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Re: Cretaceous loons
> Is there any credible published information that loons (Gaviidae)
> actually existed in the Cretaceous?
If that's published meanwhile...
www.cmnh.org/fun/dinosaur-archive/2001Jun/msg01056.html also mentions the
species name: *Polarornis gregorii*.
Otherwise: Sankar Chatterjee: The Rise of Birds. 225 Million Years of
Evolution, Johns Hopkins 1997
It's pretty thoroughly illustrated and very convincing. Much more so than
the "parrot" or *Protoavis*.
> Neogaeornis may be a hesperornithiform.
Or not. Some seem to be very sure about this. Anyway it would be the only
southern hesperornithiform, separated from all others by something like
BTW, sorry, it's from Chile, not Argentina.
> Doesn't that just leave Polarornis? Is there anything besides the
> shape of the cnemial crest and skull (both subject to convergence)
Not subject to much convergence because there are several methods for how to
get such a cnemial crest. Three have been realized: using the patella alone,
the tibia alone, or both together. One is seen in hesperornithiforms,
another in podicipediforms, another in loons including *Polarornis*.