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Re: Marsupials see colors



On 3/27/06, Guy Leahy <xrciseguy@sbcglobal.net> wrote:
> This is interesting... This would appear to knock more
> holed in the hypothesis that black and white vision is
> predominant in mammals because they started out as
> nocturnal animals in order to avoid competition with
> dinosaurs (who were hypothesized to be primarily
> diurnal, although that might not be true, either.)

It looks like only one marsupial species has been investigated:
_Sminthopsis crassicaudata_, the Fat-Tailed Dunnart. Isn't it also
possible that trichromacy is a synapomorphy of some metatherian
subclade that includes _S. crassicaudata_? After all, trichromacy
evolved at least twice among placentals (platyrrhine and catarrhine
simians).

> The apparent ability to see in the UV spectrum is
> interesting... Any thoughts as to what advantage this
> might serve?

No idea; and _S. crassicaudata_ is small and nocturnal, so it seems
like a decent enough ecological model for the ancestral mammals.
Clearly its form of trichromacy is useful to small, nocturnal
mammals--what if that is the ancestral therian condition, and
placentals lost UV trichromacy?

How many mammals have been investigated, anyway? I find it surprising
that this is the first marsupial to be investigated.

Very interesting!
--
Mike Keesey
The Dinosauricon: http://dino.lm.com
Parry & Carney: http://parryandcarney.com