New "Dreadnought" Dinosaur Most Complete Specimen of a Giant, via scientificamerican.com.
You can also view the original publication at Scientific Reports. (They've included a 3-D PDF of the bones in the supplementary information section, so if you have Adobe, you can take a look.)
Well, that happened to me yesterday when I was unexpectedly challenged on the subject of our friend above, one Dreadnoughtus schrani.
I say unexpectedly challenged, as I have grown somewhat accustomed to people smiling and nodding politely when I speak (especially when I speak excitedly); effectively tuning me out.
But as it turns out, theories abound and skepticism runs rampant when the subject of dinosaurs is raised.
Specifically, as it pertains to their age and the factors that led to their extinction.
It has been a very long time since I learned about carbon dating, and yes, I had forgotten about its limitations.
That's what happens sometimes, well for me anyway, I find I've incorporated certain things into an almost intuitive understanding; things I learned about and genuinely understood at one time, but when presently called upon to explain my understanding, I draw a blank. Needless to say, I realized it was time for a refresher.
1) Let's start with an easy one: What are fossils? (Source:Wikipedia)
"Fossils are the preserved remains or traces of animals, plants, and other organisms from the remote past."
2) What is carbon dating?
Radiocarbon dating is a tool used to date organic matter. The theory behind it is based on the fact that carbon 14, a radioactive isotope of carbon, can combine with oxygen to form radioactive carbon dioxide.
Specifically, as it pertains to their age and the factors that led to their extinction.
It has been a very long time since I learned about carbon dating, and yes, I had forgotten about its limitations.
That's what happens sometimes, well for me anyway, I find I've incorporated certain things into an almost intuitive understanding; things I learned about and genuinely understood at one time, but when presently called upon to explain my understanding, I draw a blank. Needless to say, I realized it was time for a refresher.
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| Silicified Fossils |
"Fossils are the preserved remains or traces of animals, plants, and other organisms from the remote past."
"The observation that certain fossils were associated with certain rock strata led early geologists to recognize a geological timescale in the 19th century."
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| Index Fossils by US Geological Survey |
Radiocarbon dating is a tool used to date organic matter. The theory behind it is based on the fact that carbon 14, a radioactive isotope of carbon, can combine with oxygen to form radioactive carbon dioxide.
And now, these molecules of radioactive carbon dioxide can begin to work their way through the food chain. Plants will use it for photosynthesis, and animals will eat the plants.
But then, when the organic matter dies (so to speak), it stops exchanging carbon with its environment.
And because the amount of carbon 12 remains constant, while the amount carbon 14 undergoes radioactive decay, this ratio can be used to date when the specimen stopped exchanging carbon. (Source: Wikipedia)
Other radioactive isotopes with longer half-lives can be used to overcome the limitations of radiocarbon dating when the age of the specimen exceeds 60,000 years.
As well, materials present in the vicinity of the find can be used as a referential time-frame.
Scientific American via YouTube
The detection of carbon 14 in the fossils of dinosaurs where it should not be present (> 60,000 yrs) has raised questions about the accuracy and reliability of radiocarbon dating. With some believing the dating is off by several million years.
3) How is it possible for organic matter to survive in excess of 60 million years?
Other radioactive isotopes with longer half-lives can be used to overcome the limitations of radiocarbon dating when the age of the specimen exceeds 60,000 years.
As well, materials present in the vicinity of the find can be used as a referential time-frame.
Scientific American via YouTube
The detection of carbon 14 in the fossils of dinosaurs where it should not be present (> 60,000 yrs) has raised questions about the accuracy and reliability of radiocarbon dating. With some believing the dating is off by several million years.
3) How is it possible for organic matter to survive in excess of 60 million years?
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| Tyrannosaurus rex |
In 2005, Dr. Mary Schweitzer and her team at North Carolina State University published a paper detailing how blood vessels and soft tissue had been found in T-rex fossils (~68 million years old).
The immediate response from the scientific community was to suggest the samples had somehow been contaminated. Still, there were others who greeted the news with Jurassic Park induced excitement.
And then there were those who interpreted the seeming impossibility of the discovery as lending further credence to the argument that specimens were being dated incorrectly.
In 2013 new research suggested an explanation for the controversial Schweitzer findings: "iron in the dinosaur's body preserved the tissue before it could decay." Well, what can I say? This was good news for the Jurassic Park enthusiasts!
Although extremely rare, there have been other cases of soft tissue fossilizing with bones. It indeed seems a matter of the conditions under which they met their end. In 2000, a team in Montana unearthed a somewhat mummified 77-million-year-old hadrosaur which had retained "traces of 80% of its skin, as well as other tissues and its stomach contents."
4) How did dinosaurs become extinct? (Source: pbs.org)
The most widely accepted theory, proposes that a giant asteroid struck earth some 65 million years ago. This theory is lent support by the presence of the rare element iridium, melted bedrock and fractured quartz in the Yucatan Peninsula where the impact is believed to have occurred. And also by the fossil record; which at present, points more strongly toward an abrupt rather than a gradual species decline. Oh and, I almost forgot, there's also that 150 km wide crater in the Yucatan Peninsula.
For the species which survived the initial impact, survival would have meant enduring an atmosphere of toxic soup, loss of food sources and habitat and extreme climatic events. It is estimated this led to the extinction of up to 70% of all plants and animals living at the time.
Other theories include: global volcanic activity, scarcity of resources, and an inability to adapt to ecosystem changes caused by continental drift.
UPDATES / RELATED
Original blood vessels in 80 million-year-old fossil / Science daily / December 1, 2015
How Dinosaurs Shrank and Became Birds / scientificamerican.com / June 12, 2015
Raging fires, high temps kept big dinosaurs out of North America for millions of years / news.sciencemag.org / June 15, 2015
Will Dreadnoughtus Dinosaur Lose Its Heavyweight Title? / LiveScience / June 10, 2015
Dinosaur blood cells extracted from 75 million-year-old fossil / NewScientist / June 9, 2015
How Dinosaurs Came to Rule the Earth / livescience.com / March 22, 2010
REFERENCES
Lamb, Robert. "How can soft tissue exist in dinosaur fossils?" 25 August 2010. HowStuffWorks.com. <http://science.howstuffworks.com/environmental/earth/geology/soft-tissue-dinosaur.htm> 05 September 2014.
Schweitzer, Mary H. (Sep 23, 1993). "Biomolecule Preservation in Tyrannosaurus Rex". Journal of Vertebrate Paleontology 13: 56A.
Schweitzer, Mary H.; Cano, R. J.; Horner, J. R. (Sep 7, 1994). "Multiple Lines of Evidence for the Preservation of Collagen and Other Biomolecules in Undemineralized Bone from Tyrannosaurus Rex". Journal of Vertebrate Paleontology 14: 45A.
http://news.sciencemag.org/2002/10/dinosaur-mummy-unveiledhttp://www.pbs.org/wgbh/evolution/extinction/dinosaurs/asteroid.html
https://www.youtube.com/channel/UCa37IMrH8BGS_pO6CKbTL-A
https://www.youtube.com/channel/UCOOi-Z1L_IXlPPWslhVJUTQ
https://www.youtube.com/channel/UCzWQYUVCpZqtN93H8RR44Qw
http://en.wikipedia.org/wiki/Fossil
http://en.wikipedia.org/wiki/Radiocarbon_dating
http://www.sciencemag.org/content/307/5717/1952.abstract
IMAGE CREDITS
"Silicified Fossils"
"Permian Silicified Sclerobionts" by Wilson44691 - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Permian_Silicified_Sclerobionts.JPG#mediaviewer/File:Permian_Silicified_Sclerobionts.JPG
"Index fossils"
"Index fossils" by United States Geological Survey - http://pubs.usgs.gov/gip/geotime/fossils.html. Licensed under Public domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Index_fossils.gif#mediaviewer/File:Index_fossils.gif
"Tyrannosaurus rex"
"Palais de la Decouverte Tyrannosaurus rex p1050042" by Copyright © 2005 David Monniaux - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Palais_de_la_Decouverte_Tyrannosaurus_rex_p1050042.jpg#mediaviewer/File:Palais_de_la_Decouverte_Tyrannosaurus_rex_p1050042.jpg
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