Re: Protopenguins and pterosaurs

[David Marjanovic <david.marjanovic@gmx.at>]

> Nick Pharris nailed the flaw. IF you assert first that penguins and
> storks diverged at 62 Ma, OF COURSE you end with the
> conclusion that there were Cretaceous penguins,

No, to the contrary: if you assert that penguins and storks diverged 62 Ma 
ago, you are asserting that no penguins existed before that time.

All divergence date estimates were run twice, once with an upper constraint 
(in this case again 62 Ma ago) and once without. (Well... four times: with 
and without the 3rd codon positions taken into account.) The dates don't 
change much.

> and other neornithine lineages.

*Vegavis* is not going to go away. It means that at least one lineage of 
Neoaves existed in the late Maastrichtian.

> And that gets you into all sorts of wild speculation. For example, I
> didn't know until I read their paper that the decline of small
> pterosaurs in the late Cretaceous was because they were eaten by
> raptors (and I don't mean velociraptors, I mean Falconiformes!!!).

They do offer the latter "possibility" but, wisely, don't even mention a 
possible connection to the supposed pterosaur decline.

What I find more troubling is their literal reading of the fossil record. 
They don't even take ghost lineages into account, let alone calculate any 
confidence intervals (it's quite hard work, but it's feasible -- my advisor 
and I have done it for an upcoming paper). For all we know, the apparent 
absence of small pterosaurs in the Late Cretaceous could be entirely due to 
the lack of Konservatlagerstätten. The same holds for the "decline" of 
"archaic birds".

This just for fun:
"Models for potential interactions between modern birds, archaic birds, and 
pterosaurs require life history information. For example, early pterosaurs 
show both slow bone growth and year classes (Bennett 1996), thus they may 
have been K-selected. Early birds, such as enantiornithines, show comparable 
patterns, with bone having distinct lines of arrested growth (Chinsamy et 
al. 1998). In contrast, *Hesperornis* and *Ichthyornis*, like neornithines, 
had rapid and sustained bone growth (Chinsamy et al. 1998), suggesting that 
later bird clades were physiologically advanced over earlier lineages."

Did they just mix up K and r, or what's up?

On a wall in Paris VI, near the office of Armand de Ricqlès (one of the many 
coauthors), there's a poster like what is presented on congresses. This 
looks like it's safe for me to publicly mention what it says: an 
enantiornithean from Las Hoyas grew fast when it was young. The only 
difference to extant birds seems to be that instead of stopping completely, 
growth just slowed down drastically, resulting in LAGs in the outer regions 
of the bone... while the inner, older parts got remodeled and are thus 
usually not available for study.

> No matter that we don't have a single
> Cretaceous falconiform in the fossil record.

Their molecular tree predicts Cretaceous falconiforms. That is... there are 
only 25 sequenced genomes of extant birds; in their morphological tree, 
Strigiformes is inside Falconiformes, while there's no owl in the molecular 
tree. Who knows what else might be in that clade that must have originated 
in the K.

> From another post:

> The more liberal estimate, which would actually imply the existence of
> more pre-K/T neorithines than above, is to assume that the 62 mya
> marker is the date of the first node WITHIN Sphenisciformes (ie. the
> split between Waimanu and all other penguins).

Not feasible. *Waimanu* is not in the molecular tree. But see above on lower 
and upper bounds of calibration "points".