Re: Cretaceous taeniodont

["David Marjanovic" <david.marjanovic@gmx.at>]

> > The increased diversity is totally ridiculous compared to anything
> > Cenozoic.

I can repeat this. :-) Well, the seeming herbivore *Schowalteria* and that
big multi change the picture, but otherwise the "increasedly diverse"
mammals all quite similar ecologically.

> The apparent fact that during most of the Cretaceous (NA, at least)
> this size range was absent...

I think the deltatheridian *Atokatheridium*, which was also in this size
range, is Campanian... *Gobiconodon* was Barremian and existed in NA and
Asia...

> and that just before the terminus their diversity spiked may mean a
> great deal!  Which gets to my question: what constitutes a spike?

The question is wrong. First we need to have a _good_ fossil record that can
tell us when big mammals _were absent_. Because _this_ is what we currently
don't know, and what you assume _a priori_ in order to pose your question.

> > In addition, all big Mesozoic mammals that have been mentioned in this
> > thread were carnivores sort of like a weasel or badger -- that's not a
lot
> > of niches.
>
> >From the insectivory insectivores, to the diet of the above (including
small
> mammals, birds, eggs, fruit, grain, and just about everything else)--on
what
> planet does this not represent a significant leap in niche utilization.

Triconodonts and deltatheridians had been carnivores all the time. Grain?
Only the multituberculates.

> > (The one that hasn't been mentioned, *Kollikodon*, is a problem
> > of its own...)
>
> Can you elaborate?

Said to be 1 m in total length; only known from a partial lower jaw; is
either the basalmost monotreme or Mammalia incertae sedis.

> > Late Jurassic multituberculates
> > flood all vertebrate microfaunas, but they seemingly appear out of
> > nowhere.
>
> Presumably, they all won a free pass to exist.

No, to be preserved. There is a Middle Jurassic mammal that is thought by
some to be the ancestor of multis -- it's called *Eleutherodon*, "free
tooth", and that's what it is, a few isolated teeth free of bone. (Others
suspect it's haramiyidan, which means it has nothing to do with multis at
all.)

> Look, all these speciation
> events are conditional.  Just because we are too far away in time and
> knowledge to know what the conditions are, doesn't mean species'
> distribution is random!

Nor is the distribution of fossils random. Nor is the distribution of
fossils equal! But your questions require a more or less equal distribution
of fossils through the strata.