Presbyornis, Diatryma, and dromornithids (was Re: The duck that ruled the world)

["Timothy Williams" <twilliams_alpha@hotmail.com>]

Betty Cunningham wrote:

> How would Diatryma be related to Bullockornis?

Interesting point.  My guess is that they probably weren't closely related, 
since _Diatryma_ (a gastornithid, perhaps even the same as _Gastornis_) like 
brontornithids and phororhacids are usually thought to be related to modern 
Gruiformes (cranes, rails, coots).

I'm guessing there is a publication coming out on _Bullockornis_ and the 
affinities of the Dromornithidae.

While on the topic, can anyone tell me why "_Phorusrhacus_" is now the most 
common spelling for this genus?  When I was a kid I distinctly remember it 
being spelled "_Phororhacus_".

> How would Presbyornis be related to Bullockornis?

Again, probably not closely related.  If _Presbyornis_ was a basal member of 
the Galloanserae (Galliformes+Anseriformes, or landfowl+waterfowl clade), 
and dromornithids evolved from such basal galloanserine stock, then this 
idea might fly.  But...

Two papers published in 1997  poured cold water on the idea that 
_Presbyornis_ is a primitive or basal anseriform (Anseriformes = the 
duck-swan-goose-screamer group).  Livezey (1997) and Ericson (1997), in two 
separate papers in the _Zoological Journal of the Linnaean Society_, both 
favour the idea that presbyornithids are the sister group to the modern 
Anatidae.  This puts _Presbyornis_ phylogenetically closer to the anatids 
(modern ducks, geese and swans) than the anatids are to other extant 
anseriforms (screamers, magpie-goose).  Livezey finds support for a 
Galliformes+Anseriformes clade, but Ericson does not.

I know Olson and Parris (1987), in their paper on New Jersey's Cretaceous 
birds, liked the idea that _Presbyornis_ was some type of missing link 
between the "transitional Charadriiformes" and the Anseriformes.  This idea 
seems dead in the water (no pun intended).

Later (1995), Feduccia implicated these "transitional Charadriiformes" (to 
which most Late Cretaceous neognaths from North America have been referred) 
as important in the origin of all modern avian orders.  This too cannot be 
supported by osteological evidence, and seems to be born entirely from 
Feduccia's "intuitive" notions regarding bird evolution.  The "transitional 
Charadriiformes" are described by Livezey as an "undiagnosed, hypothetical 
group".  He raises the interesting point that many poorly-known Cretaceous 
birds (_Telmatornis_, _Graculavus_, _Cimolopteryx_ etc come to mind) are 
assigned to modern bird orders in the same way that many Mesozoic mammals 
were once referred to the mammalian order Insectivora.  They may not even be 
neornithines.

There's also some skepticism regarding the monophyly of the Charadriiformes, 
but that's another kettle of fish (Charadriiformes = "shorebirds" = auks, 
gulls, plovers etc).

Ahhh.  Time for a beer.


Tim

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