I wish they would have elaborated on the statement from the first paragraph. It would be interesting to here how it is known that the creature is a sea creature, as well as how it is know that it was an air breathing creature. It would also be nice to here how the fossils was aged and how the previous assumption was formed.

Clarifications on those topics would enable a reader to feel more comfortable that we will not one day read about a false assumption that the air breathing sea creature was once born on land.

Get a book on dinosaurs, dude. My 5 year old can point out the differences between an ichthyosaur and a terrestrial dinosaur.

Sea turtles are air breathing sea creatures that are born on land. Why would you think that this isn't a reasonable assumption?

Why would you assume that I thought this was not a reasonable assumption?

"Clarifications on those topics would enable a reader to feel more comfortable that we will not one day read about a false assumption that the air breathing sea creature was once born on land." I could be terribly misreading your comment, but this seems to imply that you are uncomfortable about it.

To respond to your question of how the fossils are dated, they're found in the early Triassic strata, and for creatures that old it's the strata (not the fossils) which are radiometrically dated. Geologists have a few different methods, but Uranium-Lead (U-Pb) decay is probably the most accurate for that time scale. There are other methods like Potassium-Argon (K-Ar) and Rubidium-Strontium (Rb-Sr) which would be used to ballpark.

I was not asking what methods of aging are available. I understand the options. I was interested how this particular fossil was dated. I also understand that there are air breathing sea creatures that are born on land. Why would I think this is one as well?

You can read the article here: http://www.plosone.org/arti...

The fossils were, like I said, dated by the stratum they were found in: "All three specimens are from near the bottom of the Subcolumbites zone of the Middle Spathian (Lower Triassic)." The Subcolumbites zone is dated to ~247 Mya.

All reptiles breathe air through lungs. As far as it being born on land, the article is a bit shaky on that. The rock that the fossil was found in was marine, so the authors state that the creature most likely died in labor *underwater*, and that it can't be firmly established from this whether or not this species gave birth on land or in the oceans (so, technically, the NPR article is incorrect on that). They do establish that the likelihood of the three embryos being breeches is extremely low, so it's likely that this species gave birth head-first, which is extremely unusual in obligate marine creatures although possible. This is taken as evidence that chaohusaurus's genetic ancestors most likely gave birth on land, although chaohusaurus itself may or may not have. Later icthyosaurs gave birth tail-first like most air-breathing underwater creatures.

Mr. Foster, are you a guide/docent at Mr. Ham's Creation Museum in Kentucky?

It's an ichthyosaur, i.e. a marine dinosaur. Dinosaurs were all air breathers, and marine dinosaurs' legs all evolved into flippers, which provided propulsion in water but not on land. The same thing happened with marine mammals, which started out as terrestrial ungulates (hoofed animals) but whose forelegs evolved into flippers and whose hind legs were lost entirely as they adapted to an aquatic existence. The first part of "ichthyosaur" is from Greek ichthys ("fish"); this type of dinosaur gets its name because its body is shaped like that of a fish. I wouldn't hold my breath waiting for the falsification of that assumption you're talking about.

I don't think it's really fair to demand all that elaboration from a blog. The work is published in an open access article that you're free to read, and it in turn references plenty of other resources so you can learn more. There's something like 170 yrs worth of research on marine reptiles (they're not actually dinosaurs, though they were contemporaries; some other comments seem to confuse this point), and if we demanded detailed accounting of every well established finding from our news sources, I don't think we'd ever get through to the end.

Anyway, as a quick summary, fossils of these animals are found in regions where the corresponding strata were covered by ocean when the animal was fossilized. They have flippers and streamlined bodies suited to swimming. They descended from terrestrial, air-breathing reptiles, lacked gills, and had nasal openings for breathing through their lungs like their ancestors. If you're not comfortable with any of that, I'd encourage you to do some further reading and draw and informed conclusion.

Orange? Yellow? Have I suddenly been struck color-blind?

The editors who posted the picture cut off the bottom half of it explaining things. http://www.plosone.org/arti... <-- The caption above is referring to Fig. 2 here.

may the animal died because it gave birth head first ?? may be it is not natural to give birth head first this animal. Any thoughts ??

It's a marine air-breathing animal. If it gave birth to its offspring headfirst in the water, the baby would drown. This is why cetaceans give birth to their young tailfirst. The calf continues to get oxygen through the umbilical cord while it is emerging. A kink in a human umbilicus can cause what is called perinatal anoxia (oxygen starvation during delivery). Babies delivered this way ordinarily suffer serious brain damage and would be unable to live without very expensive care paid for by the obstetrician's medical malpractice carrier. Marine dinosaurs didn't have liability insurance.

Yesssssssss!

Sometimes they just don't go through (it happens to me often). If it was deleted there'd be a note in place of the post. Otherwise I think you just have to give it whole minutes after you hit the "Post" button before reloading or leaving the page.

thnx David L!
I appreciate the fast response, bro!

I've always wondered where they get the silicon for their silicone skins. The silicon content of human prey is almost nonexistent.

The upvotes mostly come at night... mostly.

cuz yur pretty.

people like references to '70's movies?

Because you beat a bunch of people to the punch!

And did that prehistoric birth on land have a choice of sexual preferences?

Just the FSM planting more evidence with His Noodly Appendage.

"may have"

And that to NPR means "did". Yeesh.

Yeah, reading the PLOS paper itself leaves a lot more room for debate.

by 250 million years ago you mean like 6,000 right?...lol

sounds like somebody was trying to hide a little stepping out.

Amazing!

Wow. Thanks. Science is fascinating stuff.

Hooray! They found Godzilla's mamma!

Wow, the fossils they are making these days are beautiful.

more proof that in the chicken/egg debate the egg came first.

? What.? Wouldn't this be proof that the chicken came first? A live birth indicates....no egg.

this shows that the first chicken egg was laid and cared for by a creature that was not a chicken. hence, the egg came first.

?What? How does it show that the animal caring for the chicken egg is not a chicken?

because the chicken evolved out of a non-chicken. a non chicken gave birth to the first chicken. so the egg came first.

If a non chicken gave birth to the first chicken.....where's the egg? The chicken came first.

the first chicken egg was laid by and cared for by a non-chicken. so the egg is first!

You said....gave birth to the first chicken.....which implies birth....not egg laying.

Also, this fossil does not show an egg. Assuming the birthed "chicken" would have survived this experience....why do you think it would have laid an egg?

ok a non-chicken laid an egg that then hatched into a chicken. so the egg is still first. some surviving chicken then had to lay the second egg etc.

I still don't understand where you get the egg from based on this fossil find.

You claim a non-chicken that normally births their offspring somehow became an egg layer and on top of that, the hatched egg was a chicken...not a non chicken. It's also confusing since there is no egg laying taking place in this fossil find.

I just mean that in evolution one animal gives birth to a different kind of animal. everything started in the sea., then one day a sea creature gave birth to a land one. or laid eggs or whatever. in this way whatever evolved into a chicken had to in fact produce a chicken. since it did so via an egg, the egg came first.

LOL. Nothing you said explains why the chicken.....came from an egg. Maybe the chicken was born from an actual birth (like the fossil shows) and that eventually that chicken evolved into something that lays eggs instead of live births.

you mean a chicken from a live birth produced an egg? no that isn't right. if the chicken in your example evolved into a chicken it wasnt a chicken to begin with which is my point..

Wait. Is it because it looks like a chicken being born? No...that would mean the chicken came first.