[Taxacom] 53 million year rabbit foot

Ingo Michalak isoran at gmx.de
Mon Nov 21 14:25:22 CST 2011


Dear Jason,

I rather think it is the crown age you can assign the fossil age to (as 
a minimum), and not the stem age. (Why should the "sample" of extant 
spp. somehow have an influence to the placement of the fossil?)

Best


Ingo

schrieb Jason Mate:
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> ´´I agree with you that a well-dated fossil puts a minimum age for the clade. But one has to be careful about assuming any phyletic relationships, for even the oldest members of a clade can exhibit unique specializations, thus likely representing any of a multitude of extinct lineages. Insular forms of Lagomorpha have existed at different times, and islands are a common feature since the break-up of Pangaea.´´
> We agree that we are in agreement but I just want so say that I make no assumptions regarding the fossil. As you have said yourself assigning a fossil (in this case a Lagomorph) to a particular group within the crown clade requires information which may or may not be available. That is why the most inclusive placement is the standard practice. If the fossil represents a Lagormoph sensu amplo then we can only speak for Lagomorpha as a whole and the fossil is a date for the crown node.
> BestJason
>
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