Test shows dinosaurs survived mass extinction by 700,000 years

Jan 27, 2011

University of Alberta researchers determined that a fossilized dinosaur bone found in New Mexico confounds the long established paradigm that the age of dinosaurs ended between 65.5 and 66 million years ago.

The U of A team, led by Larry Heaman from the Department of Earth and Atmospheric Sciences, determined the femur bone of a hadrosaur as being only 64.8 million years old. That means this particular plant eater was alive about 700,000 years after the many paleontologists believe wiped all non-avian dinosaurs off the face of earth, forever.

Heaman and colleagues used a new direct-dating method called U-Pb (uranium-lead) dating. A laser beam unseats minute particles of the fossil, which then undergo isotopic analysis. This new technique not only allows the age of fossil bone to be determined but potentially can distinguish the type of food a dinosaur eats. Living bone contains very low levels of uranium but during fossilization (typically less than 1000 years after death) bone is enriched in elements like uranium. The uranium atoms in bone decay spontaneously to lead over time and once fossilization is complete the uranium-lead clock starts ticking. The of lead determined in the hadrosaur's femur bone is therefore a measure of its absolute age.

Currently, date using a technique called relative chronology. Where possible, a fossil's age is estimated relative to the known depositional age of a layer of sediment in which it was found or constrained by the known depositional ages of layers above and below the fossil-bearing horizon. However, obtaining accurate depositional ages for is very difficult and as a consequence the depositional age of most fossil horizons is poorly constrained. A potential weakness for the relative chronology approach is that over millions of years geologic and environmental forces may cause erosion of a fossil-bearing horizon and therefore a fossil can drift or migrate from its original layer in the strata. The researchers say their direct-dating method precludes the reworking process.

It's widely believed that a mass extinction of the dinosaurs happened between 65.5 and 66 million years ago. It's commonly believed debris from a giant meteorite impact blocked out the Sun, causing extreme climate conditions and killing vegetation worldwide.

Heaman and his research colleagues say there could be several reasons why the New Mexico hadrosaur came from a line of dinosaurs that survived the great mass extinction events of the late Cretaceous period (KT extinction event). Heaman says it's possible that in some areas the vegetation wasn't wiped out and a number of the species survived. The researchers also say the potential survival of dinosaur eggs during extreme climatic conditions needs to be explored.

Heaman and his colleagues believe if their new uranium-lead dating technique bears out on more fossil samples then the KT extinction paradigm and the end of the dinosaurs will have to be revised.

Explore further: Ancient human bone reveals when we bred with Neanderthals

More information: The research was published online, January 26, in the journal, Geology.

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User comments : 16

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bwvandorn
5 / 5 (1) Jan 27, 2011
This is not a new dating method. U-Pb is one of the oldest and most refined of the radiometric dating schemes. Loss (leakage) of lead from the sample will result in a discrepancy in the ages. Leakage is more likely during fossil migration. U-Pb dating is most accurate in a closed system.
SincerelyTwo
2.1 / 5 (11) Jan 27, 2011
Next we'll discover we mis-calculated when the mass extinction event took place, it was 700k years later than expected.

That or the extinction even practically did kill the dinosaurs, the rest would be hunted out of existence soon after.

etc etc etc, tolerance for error, etc etc etc

Come on, if you're a scientists you've got to be smart enough to realize that it's -your data- telling you this information; which by no means gives you the right to say it's an objective fact that events took place as the information states. It's a scientific fact that all these tools for measurement are not absolutely reliable or precise.

etc etc lots of obvious stuff, etc etc wtf is wrong with the world ... etcetc
Skeptic_Heretic
5 / 5 (2) Jan 27, 2011
Heaman and his colleagues believe if their new uranium-lead dating technique bears out on more fossil samples then the KT extinction paradigm and the end of the dinosaurs will have to be revised.
Exactly where and when in New Mexico was this bone found?
sstritt
2.3 / 5 (3) Jan 27, 2011
Robert Bakker never believed in the KT extinction event. He hypothesized that the dinos were in serious decline before the asteroid impact. Besides, the birds survived, so why not a few other species of dino?
plaasjaapie
2 / 5 (4) Jan 28, 2011
Years ago, dinosaur teeth were discovered in stream beds laid down several million years after the KT event. These were duly reported in the literature and largely ignored thereafter. It's nice to see further confirmation of the existence of relict populations of dinosaurs after KT.
Johnny_Morales
3.6 / 5 (5) Jan 28, 2011
Despite it being mindlessly repeated in the mass media that an asteroid killed the dinosaurs as if it is a settled issue, it is anything but.
It's far from proven, but the dramatic nature of the theory keeps it alive.
It also is one of the classic examples of researchers desire for something to be true is so strong, that all evidence to the contrary is summarily dismissed while the most outlandish interpretation of the evidence there is is used to promote the killer asteroid theory.
Imagine what they might find if all the minds spending all that time trying to prove something that can't be proven look for other reasons.
meerling
2 / 5 (1) Jan 28, 2011
Scientists are supposed to fit theories to the facts, and in the process of analysis and discovery they debate all aspects of the data and theories. Yet they are human and far too often get hung up on defending stuff they've worked so hard to defend in the past even though there is new information that calls the previous work into question.

So they're human. All sides need to remember that and not get so bloody defensive of ideas that upset the applecart of tradition.
Jimbaloid
5 / 5 (4) Jan 28, 2011
So 65.5 million years becomes 64.8 million years, I'm not about to get particularly excitable over ~1%. Dinosaurs lived, and later they went extinct. Perhaps most of them were already gone by 65.5 anyway. I had always assumed that there must have been some who clung on well after the rest - the planet wasn't sterilised, life continued, no one has suggested they all died at some rigid precise moment? For me this doesn't change anything, just adds some richness to the data, of which I'm sure there will be more to come. For those that are debating what this means for scientific methods, remember that at this point it is also a single data point, a single bone.
Mayday
not rated yet Jan 28, 2011
This really upsets the classic sic-fi interpretation of a single dramatic event wiping out thousands of species before lunch. Who doesn't cherish that long-held image of the dinosaurs looking up, mouths agape, at the blazing fireball about to incinerate their butts? I'm glad to hear that maybe a few of them looked up and went "meh." It is much, much more believable. But dramatic sic-fi simplicity is hard to debunk. Good luck with this.
jmcanoy1860
1 / 5 (4) Jan 28, 2011
Not a single cretinist diatribe?
Bog_Mire
5 / 5 (2) Jan 28, 2011
I think you will find he has impaled himself on tidal forces in another blog.
rgwalther
not rated yet Jan 28, 2011
NOT all of them!
Paljor
not rated yet Jan 28, 2011
oh yes all of them look up "fizzy ocean on encleadus) ((is that how you spell it?))
brentrobot
not rated yet Jan 29, 2011
Perhaps the aftermath of the "extinction event" led to the rapid evolution of small mammals more capable of hibernating and digging holes. Its not hard to imagine a bunch of little vole or mole like creatures digging tunnels and feasting on the very large eggs of dinosaurs.
Moebius
2.3 / 5 (3) Jan 30, 2011
They are gone, there must have been an extinction event whether quick or protracted. Birds, reptiles and we are here, some must have survived. The KT boundary exists almost everywhere, there must have been a big hit at least once and there isn't only one of too many things, if any. I'm more interested in if we are going to be smart enough to survive the next one than quibbling about minor details.
Ethelred
not rated yet Jan 31, 2011
Here is a link to the Geology article's abstract. Costs money to read the article.

httpDELETEME://geology.gsapubs.org/content/39/2/159.abstract

Based on that abstract they tested fossils both above and below the boundary. The fossil in question was from above the boundary and thus is likely to have been from a survivor unless the fossil moved up from below over the last ohh 64.8 million years or so.

Looks like it might have been a survivor.
directly date two dinosaur fossils from the San Juan Basin of northwestern New Mexico and southwestern Colorado, United States.
Which places it a bit distant from the Chixalub impact. Closer to the Gulf of Mexico and I would have more serious doubts. Anywhere in North America short of Northern Canada or Alaska leaves me with some doubts.

Very interesting.

Ethelred