Ancient whale fossilized with its last meal

A. Gennari

Ancient whale fossilized with its last meal

Beaked whales, which often have dolphinlike snouts rather than blunt muzzles, typically dive hundreds of meters or more to chase squid, fish, and other prey. But at least one ancestral species in this group of toothed whales, also known as ziphiids, was cruising near-surface waters for its meals, new evidence from newly described fossils suggest. Those remains—the first of any toothed whale to also include fossils of its presumed prey, researchers say—were unearthed along the southwestern coast of Peru last year. The rocks that entombed the partial remains of the whale (Messapicetus gregarius, depicted in an artist’s reconstruction, above) accumulated as sea-floor sediments between 8.9 million and 9.9 million years ago, other fossils in the rocks suggest. The whale’s remains would be largely unremarkable if not for the large number of sardinelike fish preserved inside its chest cavity and around its head. Because scales of the fish show few signs of being exposed to stomach acid, the fish must have been consumed  shortly before the whale died and sank to the sea floor, the researchers report online today in the  Proceedings of the Royal Society B. Scales of such fish are rarely preserved in the rocks of that area, so those fish (which likely fed at or near the ocean’s surface, as their modern kin do) probably are the remains of the whale’s last meal and were expelled from the carcass as decomposition bloated the whale’s gut, the researchers propose. The size of the whale’s last meal—somewhere between 40 and 60 fish averaging 39 centimeters in length and together weighing between 16 and 25 kilograms—generally matches a stomach full of fish consumed by similar-sized modern-day relatives. The new find helps shed light on the evolution of beaked whales as well as their competition: Soon after M. gregarius swam the region’s seas, dolphins appeared on the scene, and their success in shallow coastal waters (where they now dominate), may have driven ziphiids to abandon foraging in surface waters.

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