Mammalian or something close. That's one advantage of the therapsid theory--some therapsids in Earth's prehistory may well have given live birth, and if they did, would have had a need to nurse their young. Even if the earlier ones didn't, or evolution didn't go quite
that far on Earth, it's very easy to imagine it going just a step further while still retaining other characteristics (like the scales) that might seem a bit more reptile-like, especially if their planet's climate is making it less necessary to evolve some of the things that mammals tend to have on Earth (like having fur cover their entire bodies).
Though one interesting observation--and I mean this in all seriousness. Cardassian armor, which is worn by both men and women, would seem to indicate that among Cardassian women, perhaps breasts don't tend to get as large as among some human women. (Either that or women bind themselves to be in uniform, which would be damn uncomfortable, but I knew someone in college who HAD to, because she was in Navy ROTC and it would have felt even worse to her not to when she ran or did other PT activities.) Notice that neither Natima Lang AND Iliana Ghemor had obnoxiously-sized breasts--very average, reasonable, and in proportion. True, we don't have a LOT of Cardassian women to compare, but I have to think that for Gul Ocett to wear the uniform she did, she couldn't have been that busty.