Dugongs, along with manatees, make up a group of marine mammals called sirenians or seacows. In the modern world, only one species of seacow is found in any one place in the world. However, the fossil record of seacows, which dates back 50 million years, tells a different story. Researchers from Howard University and the National Museum of Natural History documented three different instances in the geologic past when it was more common to find three, maybe more, different species living together at one time. Their research has shown that each iteration of multispecies communities evolved from unrelated species of extinct seacows.