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Re: Query on so-called "correlated" characters



Would the following characters be considered co-related and therefore
one would be unusable?

1. Height of last sacral neural spine greater than acetabulum
diameter.    Height of first caudal spine greater than centrum height.

Tricky. I would expect a strong correlation between the height of the last sacral neural spine and the first caudal neural spine (though I haven't actually looked into that). The question is: how much correlation is there (in your dataset) between acetabulum diameter and centrum height?


2. Quadratojugal process of jugal present or absent.
Quadratojugal present or absent.

The first must be scored as unknown (which, for PAUP*, is the same as "inapplicable") in all taxa that lack a quadratojugal.


3. Femur absent. Number of tarsal bones zero.

The second must be scored as unknown in all taxa that lack a femur (and thus automatically also the rest of the hindlimb).


Besides, the second character has problems of its own. First, it is correlated to certain kinds of aquatic lifestyle (like axial-based swimming) and therefore most likely correlated to a couple other characters in the matrix. Second, it's correlated to ontogenetic age: for taxa known from adults, score the adults and ignore all other specimens; for taxa not known from adults, score the highest observed number of tarsals _or higher_ (partial uncertainty). Together, these issues might make the character useless -- try to figure that out (I can't do it without your dataset).

4. Naris larger/smaller than antorbital fenestra.    Antorbital
fenestra present or absent.

The first must be scored as unknown in all taxa that lack an antorbital fenestra.


I note that in certain recent papers and reviews this has become an
increasingly sticky subject.

Why? It's straightforward, except for my extra remarks about tarsal ossification.