[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

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

But consider this hypothesis. That ratites retain the features of the 
flightless animals that evolved into flying birds. None of the skull features 
that you cited has any bearing on flight or flightlessness. No parallelism is 
required at all.

I understand that, earlier in the last century, some ornithologists held out 
this possibility. Indeed, it has been recently suggested once again (Newman, 
Thermogenesis, muscle hyperplasia, and the origin of birds. Bioessays 33: 
653-656. 2011).

You and I know that the fossil record overwhelmingly falsifies this hypothesis.

But please note my point - there is nothing in ratite morphology that is an 
unambiguous feature correlated with flight. Moreover, no feature, nota  
carinate sternum (found also in alvarezsaurs), not a furcula (found in all 
theropods), not a pygostyle (found also in oviraptorosaurs), nothing, is a 
skeletal feature that is found only in flying birds and not in non - flying 
theropods. Thus it is not possible, purely from anatomical analysis, to 
demonstrate that ratites had flying ancestors. That can only be supported by 
phylogenetic methods.

On Aug 15, 2011, at 9:21 AM, <GSP1954@aol.com> wrote:

> Ratites have a fullt developed suite of derived avian characters, including 
> a skull with a severely reduced maxilla, paleognathus palate, advanced 
> braincase, strut like jugal and so on. Unless a fantastic level of 
> parallalism 
> occurred it is abjectly impossible for them to not have descended from fliers 
> closely related to tinamous. 
> GSPaul
> In a message dated 8/14/11 10:01:56 PM, jaseb@amnh.org writes:
> << What about ratites? How do we know they had flying ancestors?
> My point is that ratites do not retain any single anatomical feature that
> is found only in flying birds. I realized last week that, if we look at
> the anatomy only, ratites could retain the anatomy of an avialan lineage
> that diverged right before flight was attained. I was surprised when I
> realized that. >>
> </HTML>

Jason Brougham
Senior Principal Preparator
American Museum of Natural History
(212) 496 3544