I just bought Infernal City yesterday, and am only a third through it, but I have noticed a few moments where Greg Keyes mentions things that don't exactly sound like they fit into TES.
An example would be when (spoilers, by the way) Anna?g is saved by Glim from that boat that's meant to take her to Cyrodiil, and she holds on to him while he swims to the shore.
One of the lines reads: "On land, Glim was strong, but here he seemed really powerful - a crocodile, a dolphin."
Now, as far as I'm aware, that would be the first time dolphins have ever been mentioned in TES. There have been several moments like this in the book already, and, like I said, I have only read part 1 so far. I just wanted to ask if this kind of stuff should be considered official lore, or if little things like using a real world animal to describe something doesn't mean that animal actually exists in the TES universe. This wouldn't really bug me as much if it wasn't so frequent, or if he sometimes created some kind of fantasy creature to explain something, but it happens relatively frequently and always throws me off.

Real animals exist in TES, so its not that odd I suppose, and Infernal City is indeed canonical weather we like certain parts of it or not.