How many people how many times have to explain to you what evolutionists actually claim so you can get on topic? Can you read?
It is about--corrected version here--the transformation claimed by evolutionists of the egg-laying reproductive system of mammals (like the still-extant monotremes) to the live-birth strategies of the marsupials and placentals. Mammals were mammals before they had any kind of live birth.
First, mammal-like reptiles diverged from other reptile lineages. That was far back, not long after the appearance of basal reptiles. Some lineages of mammal-like reptiles experimented with warm-bloodedness and with walking up completely on the legs (as opposed to dragging the belly and merely pushing with the legs).
Reptile ears aren't very good with the head out of contact with the ground. Thus, some of the high-walkers coopted their rearward lower jaw bones to resonate with the original reptilian earbone and enhance their hearing. This wasn't as hard as it may sound, since reptiles have losely-jointed, expandable jaws for swallowing large objects whole.
Eventually, this second useage of the rearward jawbones overwhelmed the original one. A "double-joint" allowed the use of a single bone for chewing and biting and completely freed the rearmost lower jaw bones for hearing.
This transition, well documented in the fossil record, is where taxonomists draw a line and say, "From here forward, we call them mammals." Admittedly, they pick this point as much because you can't see in the fossil record if a creature had mammary glands, or bore scales versus fur. (Fur isn't exactly diagnostic anyway as, for one thing, there's evidence for fur in pterosaurs, diapsid reptiles more related to dinosaurs than to mammals. But nothing else in nature has those ear bones.)
Later yet, some time after the monotremes had diverged from the basal mammal stock, mammals experimented with live-birth schemes. Marsupials are one result. Placentals are the latest and most successful.
Now do you understand what Dan Day's 378 is about?
How many people how many times have to explain to you what evolutionists actually claim so you can get on topic? Can you read?
How many times do I have to tell you that I do not accept what evolutionists claim? All the 'cr_evo' threads are essentially about whether the claims of evolutionists are correct or not.
The evolutionist claim is nonsense. We call the classification mammals, not three earboners for a reason. Further, as this discussion has shown, sharks have very diverse means of reproduction even though they are all fish. Since this discussion is about reproduction the fossil record is totally irrelevant to it and whatever bones EVOLUTIONISTS wish to call mammals is also irrelevant.