It's Breton, not Brenton.
Before men, mer and beast races there was only one humanoid species. I think they were called ehlnofey or something like that.
You mean Ehlnofey, ancestors of men, mer and beasts, as well as Tsaesci. Check out
Annotated Annuad, it's a description of how the world was created (I like the Khajiiti version better, but well
)
"On the world of Nirn, all was chaos. The only survivors of the twelve worlds of Creation were the Ehlnofey and the Hist. The Ehlnofey are the ancestors of Mer and Men. The Hist are the trees of Argonia.Over many years, the Ehlnofey of Tamriel became the Mer (Elves)On the other continents, the Wandering Ehlnofey became the Men: the Nords of Atmora, the Redguards of Yokuda, and the Tsaesci of Akavir."Words of Clan Mother Ahnissis tell us about the origins of Khajiit - they were once "forest people", one with mer. Azura changed them into beastfolk and tied them to the lunar phases. Y'ffre, from the same forest people, created Bosmer. This might explain why Ohmes and Ohmes-raht (subspecies of Khajiit) look so similar to Bosmer.
Argonians are something different altogether.
However, you're wrong in saying that there are ten races on Tamriel; there are many more, they just don't make an appearance in the game. Read here:
http://www.uesp.net/wiki/Lore:Races
Just to begin, Falmer, as you can see from the name, are elves as well and they actually still live in Skyrim.
Fishy87 explained the other races