So http://www.imperial-library.info/category/tags/argonian it is said that argonians are oviviparous. Yet Ocheeva in Oblivion and I recall another argonian mention their younger selves as egg twins and hatchlings, which would imply that Argonians lay eggs, so how are Argonians truly born?

Argonians come in many shapes and sizes. I imagine some birth like mammals, while others lay eggs, and maybe both somehow. What's best about the Argonian race is how mysterious and alien they are.

They lay eggs I'm sure, there are referances and hints towards this throughout Oblivion. A flier for the Five Claws Lodge in Leyawiin (run by an Argonian) says something like "Leave the hatchlings at home tonight," you can't have a hatchling without an egg for them to hatch from.

My understanding is they do both, with Ovoviviparity being used in climates like, say, Skyrim or High Rock, and oviparity being used in their native Black Marsh.