>  >
>>  Just beware that one genus he erected last year is by any criteria an
>>  outright synonym of Zygochlamys...
>
>Dear Andrew,
>
>Please explain.
>
>
>Cheers,
>
>Marien
>
>M. J. Faber
>www.mollus.nl

Pardon me, it was not Dijkstra whom I was thinking of at all! It was
Jonkers! Sorry, Henk!

Jonkers (2003) "Late Cenozoic-Recent Pectinidae (Mollusca: Bivalvia)
of the Sothern Ocean and neighbouring regions", in Monographs of
Marine Mollusca, No. 5, 125 pp., Backhuys Publishers, Leiden. He
establishes the genus Psychrochlamys there for the Pliocene-Recent
species included in Zygochlamys, but I emphatically do NOT agree that
this genus is needed. What Jonkers makes no attempt to explain is,
where did "Psychrochlamys" come from? There is no possible origin
other than the extremely similar South American fossils he includes
in Zygochlamys, so in my opinion he has merely subdivided one genus.
The only significant generic character is the reduction of the byssal
notch and development of a wider (more equidimensional) shell in
adults, rather than remaining chlamydoid throughout life as in
Zygochlamys (although even this doesn't hold - at least one of his
Chilean species included in Zygochlamys is a LOT wider than any
Psychrochlamys species) but this is merely an evolutionary change
with time to adopt a free-living lifestyle. So it changed with time;
why should that make it a different genus?

Off Dunedin, NZ occurs a scallop which I think is the "South
American" species "Chlamys" natans Philippi, which Bert Jonkers
(formerly at BAS) is recording from New Zealand on the basis of one
LARGE fossil (dredged, i.e., a young fossil) from the Campbell
Plateau. Bert is naming a new genus for it, too. [Austrochlamys, as I
recall]. I think they are LGM specimens still lying around on the
shelf. I myself dredged a large fragment of one of these years ago in
500m of water... relicts.

--
Andrew Grebneff
Dunedin, New Zealand
64 (3) 473-8863
<[log in to unmask]>
Fossil preparator
Seashell, Macintosh & VW/Toyota van nut
________________________________
I want your sinistral gastropods!
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Opinions in this e-mail are my own, not those of my institution
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A: Because it reverses the logical flow of conversation.
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