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

Re: the tonight show





Ronald,
I was not defending the use of the term "dino-bird", and must admit I winced when I read that.
However, palaeognaths are indeed one of the many cladistic "halfway-houses" between the Neognaths and primitive forms (like Archaeopteryx and dromaeosaurs). Other halfway-houses are the extinct Ichthyornithiformes, and further back the enantiornithines.
Paleognaths are admittedly the closest of the halfway-houses to the Neognaths as a whole, but I think it is unnecessary quibbling to say that they are not an evolutionary halfway-house. And even within Neognathae, one could justify saying a Galliform-Anseriform clade is a halfway house on the way to the sparrow (and other passeriforms). In between these clades, identifying cladistic halfway-houses gets very controversial (much less lining them up in the correct branching order).
A lot of evolution occurred between the first Paleognathae and the first passeriforms (and even more getting to today's sparrow). The paleognaths found their niches, and their evolutionary rates dropped compared to most neognaths. And evolutionary rates are relevant to how "closely" organisms are related.
------Ken
P.S. I would certainly not say a koala is "more like" a crossopterygian than an elephant, but Metatheria is one of the many cladistic halfway-houses between the sarcopterygian Order Coelacanthiformes and the mammalian Order Probosciformes. I'm running late---got to run for now. Have a nice Tuesday everyone!!! :-)
********************************************************
From: Ronald Orenstein <ornstn@home.com>
I must disagree. Calling a cassowary a "dino-bird" will imply to a general audience not that it is marginally more like a Velociraptor than a sparrow is (and I am not sure I buy this either), but that it is some sort of
halfway-house between birds and (other) dinosaurs. Of course it is nothing of the kind. It is a perfectly good modern bird, though a palaeognath. You could just as easily say that a koala is more like a crossopterygian fish than an elephant - hardly a useful statement even if, genetically, it might be (marginally) true.



-- Ronald I. Orenstein Phone: (905) 820-7886 International Wildlife Coalition Fax/Modem: (905) 569-0116 1825 Shady Creek Court Mississauga, Ontario, Canada L5L 3W2 mailto:ornstn@home.com


_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com