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Re: New Cretaceous bird and other papers



> Doesn't it feel like you're really *trying* to stretch things out?

I'm definitely arguing on little evidence.

> wonder
> why people who eagerly (and correctly) accept the presence of Middle
> Jurassic dromaeosaurs and troodonts based on teeth are so unwilling to
> accept the presence of modern families of birds in the late K based on
> [...] molecular evidence. Falconiformes were present as fossils in the
> Paleocene. The distance between Liaonang and the Middle Jurassic is like
30
> million years... that's almost half of the entire Cenozoic!

But without a big mass extinction in between, unlike the K-T. Fossils
regularly show enormous radiations after mass extinctions, molecular clocks
_never_. Sort of suspect, no? I obviously can't say Falconiformes MUST be a
part of such a radiation, but IMHO it's quite a parsimonious assumption
(which BTW would also explain why it's so hard to find their sister group).
Falconiformes in the Paleocene is no surprise.
        Also, I'm aware that dinosaur teeth are generally of limited
diagnostic value. We don't know what undiscovered clades had convergently
evolved troodont etc. teeth (or lorisiid beaks). It's just that there are
(comparatively) lots of Jurassic apparent "dromaeosaur" and troodontid
fossils, well-preserved members of both groups directly afterwards,
*Archaeopteryx* which pretty certainly drags them all down to at least the
LJ by its _own_ presence, and no considerable mass extinction in between.

> Why is it then
> so hard to accept the existence of Falconidae or Accipitridae less than 10
> million years before we find their fossils, especially when molecular
> evidence says they should have been there?

Because molecular clocks so frequently contradict known fossils, and because
their error margins are impressive. I mean, 65 -- 83 Ma. Take the lower end
and you almost reach the earliest fossils; take the upper end and
Falconiformes is older than *Apsaravis*.

> >Well, who knows. Let's find a [few] fossils.
>
> Right, like with the parrot which nobody wants to believe, but which
> *everyone* identified as a parrot before Tom Stidham told them how old the
> damn thing was. It has diagnostic characters, just like the troodont teeth
> in the Jurassic do.

It has diagnostic characters of _crown group_ parrots and _lorisiids_. It's
a bit too good to be true. All known Eocene parrots _don't have parrot beaks
at all_. Sure, this alone is no evidence that lorisiids are not that old and
have had a very strange evolutionary history, but assuming it's not a
lorisiid looks on the whole quite parsimonious.
        What is it then? Good question :-) -- well, maybe some otherwise
unknown clade of Pygostylia. Didn't someone mention turtles last time?

> And it's right where the molecular analyses say it
> should be, just like our phylogenetic analyses say there should be
troodonts
> in the Middle Jurassic.

Molecular clock estimates are a different thing than molecular phylogenies.
You compare the former with morphological phylogenies... hm.
        Speaking of phylogeny, parrots are nested _high_ in Neornithes.
Having a lorisiid in the LK drags the other two clades of crown group
parrots, the Eocene parrots, and at least Columbiformes with it -- that's
quite an impressive diversity! I'm interested in what *Piksi* will turn out
to be, and I probably can't discuss the LK presbyornithids of the USA and
Antarctica away. But assuming almost the entire diversity of Neornithes in
the Cretaceous is IMHO a stretch.