[packagingguy]

The hippocampus (pl.: hippocampi; via Latin from Greek ἱππόκαμπος, ‘seahorse’) is a major component of the brain of humans and other vertebrates.

https://en.wikipedia.org/wiki/Hippocampus

One could possibly make an argument that some invertebrates, and certainly jellyfish, are not conscious.

It’s quite doubtful that higher vertebrates such as birds and mammals do not have consciousness. Some like pigeons can pass the mirror test, which means they recognize themselves in the mirror.

Here’s a list of animals that can pass the mirror test:

https://science.howstuffworks.com/life/inside-the-mind/human-brain/animals-demonstrate-consciousness.htm

[ifinnegan]

“ It’s quite doubtful that higher vertebrates such as birds and mammals do not have consciousness.”

But they are conscious. Put a noxious chemical in their water and they will be conscious of it and swim away to avoid it.