The evolution of whales is one of the most intriguing stories in natural history. Shortly after the extinction of the non-avian dinosaurs, mammals diversified to fill the niches that were left by their reptilian predecessors. Some of those mammals took advantage of the abundant resources found in the shallow water. Over time, evolved such a dependency on their new habitat that they would lose their limbs. These were the first whales, which appeared a mere 10-15 million years after the K/Pg extinction – an incredibly short amount of time for such drastic changes in morphology and physiology.
The most specialized whales are undoubtedly the baleen whales. These marine mammals are characterized by a highly specialized tissue growing from their palates. They lost their teeth in favor of keratinous gum tissue which has evolved into massive walls of bristly, thin plates called baleen, or whalebone. These huge rows of baleen act as sieves, straining out tiny prey such as krill and baitfish from the water. This feeding strategy, engulfing whole shoals protein in one mouthful, has led to the massive size of these whales – the blue whale, a filter-feeder, is not only the largest whale and the largest mammal, but the largest animal to ever live.
Paleontologists from New Zealand have recently identified a pair of ancestral baleen whales, and have shown that this remarkable adaptation evolved not very long after true whales themselves evolved. They belong to the new genus Tohoraata, represented by two species: T. raekohao and T. waitakiensis. These whales, members of the extinct family Eomysticetidae (the “dawn mysticetes”, Mysticeti being the modern order of baleen whales), lived in the shallow, warm waters of Zealandia 27-25 million years ago, during the Oligocene.