Is a sea lion a Pinniped?
A sea lion is definitely a pinniped.
The biggest difference is that the second one of them actually exists. The merlion is a mythical creature something like a mermaid, but involving a lion rather than a human. It should not be confused with the sea lion, which is an actual creature that isn't much like a lion at all, but a pinniped, closely related to the true seals and the walrus.