A native species featured in the Cyantian Chronicles sci-fi series. They're semi-aquatic, with gills on their lower torso and a marsupial-like pouch
At the time of writing this description, the wiki page about them is broken, but may be fixed at some point: http://shivae.com/cyantian/index.php?topic=935.0
The land-dwelling native species page is here, featuring a link to the rifier page (which is throwing an error right now) https://www.shivae.org/wiki/index.php/Category:Land_Dwellers