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Re: DROMORNITHIDS, GASTORNITHIDS & DUCKS



> Gotta check this one out. Thanks for the ref. Hmmm, first carnivorous
roos,
> then meat-loving "ducks." What's gonna be the next Aussie surprise. Killer
> koalas?

They already HAVE killer koalas =8-) . Thylacoleonidae is considered the
sister group of the koalas!!! (The last "marsupial lion", *Thylacoleo
carnifex*, which died out after humans came to Australia, is thought to have
been the most specialised carnivorous mammal ever.)

> >BTW, *Gastornis* ( = "*Diatryma*") is now also considered to have been
> >carnivorous -- the skull is seriously overdesigned for herbivory, and yet
it
> >is more gracile than that of *Bullockornis* aka "The Bird from Hell" aka
> >"The Demon Duck of Doom".
>
> But as recently as a mid-90's Natural History special issue about
> dinosaurs, diatrymids were considered to have been herbivores. That
article
> compared them to the New Zealand takahe in terms of beak morphology.

1. More recently (but still several years ago), someone found out
gastornithids had skulls that were seriously overbuilt for herbivory. A
takahe beak looks much more gracile _in comparison_.
2. There were big mammalian herbivores around at the time (how big was
*Uintatherium*? Rhino size?), but no carnivores of that size.
3. Takahes have big, strong beaks compared to most birds (but not
gastornithids, dromornithids and phorusracids) because they eat very tough
plants -- grass. There wasn't much grass in the Eocene.
4. Moas were plant eaters, we know that from their stomach contents. They
had tiny heads. So have emus, cassowaries, ostriches, rheas, hens,
ornithomimosaurs (more or less) and sauropodomorphs. All these are either
herbivores and/or eat prey that is smaller than their heads, and they don't
chew, so they don't need big heads (respectively past tense). Now
gastornithids, phorusracids, dromornithids, birds of prey and big nonavian
theropods have large heads because they attack prey that is much larger than
their heads. This is the analogy that Stephen Wroe uses, and I find it very
compelling.

> And if
> I'm not mistaken, *Diatryma* was said to have been built for less speed (a
> waddler, again (?) like the takahe) than say the phororhascids.

While I can't comment about whether *Gastornis* (the senior synonym of
*Diatryma*) waddled (I think not), speed wouldn't have been of much use,
since open grasslands weren't yet "invented"! Practically all land was
covered with forests, most of them tropical and "paratropical" rainforests,
in the Eocene. In the Miocene, from when most phorusracids are known AFAIK,
there were already pampas much like today.