Dictionary entry overview: What does reptile mean?
? REPTILE (noun)
The noun REPTILE has 1 sense:
1. any cold-blooded vertebrate of the class Reptilia including tortoises turtles snakes lizards alligators crocodiles and extinct forms
Argonians are the reptilian denizens of Black Marsh.
http://www.uesp.net/wiki/Oblivion:Argonian
Edit. adding link
come on man, think. THINK HARD. Argonians are a furry type race, so they can posses any human or reptilian trait that Bethesda finds convenient. How many times do I have to explain that when somebody invents a race of sentient beings, they can decide what they can and cannot do, for example Argonians can breathe underwater and on dry land, but they cannot be poisoned and Khajiit can (temporarly) see in the dark but they have problems harnessing magic to any real potential.
So really, if Bethesda wants to say "yup, they're warm blooded reptiles" then they
can because they invented Argonians. Get over it.
/le thread.