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Re: Latest K dinosaurian diversity trends



> ----- Original Message ----
>
> From: "Harris, Jerald" <jharris@dixie.edu>
>
> DF
>>>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.
>
> JH
>  >   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.
>
> Yes, I'm not sure I have the words as to how to put this properly. Maybe
> this
> works: There is less morphological diversity among late Maastrichtian
> dinosaurs
> compared to Late Campanian dinosaurs.

I think the word you are looking for here is "disparity". Diversity is
technically a measure of the number of taxonomic units (e.g., species);
disparity is a measure of how different from each other those units are.

There is a vast field of literature of comparison between diversity and
disparity; however, a large fraction of it requires one to (**gasp shriek
scream shudder**) look at the marine invertebrate paleontological
literature.