Central Africa’s Lower Congo River is home to an extraordinary assortment of fish—many truly bizarre. This  video by Science Bulletins, the American Museum of Natural History’s current-science channel, features Museum scientists on a quest to understand why so many species have evolved there. It provides an excellent case study of allopatric speciation and helps to dispel the myth that populations only ever become isolated on islands. A Google Form worksheet to accompany the video is available here.