Molecular Palaeontology - Dinosaurs & Birds
Saturday, 26. April 2008, 15:53:06
Julia (The Ethical Palaeontologist) has already commented on the Science article Molecular Phylogenetics of Mastodon and Tyrannosaurus rex here and here.
There is not much meat on the article itself, it is just one single page, so it may be no surprise, that the media add lots of feathers. Never the less I found the article quite interesting because of the method used to confirm the relationship between dinosaurs and birds.
Evidence of close evolutionary relationships among birds and non-avian dinosaurs have been accumulating for a long time. See a.o. my post on the Archaeopteryx - probably the most famous fossil, and considered an important link between dinosaurs and birds.
In 2005 it became known that a group of dinosaur researchers had discovered soft tissues in fossil Tyrannosaurus rex bone unearthed in 2003 by Jack Horner in the Hell Creek Formation in Montana, USA. As the bone was 68 million years old it is surprising to have found still elastic soft tissues looking like blood vessels and cells. We are not talking Jurassic park and no DNA could be analysed. By using mass spectrometry protein sequenced from collagen were however detected. Collagen is a protein that is the basic building block of connective tissues.
Phylogenetics is the classification of organisms based on how closely they are related in terms of evolutionary differences - or in other words the construction of a (phylogenetic) tree structure, a diagram that represent the evolutionary tree of life. A tree of life for the 22 organisms compared in the study is shown in figure 1 of the article. For those of you who do not have access to Science I can refer to this account - NB in Norwegian - of the article, where the figure is shown. Please do note that this tree does not indicate that chicken “descended from the fearsome Tyrannosaurus rex” as mentioned in the heading of Sun here, but merely that Tyrannosaurus, Ostrich (Struthio) and Chicken (Gallus gallus) are related (within the taxon Archosauria). I have redrawn the Archosauria bit from the figure.
A serious problem with using molecular methods, be it on DNA or collagen, is that the samples are extremely easily contaminated (from other organisms, including living species). Furthermore fossil material is destroyed by the analysis, and the analysis is expensive. Of course nondestructive examination of unique fossils are preferred if possible.
Molecular palaeontology in the modern sense probably began with a report by Abelson in 1956 of the recovery of proteinaceous components of fossils. As technology expanded and increased in accuracy, sensitivity, and reliability, new analytical methods began to be applied to fossil material. A piece on the future of molecular paleontology by Mary Highby Schweitzer is found here.
• http://www.livescience.com//animals/080424-dino-birds.html
• http://www.msnbc.msn.com/id/24297066/
• http://www.eurekalert.org/pub_releases/2008-04/hu-mac041808.php
• http://www.thesun.co.uk/sol/homepage/news/article1087903.ece
• http://palaeo-electronica.org/2002_2/editor/r_and_p.htm
There is not much meat on the article itself, it is just one single page, so it may be no surprise, that the media add lots of feathers. Never the less I found the article quite interesting because of the method used to confirm the relationship between dinosaurs and birds.
Evidence of close evolutionary relationships among birds and non-avian dinosaurs have been accumulating for a long time. See a.o. my post on the Archaeopteryx - probably the most famous fossil, and considered an important link between dinosaurs and birds.
In 2005 it became known that a group of dinosaur researchers had discovered soft tissues in fossil Tyrannosaurus rex bone unearthed in 2003 by Jack Horner in the Hell Creek Formation in Montana, USA. As the bone was 68 million years old it is surprising to have found still elastic soft tissues looking like blood vessels and cells. We are not talking Jurassic park and no DNA could be analysed. By using mass spectrometry protein sequenced from collagen were however detected. Collagen is a protein that is the basic building block of connective tissues.
Phylogenetics is the classification of organisms based on how closely they are related in terms of evolutionary differences - or in other words the construction of a (phylogenetic) tree structure, a diagram that represent the evolutionary tree of life. A tree of life for the 22 organisms compared in the study is shown in figure 1 of the article. For those of you who do not have access to Science I can refer to this account - NB in Norwegian - of the article, where the figure is shown. Please do note that this tree does not indicate that chicken “descended from the fearsome Tyrannosaurus rex” as mentioned in the heading of Sun here, but merely that Tyrannosaurus, Ostrich (Struthio) and Chicken (Gallus gallus) are related (within the taxon Archosauria). I have redrawn the Archosauria bit from the figure.A serious problem with using molecular methods, be it on DNA or collagen, is that the samples are extremely easily contaminated (from other organisms, including living species). Furthermore fossil material is destroyed by the analysis, and the analysis is expensive. Of course nondestructive examination of unique fossils are preferred if possible.
Molecular palaeontology in the modern sense probably began with a report by Abelson in 1956 of the recovery of proteinaceous components of fossils. As technology expanded and increased in accuracy, sensitivity, and reliability, new analytical methods began to be applied to fossil material. A piece on the future of molecular paleontology by Mary Highby Schweitzer is found here.
• http://www.livescience.com//animals/080424-dino-birds.html
• http://www.msnbc.msn.com/id/24297066/
• http://www.eurekalert.org/pub_releases/2008-04/hu-mac041808.php
• http://www.thesun.co.uk/sol/homepage/news/article1087903.ece
• http://palaeo-electronica.org/2002_2/editor/r_and_p.htm
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