They may not have changed noticeably, but that doesn't mean they haven't changed. You'd have to sequence a fossil and compare DNA to be sure.
I've met some evolutionary biologists who get rather tetchy when people throw around the terms "less evolved" or "more evolved". They seem to prefer talking about adapting to an environment over 'onwards-and-upwards' pinnacle-of-creation rhetoric. I suspect they would say the critter is just as evolved and evolving as anything else, just not much changed by it - presumably because the basic original design found a nice stable niche to entrench itself in.