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re: Bird-like fossil footprints from the Late Triassic
> <Why is their tibiofibulotarsus relevant to the angle
> between the digits, and how does the first toe fit?>
> David, you might be confusing a tibiofibulotarsus, which
> is (to my understanding, or at least how it's used in
> birds and mammals) a coossified element, with the
> tarsometatarsus, which excludes the fibula and is also used
> to define the limb segment between knee and ankle, rather
> than a bone complex.
Heterodontosauridae had both.
As it is known that they were widespread throughout Gondwana at the right time,
had the right size range, and at least their "heels" (= midfeet) looked more
like those of Enantiornithes even than those of Euornithes IIRC, it must be
falsified that they made the tracks.
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 mentioned Heterodontosauridae because I went looking for any such study a
year ago or so, and did not find any. Every paper was going wild about "birdies
in the Triassic!" but nobody ever seems to have checked the obvious.