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Dromornithids, the other white meat (was Re: The duck that ruled the world).
João Simões Lopes Filho wrote:
How can be seen the evolution of Diatryma and Dromornithids from
Presbyornis-like birds? From fish-eaters becoming increasingly more
carnivorous until evolving to giant meat-eaters?
Perhaps _Diatryma_ and dromornithids evolved (independently) from a basal
"galloanseromorph" (the chicken + duck group). Such an ancestral form may
actually have been terrestrial and not eaten fish. But this is rampant
speculation - I don't think there's any evidence that either _Diatryma_ or
dromornithids evolved from a _Presbyornis_-like bird. There is good
evidence that _Presbyornis_ is not some basal neognath, but actually quite
derived (especially for the early Tertiary) and very closely related to
modern ducks (Anatidae).
And about that Cretaceous French giant bird Gargantuavis? What was it?
Buffetaut and Le Loeuff (1998) believe the material (a poorly preserved
synsacrum and femur) is too poor to evaluate _Gargantuavis_?s relationships
too closely. They did point out several _Diatryma_-like features though:
the very anteriorly placed acetabulum (positioned under the third and fourth
transverse processes) and the relatively broad pelvis (in _Gargantuavis_,
around 150mm wide compared to 180mm long). Both could be correlated with
flightlessness - though most other flightless birds (hesperornithiforms,
phorusrhacids, modern ratites) have proportionately narrow pelves. The
relatively broad pelvis and forwardly-placed acetabulum of _Gargantuavis_
are also seen in _Patagopteryx_.
_Gargantauvis_ is best regarded as Aves _incertae sedis_.
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