[Taxacom] Heterastridium

[Frederick W Schueler]

Taxacombers,

I've recently stumbled across references to Heterastridium, and nothing 
I've found in a casual search explains how a globally-distributed 
basketball-size spherical planktonic life-form should arise and 
disappear in the Upper Triassic without apparent ancestors or 
descendants. Is there any contemporary thought on this that's more 
ecological and/or phylogenetic than simple incredulity?

thanks,

fred.
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             Bishops Mills Natural History Centre
           Frederick W. Schueler & Aleta Karstad
        RR#2 Bishops Mills, Ontario, Canada K0G 1T0
     on the Smiths Falls Limestone Plain 44* 52'N 75* 42'W
       (613)258-3107 <bckcdb at istar.ca> http://pinicola.ca
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