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Re: Ah ha! That's where therizinosaurs came from



David Marjanovic <david.marjanovic@gmx.at> (in separate posts) wrote:

> You would, just probably a couple of years later. Nowadays, with
> *Microraptor*, *Rahonavis*, *Anchiornis*, *Archaeopteryx* and the
> "suspicious" *Bambiraptor* and *Sinornithosaurus* on the deinonychosaurian
> side of things, the idea that the quill knobs of *Velociraptor* are retained
> from ancestors that engaged in some kind of aerial locomotion is at least as
> parsimonious as the alternative.


Yes, I agree.  Aerial behavior(s) of some sort was most likely
primitive for Paraves  - and may even extend deeper into maniraptoran
evolution.  But powered flight appears to be highly derived within
Avialae.


Contra Dececchi & Larsson (2011), small maniraptorans didn't need to
be highly arboreal in order to climb vegetation, or to be capable of
"trees-down" aerial descents.  Has anyone considered that the reason
why certain non-avialan paravians had gliding adaptations was
*because* of their poor arboreal abilities?


> Never mind nest robbers. It now seems that the flightless paleognaths became
> flightless in the early Paleocene on the continents as if they were islands
> -- due to the lack of big predators after the K-Pg mass extinction.


Agreed.  And not just palaeognaths.  Several basal neognath lineages
also spawned large, flightless birds at around the same time -
dromornithids, gastornithids (diatrymids), sylviornithids.  This last
one (_Sylviornis_) was found only on New Caledonia, and became extinct
relatively recently.  But like the ratites, dromornithids and
gastornithids, the superficially ratite-like _Sylviornis_ appears to
represent a faily ancient flightless lineage.





Cheers

Tim