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Re: Latest K dinosaurian diversity trends
>you can split the only
North American Late Maastrichtian hadrosaurid (Edmontosaurus) into 3 taxa if
you like, but it's still only the one clade, whereas in the Campanian we had
multiple clades (3-4 hadrosaurines, 3-4 lambeosaurines). So diversity is just
modified by a multiplier depending on whether you are a splitter or not.
This doesn't make any sense. Using this same logic (using clades, rather
than species, to define diversity), one could say that there's only one clade
present in the Late Maastrichtian terrestrial gnathostome fauna: Gnathostomata.
Really low diversity, that. Or among arthropods, one could say that there's
only Hexapoda.
Because phylogenetic systematics jettisoned the Linnean rank system,
there's no longer any way of which I'm aware (real or artificial) to compare
clades of "equivalent" "degree," which appears to be what you're doing here --
you're saying that you can use Hadrosauridae and Ceratopsia as units useful for
measuring diversity, whereas Gnathostomata and Hexapoda aren't. Certainly I
get that you're looking for relatively small units, which is fine, but what
criteria do you use to draw the line between what is a useful unit and what
isn't? Why not Ornithopoda and Marginocephalia? Or Ornithischia and
Saurischia? This is why it matters whether or not various lineages represent
species or genera: each one is a unit that presumes some sort of comparability;
most people would only consider species as "real" (remember that a genus is
just another clade). Is counting Hadrosauridae as a single unit useful if it
contains 6-8 internal units (3-4 hadrosaurines, 3-4 lambeosaurines) as opposed
to Hadrosauridae as containing 100 units? Or 2? That is, does Hadrosauridae
really capture anything useful about diversity in the Late Maastrichtian if you
don't know how many units it contains?
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jerry D. Harris
Director of Paleontology
Dixie State College
Science Building
225 South 700 East
St. George, UT 84770 USA
Phone: (435) 652-7758
Fax: (435) 656-4022
E-mail: jharris@dixie.edu
and dinogami@gmail.com
http://cactus.dixie.edu/jharris/
The way to a man's heart is through
his stomach.
-- old proverb
"The way to a man's heart is through
the fourth and fifth ribs."
-- Katchoo (and others)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jerry D. Harris
Director of Paleontology
Dixie State College
Science Building
225 South 700 East
St. George, UT 84770 USA
Phone: (435) 652-7758
Fax: (435) 656-4022
E-mail: jharris@dixie.edu
and dinogami@gmail.com
http://cactus.dixie.edu/jharris/
The way to a man's heart is through
his stomach.
-- old proverb
"The way to a man's heart is through
the fourth and fifth ribs."
-- Katchoo (and others)