[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: the tonight show
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.
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 <firstname.lastname@example.org>
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:email@example.com
Get your FREE download of MSN Explorer at http://explorer.msn.com