Monodontids, the group of whales that includes the belugas and narwhals swimming our ocean today, are emblematic symbols of the Arctic. However, their fossil record, although scarce, suggests that these animals' ranges could have been much broader. Fossil monodontids have been previously found in late Miocene deposits in Baja California, Mexico, the early Pliocene of Belgium and the eastern coast of North America.
Jorge Velez-Juarbe's blog
Sirenians, or seacows, are a group of marine mammals that include manatees and dugongs. In the modern ocean, only one species of seacow is found in each world region, however, the fossil record tells a different story. According to the fossil record of these marine mammals, which dates back 50 million years ago, it was more common to find three, maybe more, different species living together at one time. This oddity hinted that seacows’ environment and food sources were different than what we see today.