeters long and reached wingspans of about 15 Centimeters. A similarly large relationship was discovered by paleontologists in Wyoming in 2011, raising questions such as ancestors before 50 millions of years had managed to become native on both sides of the Atlantic. The way from Europa – here the origin is suspected – could only take place over Arctic land bridges, where it should actually be too cold for the large insects.
Bruce Archibald of Simon Fraser University in Burnaby and his colleagues describe in»The Canadian Entomologist»another fossil of a Titanomyrma ant from British Columbia (B.C.) , which puzzles scientists even more.»This ant and the new fossil from British Columbia are similar in age to other fossils that have long been known in Germany and England,» says Archibald. «This raises the question of how these ancient insects could have traveled between continents to appear on both sides of the Atlantic at almost the same time.» What’s more, while Europe and Wyoming were warm enough for large ants during the Eocene, this was not true for the highlands further north in Canada.
Like today’s ants, the fossil giant relationship was very likely ectothermic: it needed thermal energy from the environment to survive. In cold climates, this means more body surface area compared to body volume. Therefore, tropical ants are usually significantly larger than their relatives at higher latitudes. The Canadian Titanomyrma could test this connection if it actually turns out to be a giant.But the petrification process is not given to the insect. The geological pressure has deformed the six-legged friend, so its true size cannot really be determined. He may have been gigantic like some of the largest Titanomyrma queens. However, it could possibly be up to two-thirds smaller than the specimen from Wyoming.
«If it was a smaller species, did it adapt to this region with a cooler climate by shrinking?Then huge species could not exist here, as we predicted in 2011,» Archibald reflects. Or were they big and our idea of their climate tolerance and therefore the way they crossed the Arctic was wrong?»
Even if the Atlantic was 50 millions of years narrower than today, paleontologists assume that the ants had to use a land bridge. So far, they suspect that they succeeded in doing this during short periods in which the average temperatures were even higher than in the already warm Eocene. . They even warmed the Arctic so much that large insects could cross them.
However, if it turns out that Titanomyrma was indeed a giant, these ants would have had a greater cold tolerance than modern species. Their journey through the Arctic would then have been possible under other conditions.This could only be clarified by further fossil finds, the scientists write.
From a purely ecological point of view, the find is exciting anyway: the large ants also needed large amounts of food. Like today’s tropical driver ants, they probably roamed the rainforests of the Eocene in search of other insects and smaller vertebrates.
Source — https://www.spektrum.de/news/insekten-vogelgrosse-ameise-stellt-forscher-vor-raetsel/2118057