Monday, May 11, 2009

On the collagen sequence of the Campanian hadrosaurs (duck-billed dinosaur) B. Canadensis

Collagen sequences from an 80 million year old dinosaur were published recently. 

Schweitzer et al., 2009, Biomolecular Characterization and Protein Sequences of the Campanian Hadrosaur B. Canadensis, Science, 5927, pp. 626 - 631

Below I analyzed the 8 peptide sequences reported.  My analysis showed that B. Canadensis is an outgroup to a T.rex-bird clade, consistent with morphological data but different from the conclusion of Schweitzer et al.  Also, the analysis confirmed the major findings of my early fossil sequence paper.   



100% identical to mouse




100% T. rex, 100% chicken, and 100% mammals, 17/17, 100% mammut




100% T. rex, 100% chicken, 100% rana. 18/18, 17/18 homo, 17/18 mammut




100% Chicken, 17/18 rana, 17/18 homo, 16/18 mus, 13/18 match in mammut,




100% T. rex, 100% chicken, 100% frog/newt/rana, 17/18 homo, 17/18 mammut




100% Chicken, 100% rat, and 100% opossum. 14/15 mus, 13/15 homo, 12/15 mammut




Collagen a2(1)

100% Chicken, and 17/18 Taeniopygia guttata, 15/18, homo, 13/18 mammut




Collagen a2(1)

17/18 T. rex, 17/18 chicken, 16/18, Taeniopygia, 17/18 between chicken and Taeniopygia.  Much less to others.  18/18 between chicken and T. rex. 


Some questions:


1.  Is B. canadensis more related to T. rex than chicken is? 

No.  It is equidistant to chicken and T. rex.  And chicken is closer to T. rex than Bc is to T. rex.  The informative peptide in this case is #8.  Of 4 peptides whose sequences are known in Bc, Tr, and chicken, three (peptide #2, #3, #5) are non informative as they are identical among the three species.


2.  Is B. canadensis more related to birds than to other animals? 

Yes, informative peptides 4, 7, 8 show B. canadensis more similar to chicken than to frog or mammals or any other. 


3.  Is B. canadensis more related to bird than T. rex is?

The only informative peptide is #8.  For this peptide, Tr is 18/18 to chicken and 17/18 to Tg (Taeniopygia guttata).  Bc is 17/18 to chicken, and 16/18 to Taeniopygia.  So, Tr is more related to birds than Bc is.


4.  Is B. canadensis more distant to the outgroup frog than bird/mammal are?

Not a single informative peptide.   Seven of the 8 peptides are not unique to Bc.  Peptide 8 is unique but not very conserved in extant animals.


5.  Is the distance between B. canadensis and mammut greater than that between extant birds and extant mammals?

Yes.  Of 6 informative peptides (1-6 of collagen A1t1), 4 and 6 show that distance between Bc and mammut (25/33) is greater than that between birds and mammals (29/33).  The distance between extant birds and mammut is also greater than between extant birds and extant mammals.  This result confirms the previous finding on the distance between Tr and mammuts. Only the MGD but not the molecular clock hypothesis can predict such result.

Conclusion: Bc is the outgroup to a Tr-bird clade

Schweitzer et al stated: “However, on the basis of well-established morphological analyses (25), we predict that T. rex is more closely related to birds than it is to the ornithischian hadrosaur B. canadensis.” 25. D. Pisani et al., Proc. R. Soc. London Ser. B Biol. Sci. 269, 915 (2002).

Yet their molecular analysis based on certain statistical methods suggest that the two dinosaurs belong to a clade to the exclusion of birds.  Such a conclusion is false because it is based on the completely mistaken paradigm of molecular clock and neutral theory.  So, my analysis shows Bc as the outgroup to a clade containing birds and Tr.  This conclusion is more consistent with morphological analysis.  The fact that Tr is closer to a bird Gg than a bird Gg is to another bird Tg may be due to the fact that Tr has 60 million years less time to mutate than extant birds are, or that Tg had a different dinosaur ancestor.  

1 comment:

John M Asara said...

Dear Huang-jin Shi-zi,
Could you please post a pictorial view of the phylogenetic tree based on your MGD analyses that includes B. canadensis, T. rex and Mammut?
Thank you,