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Re: bats



BTW... nomina ex dissertationibus. Ablative plural and the Sinowatz 
Principle. :-)

Original Message by Stephan Pickering
Wednesday, 25 December 2002 01:41

> One: I
> think it likely, on the basis of available molecular
> data when viewed through the prism of cladistic
> analyses of chiropteran phylogeny, that bats (perhaps
> not as agile and swift as the Cenozoic forms, but
> still bats) arose before the end-Cretaceous.

As I cited, this depends on the methods including the chosen calibration 
point.

Peter J. Waddell, Hirohisa Kishino, Rissa Ota: A Phylogenetic Foundation for 
Comparative Mammalian Genomics, Genome Informatics 12, 141 -- 154 (2001)
http://www.jsbi.org/journal/GIW01/GIW01F15.pdf

-- and swoop, the divergence Chiroptera -- Fereuungulata can have happened as 
late as 59 Ma.

> Not all
> pterosaurs were extinct by the end of the Cretaceous,
> and so, two: this means sympatric overlapping of
> population dynamics.

However... there isn't much interaction between bats and albatrosses or bats 
and storks, is there any?

> There is, admittedly, no evidentiary basis for my
> supposition, just the "hunch" that the earliest,
> well-preserved chiropterans are quite advanced in
> morphology, and this is only a "short" 10 million
> years, or so, after the extinction events.

Who knows how long it took... I don't see a reason to suppose 10 Ma or more 
should have been necessary, especially if the Danian world was as empty as 
suggested by the impact scenario and the absence (so far...) of a diverse 
fossil fauna from that time.

> Moreover,
> again without fossil evidence to strengthen my
> paradigm, I suspect that not all pterosaurs died at
> the end of the Cretaceous, just as non-feathered
> dinosaurs may have survived into the Cenozoic
> (isolated populations, e.g., hanging on, as it were,
> but their gene pools so damaged and depleted that
> extinction happened)

...presumably within tens, not millions of years.

> But the pterosaurs disappeared
> as well. Why?

"Why not?" is IMHO a more useful question, considering the apparent severity 
of the mass extinction.

> In other words: toward the end of the
> Cretaceous, bats appeared, survived with the feathered
> dinosaurs, some clades surviving, some dying out.

I'd go so far as to assume that a more parsimonious idea is: the whole 
diversification of Laurasiatheria happened after the K-T -- because this way 
fewer lineages needed to survive it. But of course this is putting the cart 
before the horse, using a (well-founded) hypothesis to infer what a lack of 
fossils means.

> I think the feathered dinosaurs survived until now

Most didn't. Likewise true if you wrote "birds". Sorry, can't resist.

> Mammalian
> predation killed off the secondarily flightless
> Phorushacos in South America probably, ca. 3-4 million
> years ago (perhaps in conjunction with the bollide
> impact in Argentina).

Don't know when *Phorusrhacus* itself lived. But other phorusracids were 
alive in both South and North America much later (North: *Titanis*, South:

> Could it be that chiropterans in the Cenozoic, as it
> were, co-opted pterosaur econiches?

Unknown birds co-opting the niches of unknown pterosaurs...

> Were pterosaurs
> nocturnal as are the vast majority of bats?

Hm. Known ones? The big ones seem to have relied on thermics, and there are 
none at night. Smaller ones... no evidence for echolocation, big but not 
overwhelming eyes... who knows.

> One other thought: Gregory Paul has observed that
> pterosaurs and bats share similarities,but with one
> fundamental difference (as examinations of skulls
> demonstrate): bats are bigger-brained. Coupled with
> being faster, and able to "out-think" pterosaurs,

Ouch. How much correlation there is between relative brain size and... 
anything is poorly known. Are you sure bats don't use their excess to process 
the signals of echolocation?

> it could be that our imaginary end-Cretaceous protobats
> survived into the Cenozoic for the same reasons the
> feathered, flying and secondarily flightless,
> theropods survived.

No evidence so far that any flightless ones did.