Welcome to Atlantic!
I assume by looking for a "tamer guild", that you are more PVM, but I could well be wrong... If you really like the PVP aspect, please let us know here so we can better direct you!
Historically, I believe that the main Atlantic Tamer guild was "UTB - United Tamer of Britannia". Looking at the list on UO.com, it seems they are down to a minimal membership now - which saddens me... they were a great group!
Atlantic seems to have more general (little of everything supporting each-other) rather than specific purpose guilds (lots of one thing with support (like crafting) from other groups). My own guild of ODE tends to do a some of everything (except limited PVP), but we do have quite a few tamers (pretty much everyone has at least one) so it may be an option. If you are interested in a few trial hunts, drop me a PM!