It's a common feature among Chondrichthyes, the cartilaginous fishes (including sharks and rays and other related species). Though in some species only one of the paired uteri is functional.
It's a common feature among Chondrichthyes, the cartilaginous fishes (including sharks and rays and other related species). Though in some species only one of the paired uteri is functional.
Well, for sharks that give live birth (directly w/wo placenta or via eggs hatching internally), if both uteri are functional then usually both can bear young at the same time. Different fathers are possible (and is often the case). Notably, in the case of the tawny nurse shark, the young can even swim between uteri, which they do to *ahem* feast on unfertilized eggs.
In some sharks, however, only one of the uteri is functional. The other is a vestigial organ (like the human tailbone) and is usually completely nonfunctional, so the shark effectively only has a single working uterus.
