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PZ Myers' write-up on new cephalopod paper

tonmo

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#1
A new paper, Cephalopod origin and evolution: A congruent picture emerging from fossils, development and molecules, is written up by PZ Myers on Pharyngula.
 

SteveM

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#2
tonmo;179682 said:
A new paper, Cephalopod origin and evolution: A congruent picture emerging from fossils, development and molecules, is written up by PZ Myers on Pharyngula.
The discussion concerning the persistence of Monoplacophora as the origin of Cephalopoda, and how modern Triblidiida/Monoplacophora might fit in recalls my recent thread concerning pearls attributed to Nautilus.

As recently as 2009, Checa et al at University of Granada determined that the aragonite microstructure of modern Monoplacophora (Triblidiida) was distinct from all other mollusks, naming it Foliated Aragonite. This microstructure has since been reconfirmed in Cambrian mollusks, and is now considered to be the basal shell microstructure from which nacre was derived in the Ordovician.

Thus our current excitement concerning pearls attributed to Nautilus and their foliated aragonite composition (by pure luck, I took them to Checa in Granada for study, who made the shocking discovery last year). Foliated Aragonite has never before been observed in pearls, and certainly has not been observed in modern mollusk shells other than those of Triblidiida/Monoplacophora. Scientifically linking the subject pearls to Nautilus would link Nautilus to extant Monoplacophora, and to their Cambrian originals. But proving pearl species scientifically is a frustrating task, as DNA extraction from shell material thus far remains hypothetical.

Maybe PZ would have some suggestions.
 

hallucigenia

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#3
Has anyone tried working with nacre proteins? I've been planning for some time on doing something like that with ammonoid fossils that have nacre preserved, but it might work for this question too. (And then I ended up working on crinoids instead...such is life.)
 

SteveM

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#4
hallucigenia;180044 said:
Has anyone tried working with nacre proteins? I've been planning for some time on doing something like that with ammonoid fossils that have nacre preserved, but it might work for this question too. (And then I ended up working on crinoids instead...such is life.)
THIS is the most pertinent and recent work (otherwise extra-molecular protein has always been assumed to be unlikely for genomic work), albeit not since duplicated by Dr. Geist or anyone else to my knowledge. Still, it gives hope for future research as techniques improve. But fossilized nacre or other shell organic material would not appear to offer such hope, given the study's determination that the fresher the shell the better.
 

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