Gnome Ranger with Riding Dog Companion

[clparis]

My Gnome Ranger had an issue in a battle royal in that I could not get away from the others due to my 20 foot movement. As I could see this as an adventure problem, I used the funds from my first adventure to buy a riding dog. I was thinking that I would have this dog become my companion in the future but as I look over the ranger list it appears that the dog companion is a small dog and the riding dog is a medium dog. So, my question is in society play will I have to get different companion or can I use the riding dog?

[Name Violation]

if you want a medium dog you gotta wait till effective druid level 4. you could take boon companion and be set as soon as you get a companion (or maybe a level later)