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Re: [dinosaur] Vegaviidae, new clade of diving birds that survived K/T boundary.



David Marjanovic <david.marjanovic@gmx.at> wrote:

> > And as has been pointed out in a few places online, the spelling should be 
> > "Vegavidae" if it's formed from the generic name Vegavis. Apparently, the 
> > spelling here is patterned after Gaviidae (from Gavia) with a double i..
>
> Ve-gaviidae... ha, I completely missed that :-)


When I saw 'Vegaviidae' I wondered if it was an intentional allusion
to Gaviidae - or just an accidental misspelling.  Either way, I would
have preferred that the authors simply spell the name correctly
(Vegavidae).

The phylogenetic analysis bumps _Vegavis_ out of crown Anseriformes
(Clarke et al. 2005 doi:10.1038/nature03150).  Here _Vegavis_ is a
stem-anseriform, along with a posse of fellow foot-propelled divers
assigned to the Vegaviidae (_Polarornis_, _Neogaeornis_,
_Australornis_).  If vegaviids are stem-anseriforms, AFAIK this means
that there is no compelling evidence for crown Anseriformes in the
Cretaceous.  (The anseriform affinities of _Teviornis_ from the
Maastrichtian, originally described as a presbyornithid, have been
disputed [e.g., Clarke & Norell 2004
doi.org/10.1206/0003-0082(2004)447<0001:NARAAR>2.0.CO;2].)

Agnolin &c included some other extinct galloanserans in their
phylogenetic analysis, such as _Presbyornis_ (confirmed as a crown
anseriform), and _Sylviornis_ and _Megavitiornis_ (both confirmed as
stem-galliforms).  However, they omitted an array of other fossil
galloanserans (or putative galloanserans): dromornithids, _Diatryma_,
_Brontornis_, pelagornithids.

One notable thing is the preponderance of extinct flightless taxa
among extinct Galloanserae.  There's the large terrestrial forms
(dromornithids, gastornithids, brontornithids, sylviornithids), and
likely at least some vegaviids (especially _Neogaeornis_).  This
suggests multiple independent losses of flight among stem-anseriforms
and stem-galliforms, more so if the Sylviornithidae (_Sylviornis_,
_Megavitiornis_) is paraphyletic, as recovered by Agnolin &c.
Galloanserae is uncannily similar to Palaeognathae in the evolution of
multiple lineages of large flightless birds.