Baleen whales are huge, harmless filter-feeders. But 25 million years ago, a very different baleen specimen was terrorising the seas off Australia, tearing at its prey with large teeth.
The discovery of Janjucetus hunderi provides a new insight into the evolution of the two modern whale groups. These branches are baleen whales 鈥� which include blue and humpback whales 鈥� and toothed whales, which include the killer whale and the bottlenose dolphin.
Advertisement
鈥淭his provides us with a really good idea of what the most ancient baleen whales were like,鈥� says researcher Erich Fitzgerald of Monash University, Melbourne.
J hunderi was about 3.5 metres long, and with a skull measuring about 46 centimetres in length. If you saw it in the ocean today, you probably would not recognise it as a whale, Fitzgerald says.
The closest living analogue is something like a leopard seal. But the animal鈥檚 skull resembles those of pleiosaurs, marine reptiles living in the time of the dinosaurs.
Toothy grin
J hunderi鈥檚 eyes were huge, with sockets about twice the diameter of those of the bottlenose dolphin, which has a skull of a similar length. And it had a large set of teeth with no evidence of the comb-like fringes used by other baleen whales to filter their food from seawater.
Nevertheless, J hunderi definitely belongs to the baleen group. 鈥淭here are giveaway details in the ear region of the skull, for instance,鈥� says Fitzgerald. 鈥淭hese are unambiguous.鈥�
This new species is not the ancestor of modern baleen whales, however. The most ancient baleen whale fossil, found in Antarctica, is 10 million years older.
Instead, J hunderi belongs to an unrecognised evolutionary sidetrack, which no one had suspected existed.
A teenage surfer discovered the fossil on the central coast of the Australian state of Victoria in the late 1990s. It then languished in a student鈥檚 office at Monash University until Fitzgerald came across it and began the three-year process of carefully releasing it from its limestone block.
Journal reference: Proceedings of the Royal Society B (DOI: 10.1098/rspb.2006.3664)
