Baculum of a dog's penis; the arrow shows the urethral sulcus, which is the groove in which the urethra lies. Fossil baculum of a bear (Indarctos) from the Miocene The baculum (pl.: bacula), also known as the penis bone, penile bone, os penis, os genitale,[1] or os priapi,[2] is a bone in the penis of many placental mammals. It is absent from the human penis, but present in the penises of some pri
![Baculum - Wikipedia](https://cdn-ak-scissors.b.st-hatena.com/image/square/778efb882f60e6706009653b6acccbd85a89d59c/height=288;version=1;width=512/https%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fcommons%2Fthumb%2F3%2F3b%2FOn-the-Socio-Sexual-Behaviour-of-the-Extinct-Ursid-Indarctos-arctoides-An-Approach-Based-on-Its-pone.0073711.s001.ogv%2F640px--On-the-Socio-Sexual-Behaviour-of-the-Extinct-Ursid-Indarctos-arctoides-An-Approach-Based-on-Its-pone.0073711.s001.ogv.jpg)