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re: Bird-like fossil footprints from the Late Triassic





--- David Marjanovic <david.marjanovic@gmx.at> schrieb am Fr, 31.10.2008:

> Von: David Marjanovic <david.marjanovic@gmx.at>
> Betreff: re: Bird-like fossil footprints from the Late Triassic
> An: dinosaur@usc.edu
> Datum: Freitag, 31. Oktober 2008, 13:12
> > > David, you might be confusing a tibiofibulotarsus
> [...] with the
> > > tarsometatarsus
> 
> Oops! Surprisingly, I did manage to confuse these.
> However...
> 
> > The tarsometarsus can explain the angle. The hallux...
> IONO, not
> > necessarily but it is possible. Also, presence of a
> tarsometatarsus correlates
> > *rather* well with the ability to leave birdlike
> footprints in taxa we know for
> > sure.
> 
> ...I still don't understand that. Theropod and
> ornithopod tracks, not to mention the tracks *Effigia* must
> have made, are surely birdlike enough; why should fusion of
> the already closely appressed, mutually immobile, elongated
> metatarsals lead to a wider angle between the toes?

To get splayed feet and a fully reversed hallux, you need the toe bases (the 
joint where the basal digital phalanges attach) to be arranged in the shape of 
a "c" (right foot viewed proximal to distal along the leg). This is probably 
easier to achieve when there is metatarsal fusion.

Whereas unfused metatarsi would seem to arrange the toe bases in an approximate 
"^" or oblique line.

I observe that widely splayed toes are something of an anomaly in bipeds, and 
like a reverted hallux they correlate nicely with metatarsal fusion.

And I have not seen any study that falsifies the hypothesis that this 
correlation is more than coincidence. But I think there ought to be such a 
study.

That is all I can say: we don't know yet, but there are grounds to assume that 
it would be very fruitful to find out.


Regards,

Eike