No, it wasn't. Or to be exact, we don't know, but it's highly unlikely. In 2009, the bone growth pattern of Myotragus was thought to occur only in cold blooded animals, but in 2012 they found it is widespread in extant mammals as well.

TIL there was a 5M year old cold-blooded mammal that humans killed off (but ofc).

Today I was reminded that science grows as new discoveries are made.

But we still killed the little beasties off. Nothing has changed there.