Scientists carrying out projects in California’s Laguna Canyon have identified several new species of early toothed baleen whales. Amongst the scientists were palaeontologist, Meredith Rivin, and archaeologist, John D.Cooper, who presented their findings in Fullerton Centre, California.
When the Laguna Canyon outcrop was excavated between 2000 and 2005, it delivered the remains of hundreds of marine mammals that lived 17-19million years ago; 30 cetacean skulls and other ocean dwellers, alongside which were the four newly discovered species of toothed baleen whale. Whales comprise of odontoceti (toothed whales such as dolphins and killer whales) and mysticeti (baleen and filter-feeding whales such as the blue and humpback). It is thought that the toothed and baleen whales share a common ancestor, despite scientists believing that the latter became extinct 5million years earlier.
The fossils were excavated a decade ago, but because unveiling answers buried deep within rocks is such a lengthy process, it has only just been formulated that one of the species – names ‘Willy’ – is much larger than the others. So large, in fact, that the levels of tooth decay indicate that it may have predated upon sharks.
All modern whales evolved from a single land mammal over 55million years ago and were quite small, and so one big question remains: how did they evolve to become so gigantic? Nicholas Pyenson (Live Science) suggests that one possible explanation stems from the ‘development of the baleen to lunge feeding’ which is a process where ‘the whales swallow large quantities of water and filter out small animals’.
‘Baleen’ refers to the frayed plates that line the jaws of the whale, which aid in the filtering process of their feeding habits, and so an interesting discovery was that early baleen whales actually had teeth. In present day baleen whales, teeth still develop within the foetus, but are reabsorbed before the enamel has chance to form. Rivin states that: ‘the new fossils date to the early-mid Miocene epoch, which makes them the youngest known toothed whales’ (Huffington post).
All four of the whale fossils found mark the last known occurrence of aetiocetes (mysticetes that coexisted with early baleen whales), and although they aren’t ancestors to any living whales, they could represent the key transitional steps to the formation of toothless mysticetes of today.
It is not yet clear what Rivin’s team will reveal about the early evolutionary past of the baleen whale, but it is hoped that their findings will be published by the end of the year.
Scott Donald, Flickr Creative Commons