sciencehabit writes "Thanks to a highway-widening project in California's Laguna Canyon, scientists have identified several new species of early toothed baleen whales. The new fossils date to 17 to 19 million years ago, or the early-mid Miocene epoch, making them the youngest known toothed whales. Three of the fossils belong to the genus Morawanocetus, which is familiar to paleontologists studying whale fossils from Japan, but hadn't been seen before in California. These three, along with the fourth new species, which is of a different genus, represent the last known occurrence of aetiocetes, a family of mysticetes that coexisted with early baleen whales. Thus, they aren't ancestral to any of the living whales, but they could represent transitional steps on the way to today's whales."