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Re: More concerning the Triceratops/Torosaurus deal

Let's start with the important part:

 (you might sense that I'm very fond of _Triceratops_...)

Have no fear. *Triceratops* has priority over *Torosaurus* should the two be synonymized.

 how many "species"(taxa?) are expected to be found
 within a "family"(taxon?) pertaining to the same clade?

This is a meaningless question, because "family" is not defined at all, "species" has (as of February 2009) 147 different definitions that often produce different outcomes (for example, depending on the definition, there are from 101 to 249 endemic bird species in Mexico!), and "clade" just means "an ancestor and all of its descendants".

You seem to be asking how many different but closely related species we should expect to find in the same ecosystem at the same time. This is difficult to answer with any precision as long as we don't understand that ecosystem in detail...

 Why is it that _Torosaurus_ has to be _Triceratops_ adlut
 stage? Ontogeny is a nice thing. But what if this was based on
 incomplete fossil preservation, like _Toro_ would be a parent clade
 (?above genus level) of _Triceratops_ , and only subadult stages of
 the latter had been found? Given the quite fast evolution of
 ceratopids during the Cretaceous, is it impossible to think that this
 "_Toro_ adult" stage of _Triceratops_ is actually a subadult stage of
 an adult  _Triceratops_ yet to be found? And, by the same way, that
 young or subadlut _Toro_ have not yet been found?

This is of course entirely possible in principle -- but it is quite improbable in practice, because enormous numbers (hundreds?) of *Triceratops* (apparently none of them adult) and smaller but non-negligible numbers of *Torosaurus* (apparently all of them adult) have been found in the last 120 years from Alberta and Saskatchewan to Texas.