Probably not canon, but if you're familiar with the Docker logo (a blue whale carrying shipping containers on its back) it made me think of a kind of living cargo ship. It would be like a combo of a whale and a turtle, or rather a fish and a turtle. It wouldn't be closely related to land animals and would have gills rather than lungs.

In the wild it lives in schools/pods. Individuals take turns floating at the water's surface, letting algae and such grow on the shell on their back, then dive down and let the other pod members eat whatever grew on the shell.

Yinrih tame/domesticate them, breed them to have flat shells that can act like a ship's deck, and use them to haul cargo. Maybe these guys would be part of the hexapod clade, or a related clade.

I just recreated Lapras didn't I…