[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: New paper on fish fingers



> >> Maybe it is to be expected that new clades with
> major
> >> morphological novelties will arise from
> "bushes" in which there
> >> has been extensive "experimentation."
> 
> My impression is rather that such chaos rules everywhere,
> not just at the origin of arbitrarily selected "major
> morphological novelties". That has to be expected --
> natural selection goes into whatever direction the
> environment determines, and few environments are seriously
> stable.

If dispersal capability is very high, this need not be the case. The 
"experimentation" stage in penguins, flamingos, most charadriiforms (excepting 
larids), anatids, most daedalornithids (excepting hummingbirds), falcomids, ... 
cannot have lasted much more than 10 Ma, and they have a) remained anatomically 
and ecomorphologically rather conservative ansd stereotypical and b) achieved 
such a competitive advantage as to permit few other lineages to muscle into the 
same niche. Procellariiforms are perhaps most extreme case.

Passeriformes, strigiforms and psittaciforms are intermediate cases 
(anatomically very conservative but ecomorphologically very diverse in the 
first, a prolonged "experimentation period" in the other). Ratites are more 
similar to early avialans in this regard. In cypselomorphs, it is just the 
other eway around - the basal lineages are very conservative in all regards, 
while compared with daedalornithids (the most advanced major clade of 
cypselomorphs) is radically divergent.

> Compare any two analyses of the same dinosaur
> clade...

Depends on the clade's age. Anything existing for less than say 5-10 Ma is 
usually fairly stereotypical.


Regards,

Eike