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Re: number of species of dinos



>Peter Dodson originally made the estimate that there were no
>more than 25 species of dinos alive at any one time.
>
>If anyone wants the reference I will look it up and post it.
>
>A simple check on the prossibility of this number being in
>the right ball park comes from another doctrine -- that any
>one species of dinos lasts  only for about 5 million years.
>Given a total time span (the wh ole of the Mesozoic) of  185
>million years, then the total number of dinos should come out
>to 185 divided by 5 (millions of years) times 25 (species
>at any one ti me) equals 925 total species in all.  If (as
>I suggested) the real number is more like 100 species at any
>one time, then the total number of speciess should be about
>3,700.
>
>How many species were there in toto?  Anybody?
>


I think that the differnce between how many species of dinosaur we know
about (or will ever know about) and how many species there actually were
must not be forgotten. I have seen various papers estimating dino diversity
by various means but I seriously question the assumptions made to arrive at
these estimates.

As for your back of the envelope calculation to check the previous
estimate; think about the assumptions you are making;

That the average lifespan of a dino species was 5 million years.
That dinosaurs were around for the whole Mesozoic.
That total diversity remained roughly constant at 25 species.

And this all equals what? An approximation that can not be checked against
any reliable measure.

I am waiting for people to shoot me to pieces on this one but, given the
nature of the fossil record, how han we ever predict with ant conviction
what true diversity was from the fossil record?

Cheers, Paul

pwillis@ozemail.com.au