I'm aware of that. But, for where I lack awareness, I'm using "strawman" for a misrepresentation of one's own argument to make it easier to defend. Maybe bait-and-switch would be better, but even that really doesn't fit. Maybe non-sequitur. Because dinosaurs laid eggs, they're ancestors of birds. Because flies lay eggs, they're ancestors of birds (I know, not as parsimonious).
Where did anyone in this thread argue that dinosaurs laying eggs is evidence for evolution? You're argueing against a straw man here.
Fundamental changes seem to always be poorly documented in the fossil record.
Actually there are many nice transitional series for things which involve bones, such as the series which i listed here earlier. It's an excellent example for the change of the skull structure, including the development of the middle ear during the transition from reptile to mammal.
But how do you expect things which are mostly a soft tissue thing to be visible in the fossil record? Considering how rarely soft tissue is preserved, does it really surprise that this is sketchy at best?
I suspect it's an insurmountable hurdle (low fitness) for a body to hold a developing egg for an extended period of time, just to still lay an egg. There's the burden of carrying the egg without corresponding benefit.
What about not having to protect a nest at a fixed location? It greatly enhances the mobility during gestation.
If there was only a decisive negative aspect to it, mammals should be extinct by now, shouldn't they?
The presence of the egg shell is the only real difference. And by the way, reptile eggs aren't hard but rather leathery - and the babies of mammals still grow in amniotic sacs which may very well be the successors of that.
It's almost a necessity to jump from eggs to live birth (even if fairly premature). Then, the mammery system still needs to be created.
As indicated by the platypus, mammary glands came before live birth. And besides, these are two completely seperate things, one can have live birth without mammary glands and vice versa.
Since both concepts are successful. what would be an actual problem with a hybrid version?