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Re: pterosaurs, bats, flying theropods



Original Message by Stephan Pickering
Friday, 20 December 2002 18:57

> AN EMENDATION: no Cretaceous bats are known, but this
> does not mean their ancestors were not already
> beginning to diversity. Absence of discoveries does
> not mean absence of taxa.

May I, irony of ironies, suggest the following paper

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

which presents a well-resolved molecular tree of Placentalia along with 4 
sets of divergence dates based on 4 different calibration points. If you 
calibrate the tree with the tarsier-anthropoid split ~ 55 Ma ago, then the 
basal divergence of Scrotifera (Chiroptera -- Fereuungulata) happened no more 
than 59 Ma ago, and the basal divergence of Laurasiatheria (Eulipotyphla -- 
Scrotifera) 63 Ma ago. If you take the rabbit-pika split, which is not so 
well known from fossils but taken in this paper to have been 42 Ma ago, then 
you arrive at 61 and 65 Ma ago. Foolish would I be to consider it proof. But 
I do consider it evidence, especially in the absence of evidence that points 
in the other direction. BTW, the oldest remains of *Icaronycteris* may be 
Late Paleocene, filling the gap between this molecular date and the early 
Eocene date for the oldest certain bats.

> > bats (who are NOT flying primates,

HP Jaime Headden asked who ever suggested this. Well. Morphologists have long 
assumed a grouping called Archonta, which contained Primates, Scandentia, 
Dermoptera, Chiroptera and in later versions Lagomorpha and sometimes 
Macroscelidia. Several times Dermo- and Chiroptera were found to be 
sistergroups, forming Volitantia, which (no surprise for Dermoptera) used to 
be the sister group of Primates. And then there is the older suggestion of 
chiropteran diphyly, with megabats alone being (the sistergroup of) primates. 
The debate was considerable and waged for years.

> > but my feeling is that, during the end
> > Cretaceous, when the flying dinosaurs out-competed,
> > as it were, the pterosaurs,

Why do you think this happened?

BTW, Ichthyornithidae survived to the end, as shown by the new big bird from 
the Maastricht Fm.

A bat with slotted wings? ~:-|

> > echolocating abilities of the bats surpassed any
> > such
> > propensities among the theropods who relied on
> > brains and vision (to simplify the picture).

On the other hand, it is damn expensive. The drag alone (from big ears and 
big noses) is enormous. And of course the brain is involved here, too.

> > And the complex
> > ecological web of insects + dinosaurs + pterosaurs +
> > bats

+ fish + who knows what else.

> > fast-slow dynamical systems.

Could you explain what that is, or would it take too long?

> > Dinosaurs, as Greg Paul notes,
> > during the Cenozoic to date, are surprisingly
> > diverse in morphology, whereas bats are not.

Hm. If you subtract flightless and soaring birds, then I'm not so sure. Too 
bad there's no method I can think of for how to measure morphological 
diversity.

> > But, without
> > stepping on scholarly toes, I suggest that bats just
> > might give some light on ecomorphologies of the
> > cluttered skies at the end of the Cretaceous: flight
> > adaptations, vision, vocal/chemical signals, etc.

Light? Possibilites to speculate. Hardly to make testable hypotheses which 
can be discussed further than "yeah, maybe, maybe not" or "42".

> > And,
> > this new book edited by Kunz/Fenton just might
> > provide us with further extrapolation tools.

But we don't know if the line is straight, parabolic, hyperbolic, 
exponential, logarithmic or anything.