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Reptiles that nourish their young via placentas?


Here’s New Scientist on reptiles that nourish their young via a placenta:

All live-bearing reptiles have a basic placenta, but unlike its mammalian counterpart the embryo doesn’t get much food that way. It can’t: although it nestles up against the oviduct wall, the embryo remains inside a remnant of eggshell that acts as a barrier. Instead, it is nourished by a large yolk.

A very few reptiles, including T. ivensii, break this rule. Their eggs are small, with little yolk, so they must get lots of food from their mothers via the placenta. But only T. ivensii allows the embryo to implant itself in the oviduct wall. “It’s unprecedented,” Blackburn says.

Not sure if that qualifies as a placenta, but it sure raises some questions.

Nick matzke:
Live birth has evolved dozens of times in reptiles,
More equivocation- Evolved how, Nick? Was it via: A) Front-loaded evolution B) Intelligent Design evolution C) Blind watchmaker evolution And how can we test the claim that live birth evolved from egg-layers? Or is it all unscientific hokum? Joseph
No surprise to this YEC creationist. its always been a wrong idea to classify creatures because of minor details or reproduction. I don't agree there are such groups in nature as reptiles or mammals. Yet surely defining creatures as placental has been a block to understanding biological relationships. i insist that marsupials are placentals with a pouch. Not wonderful examples of convergent evolution. There was no convergence nor evolution. Did evolution predict reptiles with placenta? Did evolution predict mammals with egg laying abilities.? I predict these classification ideas are headed for the same trash heap that will have Darwinian evolutionism. Creationists should take on the whole idea of convergent evolutionism as they must invoke it constantly to make things fit evolutionary theory. Robert Byers
Live birth has evolved dozens of times in reptiles, it shouldn't be surprising that in a few cases it has become particularly well-developed. Just because live birth is a key characteristic for mammals (well, except for the mammals that lay eggs) doesn't mean that it has any huge evolutionary status. IIRC there are some lizard species where live birth vs. egg-laying is a *within-species* polymorphism -- i.e., what is thought of as a "macroevolutionary" change is actually just a variable trait "within the kind" in this case. NickMatzke_UD
Certainly it qualifies as a placenta. There are species of fish that also use placental organs to provide nutrients, remove waste, and prevent autoimmune interactions between the mother and developing young. They are give birth to live, fully developed offspring. It shouldn't come as much of a surprise that some reptiles would be found using this same strategy for reproduction. Acipenser

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