[Taxacom] Clade age (was: Taxacom Digest)

Kenneth Kinman kennethkinman at webtv.net
Wed Nov 9 20:36:49 CST 2011

Hi Michael,   
       I was not automatically assuming that the clade age (for
Lamiaceae + Acanthaceae and relatives) was within 5 million years of a
possible fossil age in the Coniacian.  But given the Conacian age of
that fossil pollen of 86-89 million years, and estimates of 95 and 97
million years for a more inclusive clade (crown group Lamiales), that
would make "roughly" 90 million years a very good hypothesis for the
intermediate clade (by common sense "bracketing").  No "default" setting
involved at all.  And even if I had, a 5 million year range (plus or
minus) out of 90 million is not as big a deal as a 5 million year range
(plus or minus) at 17 million years of age.  Mesozoic ages are clearly
less precise than Cenozoic ages, so any "default setting" for the
Miocene would not be appropriate for the Cretaceous (even if I had been
using one).          
P.S.   In any case, if there is no pollen of Lamiaceae in the
Cretaceous, then we would have to go with the pollen in the Eocene of
China (ca. 44 million years ago), which would indicate to me that
Lamiaceae arose far later than 85-89 million years, perhaps even after
the end-Cretaceous event (65 million years ago).  However, in that case,
any hypothetical age (by bracketing) is going to be less precise given
the longer ranges in time.  Anyway, I am mainly interested in
determining whether or not the Conacian pollen belonged to Lamiaceae or
to some other family.  I clearly didn't anticipate getting dragged into
a debate involving Miocene fossils that are much more recent.                                
Michael Heads wrote:
      The modern synthesis relies on the 'default setting' that clade
age = fossil age + ~5 m.y. (e.g. see Ken's last post) and this is being
slipped into the Bayesian work in the assignment of priors. Michael
Wellington, New Zealand. 

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