Re: seeking clarification on the cladism debate

["T. Mike Keesey" <tmk@dinosauricon.com>]

On Wed, 17 Oct 2001 Dinogeorge@aol.com wrote:

> Well, not quite for nothing. When a species is given its own higher Linnaean
> taxa, this usually indicates that it has a long independent lineage within
> the group it is classified in, something that is often useful to know and not
> entirely obvious if it simply appears in a cladogram or cladistic taxonomy as
> a sister group to all the other clades in the group.

No, not necessarily. It may have had a very short independent lineage, but
it would still have all the same ranks as a very long one.

And in practice, it's often difficult to tell whether something has a long
or short independent lineage. Does _Archaeopteryx_' lineage, separate from
other avians, stretch back to the Triassic (as Chatterjee would have it)
or merely to the early Late Jurassic?

The best way to show lineage length (or the lower bound for it, anyway) is
a cladogram set to time.

> Also, those monospecific higher taxa may in time acquire more occupants.

At which point they may warrant more taxa.

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