What was the third breed of dog?

There's no universally accepted concept of a "third breed of dog." Dog breeds are the result of selective breeding over centuries, and there's no specific order in which they arose.

Here's why the idea of a "third breed" is problematic:

* Dogs are all descended from wolves: All dog breeds share a common ancestor, the gray wolf.

* Breed development is ongoing: New breeds are constantly being developed, and the history of most breeds is complex, with contributions from multiple ancestral lines.

* No official "ranking": There's no official or scientific classification that ranks dog breeds by order of creation.

It's more accurate to think about dog breeds as a diverse and constantly evolving family, rather than a list with a clear order.