They are the largest animals present on the planet, and yet baleen whales do not really hunt for food and instead use the beards in their mouths to filter large amounts of seawater and nourish krill, other zooplankton, small crustaceans, and fish. However, these massive animals were once fierce enemies with sharp teeth, much like their cousins, the toothed whales of today.
Baleen whales or Mysticetes separated from their toothed cousins Odontoceten about 34 million years ago and researchers analyzed a whale skull from that time, which was salvaged from the Antarctic. The 34-million-year-old skull belongs to a whale ancestor species called Llanocetus denticrenatus.
"Llanocetus denticrenatus is an ancient relative of our modern gentle giants, such as humpback whales and blue whales, but unlike them he had teeth and was probably a formidable predator," said Felix Marx of the Royal Belgian Institute of Natural Sciences on Thursday Statement. Together with R. Ewan Fordyce at the University of Otago in New Zealand, Marx wrote a new paper on this topic.
Among baleen whales, the mouth has pronounced grooves containing blood vessels to feed the beard, which is itself strong but flexible material that acts like a sieve or a comb. Such grooves were also found in Llanocetus, but they grouped around tooth cavities. If this ancient whale had a bale, it could have been crushed between his teeth.
"Instead of a filter, it seems that Llanocetus simply had large gums and, according to the way his teeth are worn, was largely fed by biting prey, yet it was huge: with a body length of around eight meters it is comparable to living whales, "said Marx. [1
Fordyce and Marx suggested that Llanocetus had sharp teeth that were widespread along its rostrum, which it used to bite and prey on its prey scissors. Over time, the large gums developed into a complex shape that eventually became beards. But this transition only took place after the teeth were already lost and some whales had stopped biting prey and instead started sucking small prey. The beards may have first developed as a mechanism to better hold the swallowed prey in the mouth.
"Until recently, it was assumed that filter feed first appeared when whales still had teeth, and Llanocetus shows that this was not the case," Fordyce said in the statement.
The fact that Llanocetus lived at about the same time as the first Odontocetes was very happy, he added.
"Llanocetus is a combination of good fortune, in which the shape of the bones, small features that indicate the course of the soft tissues, and tooth wear tell a clear story." It is crucial that Llanocetus is also very old and lived exactly at the time When Mystizetes first appeared, it provides a rare window into the earliest phase of its evolution, "said Fordyce.
Her work entitled "Gigantism precedes filter feeding in the evolution of baleen whales", was published online Thursday in the journal Current Biology.
Today, toothed whales (like the killer whale) are much more species than baleen whales. Both species are spread around the world and face a variety of threats from human activity, including hunting, although it is largely banned.