Nick Longrich wrote:
I doubt that an excellent sense of smell necessarily correlates
with scavenging as Horner implies (but hasn't to my knowledge demonstrated),
but the question then becomes: OK, well, what DOES a good sense of smell
correlate with, if anything? Clearly, tyrannosaurids were doing something that
dromaeosaurids, troodontids, and ornithomimids were not; I suspect those
gargantuan olfactory bulbs didn't appear for no reason at all... I used to be
sort of skeptical of the contention that the development was that spectacular
in a tyrannosaurid, or figured it might be a scaling thing, but I've seen a
small tyrannosaur frontal (comparable in size to Saurornitholestes,
Dromaeosaurus, Troodon, and ornithomimid frontals) at the RTMP and the
impression for the olfactory bulb suggests something several times as large in
terms of volume as in the other theropods. So did they track prey? Use it for
nocturnal attacks? (i'm sort of partial to the idea of nocturnal tyrannosaurs-
hunting at night might help explain how on earth a T. rex could get within a
half mile of a duckbill without getting seen).
Nick L.
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I think it's reasonable to assume that, as
in all animals with well developed smell senses, being able to detect a
possible mate or potentially "aggressive" members of the same gender was
important in tyrannosaurids; I don't know what are the population densities
suspected for big theropods ( i imagine it would depend on a lot of
things: enviroment,preys density, metabolism etc..), but in case they (the
tyrannosaurs) turned out to have been relatively "rare" (low n° of
individuals/ territory are ratios), the importance of having a good sense
of smell should be considered relevant. I mean , being able to "detect" a
very distant male/female (depending on who looked for who[m]..) would
have been essential as well as being able to recognize the extension (or
at least the edges) of another male's(or female's) territory before getting
dangerously close to the owner.
This is true for all animals, ok, but the chances
of getting killed or badly injured after meeting a 4 tonned "fellow"
tyrant would have been quite a lot.
Behavioral mechanisms considered to have been
selected as a consequence of the fact that avoiding the possibility
of being killed in a male-to-male confrontation(or female-to-female) is
surely a good thing, have been noted, if I'm not mistaken. Ritual
confrontations seem a good example(perhaps the only one?).
In this case, being able to detect a
older,bigger,tougher male/female's territory (or even the same animal) before
entering it (or meeting the "owner") would have been a highly selected
ability, wouldn't have it?
Even only the ability to estimate the degree of
maturity of another animal just by its smell(while keeping far away)
would be (and actually is, in extant animals, isn't it?)
useful;
mature female--->"ok!"
older(probably tougher)individual of the
same gender------>"no way" and so on.
(I'm not trying to anthropomorfize tyrants'
behaviour..just semplifying ).
Anyway, just a couple of thoughts(sorry if
already discussed in the same terms).
Filippo Calzolari
ps: it may probably be of some utility, to
test the testability(sorry..:) of this "hypotesis", to know something about
the dimensions of the same olfactory structures in other big theropods
such as the various charcarodontosaurini , if they turned out to have behaved
similarly to tyrants....now, the problem is that there's not a well-defined
idea of how the latter behaved, right?