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Re: Phorusrhacids killing large mammals in National Geographic Channel



On Mon, Aug 10, 2009 at 01:37:48PM -0500, Raptorial Talon scripsit:
> > It's generally a bad habit to get more than one step of implication away
> > from a nice, solid fact, even so.
> 
> For a science-minded person in a formal setting, or a setting where
> one could easily be misinterpreted or taken out of context, I agree.
> Otherwise, I don't think there's much harm in casual banter between
> educated individuals. ; )
> 
> Specificity and clarity about *when* one is speculating, and to what
> degree, is just generally useful though. That I do habitually.

[snip]
> > The North Amercian list is longer than either the India or Africa list
> > -- short faced bears, grizzly bears, polar bears, black bears; three
> > species of wolves ("buffalo" wolves, timber wolves, coyotes); lions,
> > cheetah, puma, jaguar; this may -- though I do not know how to go about
> > proving this -- be correlated with scale and scope of migrations, which
> > are substantially unimpeded north/south in NorAm.
> 
> Well, I dunno if I'd count polar bears, since I'm pretty sure they
> didn't/don't really coexist with most of the rest

They don't (much) now, though wolves, arctic foxes, and brown bears
interact with polar bears in modern faunal assemblages.  During the
mammoth steppe period, though, when the polar bears must have been
living in a different way than they now do -- I don't believe that
anyone's suggested that, as a species, polar bears are only as old as
post-continental-glaciation pack ice -- they would have interacted with
at least some parts of that list.  There are even a few wild examples of
polar bear/brown bear hybrids.

>, and I think I'd class coyotes on the jackal side of the spectrum
>instead of with wolves, but yeah, it's an impressive list. Especially
>when *Smilodon* and *Homotherium* are factored in, too.

Coyotes are in a pretty seamless genetic continuum with wolves.

>  . . . Shouldn't the "buffalo" wolf be a subspecies? My understanding
> is that Eastern wolves are genetically closer to red wolves, and so
> it's they who would appear to be a distinct species (*C. lycaon*). And
> of course there would have been *C. dirus* as well.

So far as can be told from the extant examples, wolves have either a
great deal of regional variation in one very plastic species, or the
various species are all quite young.  The big ones displace the little
ones in an environment with large ungulate prey; the little ones spread
due to human extirpation of the big ones.  But there is no strong
evidence that they're all distinct species and good evidence -- lots of
interbreeding -- that they're not.

> If we're talking about relatively recent ecosystems, we should
> probably also be including *Meganteron*, *Homotherium*,
> *Pachycrocuta*, Eurasian jaguars, and maybe even *Dinofelis* and
> *Agriotherium* in the discussion of Old World predator guilds - not to
> mention *Chasmaporthetes* across Africa and the Holarctic.

I'm not sure all of that stack are all going to be in the same ecosystem
at the same time, but yeah, it's not a short list.

> Stupid Holocene extinction.

Clovis people gotta eat!

> > Of course, this also raises the question of how you got T. rex and only
> > T. rex in what looks like a herbivore-diverse migratory environment.
>
> Its awesome was too overwhelming.

This is an annoyingly plausible hypothesis.

My own preferred hypothesis is that it was a good deal more social from
a younger age, and did an ontogenetic niche progression.

> More seriously, what truth is there in the idea that Hell Creek
> represents an impoverished, somewhat cooler environment with a larger
> number of individuals in a smaller number of species? Could it be a
> post-turnover ecosystem in which a few weedy species have yet to
> diversify?

Hell Creek might, but I don't know.

-- Graydon