50 million years ago, the creatures that evolved into whales were land mammals who had a carnivorous diet. Around this time they began to enter the sea and eventually evolved to become the marine mammals that we know as whales today. The first whales were all toothed, meaning that they had teeth and used them to hunt their prey. At some point, some whales began evolving to develop baleen plates instead of teeth, allowing them to hunt for smaller prey (krill, copepods, etc.) This type of feeding behavior is called filter feeding, and is still used by baleen whales today. Two recent fossil discoveries have uncovered two new species in the chain of this evolution, expanding our understanding of whales and the timeline of the evolution between toothed and baleen whales.
The first, Maiabalaena nesbittae, was found in Oregon, USA in the 1970‘s. The second, Toipahautea waitaki, was discovered in New Zealand in 1988. Updated technology and research methods have allowed both fossils to be recently reexamined by scientists. These two fossils have been determined to be some of the earliest known members of the baleen whale family. This makes them some of the earliest known ancestors to the minke whale and humpback whale, both of which are commonly seen around Iceland. They are also relatives to the blue whale, fin whale, right whale, and bowhead whale, which can also be seen at times in Icelandic waters.
Toipahautea waitaki dates back to approximately 27.5 million years ago, according to the study published in the Royal Society Open Science journal. Prior to this discovery the earliest known relative of baleen whales was the Mystacodon selenensis (roughly 36 million years ago), but still had teeth. The Toipahautea waitaki is the first discovery with a long, toothless jaw, and the study indicates that it had baleen plates and was a filter-feeder. There has been speculation that during the evolution from toothed to baleen whales, there was an ‘gap period‘ where whales had neither teeth nor baleen plates. Maiabalaena nesbittae confirmed this, as they had neither teeth nor baleen plates. The study, published in Current Biology, indicates that they were suction feeders and had a retractable tongue, allowing it to suck up small fish and squid.
Maiabalaena nesbittae was roughly 15 feet in length, and the Toipahautea waitaki was roughly 19 feet in length (about half the size of a modern minke whale). While there are some whales today that have very few teeth (like the sperm whale, which can suck it‘s prey up without chewing), all whales today have either teeth or baleen plates. Modern baleen whales are still filter feeders, and different species utilize different methods of filter feeding to catch their prey. Some whales use the skim-feeding method, where they swim with their mouths open at the surface to engulf their prey. Others use gulp-feeding methods, where they take huge mouthfuls of water and then squeeze the water out, leaving their prey trapped in the baleen plates. Whales today have more specialized feeding methods, but the studies indicate that the earlier ancestors were less specialized and likely used a variety of feeding methods.
These findings are incredible,and give us a more accurate timeline of the evolution of baleen whale species.They also fill in a evolutionary gap, and we now know that baleen whales lost their teeth before developing baleen plates. We still know so little about the ocean and the animals that live and have lived in it. As we continue to encounter new discoveries and our research methods improve, our understanding of whale behavior and development continues to expand. Who knows what discoveries will be made in the future!
For more information, you can find the articles here:
For more information on how modern baleen whales (like the humpback and minke whale) feed, check out this blog post from our friends at Special Tours: How do Humpback Whales and Minke Whales Feed?