* Some species of fish: Certain fish, like seahorses and pipefish, have a pouch on the male's belly where the female lays her eggs. The male then fertilizes and carries the eggs until they hatch.
* Some species of spiders: Some spiders, like the wolf spider, carry their egg sacs in their jaws until they hatch. While not technically a pouch, this is a similar concept to external carrying.
It's important to remember that the pouch is a specific characteristic of marsupials, and while other animals may have similar strategies for carrying their young, these are not true pouches.