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Re: Tarbosaurus?

George wrote:

>Your comments are derogatory, ignorant, and intolerable.

>No, the first thing that one should investigate is the possibility of 
>behavioral or other factors that would influence the ratio of subadults to 
>adults living in a particular depositional locality.
        Yes, investigate... but you cannot just assume that this signal will
overrid taphonomic biases! You, the man who argues that birds were around
for millions of years without a fossil record, should be more sensitive to
this sort of issue.

>The principal variable 
>that governs the ratio of fossilized subadults to adults at a locality has to 
>be the ratio of subadults to adults in the original population.
        Do you realize how complex an issue this is? In many, if not most,
vertebrate populations, juvenile mortality is much higher than adult
mortality. Thus, the ratio of juveniles to adults in the population may have
very little to do with the ratio of juvenile corpses to adult corpses. Of
course, clutch size is also a very very important, and currently unknown,
variable influencing both of these ratios. Among some birds of prey, such as
the hooded [sic?] eagle, there may only be one juvenile raised at a time,
which would certainly limit the number of dead juveniles, since the parents
can concentrate a great deal of effort on protecting their singular progeny.
Also, factors such as where juveniles vs. adults are likely to die may
greatly influence whether or not they enter the fossil record.
        I know it seems like that ratio should be the stongest signal, and
it might be too, except that taphonomi and preservational factors are at
work on BOTH sides of the formula, modifying the adult representation as
well as the juvenile. The result is a rather chaotic situation. You
certainly cannot just jump to the conclusion that one influence overwhelms
all others. At least, not without evidence. Got some?

>If you'd like to prove me wrong, I'd be most interested in reading the results
>of your field trips to Mongolia and Montana.
        Sometimes you don't have to do the work to know what needs to be
done. In fact, that's why people go to grad. school, to know what they are
getting into. Alan is a veteran of digs in the Dockum of West Texas, the
Late K of Big Bend, and the Pennsylvanian of Oklahoma. He is a fully
qualified geologist working on his PhD at a very respectable university. He
is one of the smartest, hardest working, most critical, and careful
scientists I know. He has actually conducted practical experiments in
taphonomy, and has incorporated taphonomic field observations into his work.
I'd take his skepticism VERY seriously if I were you.

     Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
  "Why do I sense we've picked up another pathetic lifeform?" - Obi-Wan Kenobi