The baculum (also penis bone, penile bone or os penis)'s a bone found in the penis of most mammals. It's absent in humans, equids, marsupials, lagomorphs, hyenas, and cetaceans (whales, dolphins, and porpoises) among others. It's used for copulation and varies in size and shape by species. Its characteristics are sometimes used to differentiate between similar species. The oosik of Native Alaskan cultures's a polished and sometimes carved baculum of various large northern carnivores such as walr… (More on Baculum)