99-Million-Year-Old Unicorn Ant Trapped Large Prey With Its Giant Horn

May 31, 2016 | Erica Tennenhouse

Ceratomyrmex ellenbergeri
Photo credit: Yang Dinghua. Artist's reconstruction of Ceratomyrmex ellenbergeri

Newly described Cretaceous killer had highly specialized head structures.

Fossils of a new ant species were discovered in 99-million-year-old chunks of amber recovered from Myanmar. The most striking feature of this ancient ant is a unicorn-like horn that protrudes from the top if its head — a structure of this kind has never been seen among the estimated 14,000 extinct and living ant species.

Reporting in the journal Current Biologythe researchers describe bristles covering the underside of the horn, and on the ant’s two large mandibles — the appendages near its mouth used in capturing prey.

Ceratomyrmex ellenbergeri in amber

Photo of Ceratomyrmex ellenbergeri. Black arrow indicates mandible and white arrow indicates horn. Photo credit: V. Perrichot

These types of bristles usually serve a sensory function in insects. For example, trap-jaw ants have two powerful mandibles that are normally locked open in a wide gape. When trigger hairs on the insides of the mandibles are touched, the jaw snaps shut on prey.

The authors write that the horn and trigger hairs of this newly described species seem to have similarly operated “as a sensory complex to judge the distance of a target before eliciting closure of the oversized mandibles, presumably to subdue, puncture, and crush prey or opponents, and alternatively for contact with nestmates without eliciting a strike.”

With the help of its horn, the ant appears to have been highly specialized in trapping large prey.

The researchers were surprised to find that such an exaggerated specialized structure occurred as early as the Cretaceous — a period in which the first ant groups were just beginning to diversify.

After this horned ant went extinct, it would be millions of years before similar specialized prey-trapping body parts would arise again in the lineage leading up to modern-day trap-jaw ants.

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