posted
Excerpt from Today's Washington Post <subscription required>
quote:
Fossil's Bone Tissue Points to Sex of T. Rex
By Guy Gugliotta Washington Post Staff Writer Friday, June 3, 2005; Page A03
...The Hell Creek female, discovered beneath 1,000 cubic yards of sandstone in northeast Montana, is rapidly becoming one of the most famous dinosaur fossils ever found. In March, the Schweitzer team announced that a thighbone, or femur, from the specimen, a young adult about 18 years old when it died, contained soft tissue that had survived for 70 million years.
"It's an outstanding fossil," said team member John Horner, curator of paleontology at Montana State University's Museum of the Rockies, where the remains are being studied. "And the likelihood of finding another dinosaur with this kind of material is really low."
Schweitzer said the discovery reported today came during the team's examination of the same cross section of femur that eventually produced the soft tissue. Horner said a thin, spongy-looking layer of bone lining the femur's inner cavity was visible to the naked eye and had clearly been permeated with blood vessels when the creature was alive.
The team reasoned that the tissue was "medullary bone" similar to that formed by female birds today when ovulation begins the egg-laying cycle. Schweitzer said the bone is an "ephemeral feature," a reservoir of calcium deposited in the bone cavity and drawn upon to build eggshells. As the T. rex laid eggs, the medullary bone depleted and finally disappeared, as it does with modern birds, at the end of the cycle.
This got me wondering what paleontologists are saying about the soft tissue finds. Are the revising (far downward) the age of dinosaur fossils? Or, have they figured out ways that the soft tissue might have been preserved for 65+ million years?
Well...in a brief search, I found the following:
1) The "soft tissue" isn't the same as soft tissue one would find in a more recent vintage corpse. It was pliable upon rehydration and treatment with a weak acid. Still, for 65+ million years, that's astonishing.
2) The researchers don't know the composition of the tissue. Given that it was inside a fossilized bone, the question of how this normally 'eaten' material survived is still open. Typically, bacteria will devour all the soft tissue and inside of bones is not a particularly difficult barrier to get through because there are holes to pass through.
3) The researcher noted an odor "like embalming fluid" when the bone was opened. This might be a clue. As many originally speculated, the chemical environment in which the fossil was embedded may have had something to do with the way the internal tissues were apparently preserved.
4) Still no clue if this is a rare event or pretty typical of fossils collected in various environments. No-one has taken Jack Horner's advice and gone through their dino-collections cracking open femurs.
So...for now, still up in the air, but some theorizing is going on about how this stuff might not be the same as preserved original tissue and some theorizing about how it may have happened based on local conditions immediately after death.
At any rate, we know know the sex of at least one T-Rex.
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posted
Have they been able to do DNA studies with the soft tissue? I would think that would help with the whole birds/dinosaur discussion.
Posts: 2207 | Registered: Oct 2003
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posted
I had the impression that this was definitely not the actual tissue, but a cell-by-cell replacement with some kind of pliable material. So DNA would definitely be out of the question.
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posted
I wonder if an MRI could be performed on dinosaur femurs to get a better idea of what's inside, although I suspect that there may be a lack of water or other hydrogen-containing substances inside.
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I suspect they could try rehydrating through immersion of the entire bone/fossil in a proper solution, then do an MRI. Although I'm not sure if this would work since the process of fossilization might close up any pores that were there in the original bone matrix. Hmm...
I would think they could use sound waves to tell if the thing is at least hollow. The presence of a cavity (or marked density change) would probably be a good indication of at least a possible.
Overall (weight per cubic meter) might tell them something too. I mean fossils are pretty heavy if they are mineralized throughout, right?
Heck. I don't really know... Just speculating.
Posts: 22497 | Registered: Sep 2000
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posted
Is the Hell Creek dino the same as Sue here in Chicago? Because today's Tribune reported that scientists finally proved that she was female and actively reproducing.
Posts: 4515 | Registered: Jul 2004
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Goody, I don't think Horner ever got a chance to study Sue. I think she was mainly studied at UCLA before the Field Museum bought her. I'll have to ask my expert tomorrow.
Posts: 2711 | Registered: Mar 2004
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1) It's the largest T-Rex skeleton yet found, 2) No idea what sex 3) They think Sue's age was around 28 years (which was considered "old." 4) Hasn't been looked at for soft-tissue content
alluvion -- I'm not sure what you mean. Bogus implies that they lied, fabricated, or have gone way beyond the facts and observations. All they've really done is a bit of comparative anatomy (in this case, the analog is modern birds) and seen that a structure that forms during egg-laying is present in this one T-Rex's remains, and they haven't seen it in others.
It's a fairly rare event, they believe, to have a fossil from an animal that died during egg laying. In fact, most of the T-Rex skeletons show signs of arthritis, signaling that they were probably beyond reproductive age or at the tail edge of their reproductive years (at least if they were female).
All of this stuff is conjecture based on what we know about living reptile species and in comparison to other species we can study now.
The funny thing is, the more we learn about dinosaurs, the more they seem like bird species, especially ones like the emu. That doesn't mean that everything is the same, or that the analogy shouldn't be limited somewhat (e.g., did they have 4 chambered hearts?) There's a lot that isn't known and may never be known.
But that doesn't stop educated people from making some pretty good guesses. Some of those guesses can be tested against the existing fossil record and/or tell us what to look for in new fossils.
It's not just cool conjecture. It's also a great deal of hard work and passing through a gauntlet of peer review.
It could be that the coverage of it in popular media trivializes it, but that's not the researchers' fault if that happens. I do find that the major newspapers have pretty decent science editors (NYTimes, Washington Post, London Times, etc.) But stuff that gets picked up from AP service is often just not worth reading.
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posted
I visited a guy in federal prison who served time with the guy who dug up Sue. It was so weird because they put this guy away for digging up the skeleton improperly (I think his method was okay, but somehow he ticked off the FBI), and at the end of the trial it belonged to the guy who owned the land they dug it from. (Whom they had paid $5,000 which is probably too low, but still...)I mean, it seems in that case it should have been a civil trial. But I don't know. There was this nova program about it. The thing is, the land owner wound up selling it anyway.
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