Re: Waimanu & avian evolution (comments)

[Tim Williams <twilliams_alpha@hotmail.com>]

Jim Cunningham wrote:

> Re individual species of late, large pterosaurs going extinct and making 
> room for birds to evolve into their niche, the niche would likely have been 
> filled by another species of large pterosaur long before a bird could 
> evolve into it -- the niches mostly involved marine soaring, so were a 
> small step for another pterosaur, but a giant leap for a small, non-soaring 
> bird.

As a possible counterweight to this last argument, the earliest known 
neornithine birds that show a morphology consistent with marine soaring are 
members of the Odontopterygiformes ("pseudo-toothed" or "bony-toothed" 
birds), which are a very old group.  They had long narrow wings, and are 
thought to have snatched prey from the water surface using their "toothed" 
beaks.  (These teeth aren't real, but were just tooth-like projections.)

Based on new specimens, Bourdon (2005) allies the Odontopterygiformes with 
the Anseriformes (ducks, geese, swans, screamers).  In fact, her 
phylogenetic analysis finds the Odontopterygiformes and Anseriformes as 
sister taxa within a new clade (Odontoanserae), near the base of the 
Neognathae.

Since we have crown-group anseriforms (_Vegavis_) in the Late Cretaceous, 
this implies that odontopterygiforms were around in the Late Cretaceous too 
(they are certainly present in the Paleocene).  If Cretaceous 
odontopterygiforms were albatross-style marine soarers, as proposed for 
Cenozoic odontopterygiforms, then pterosaurs may have had some competition 
in the late Mesozoic.  Or else, the odontopterygiforms originally held a 
different niche (perhaps they were wading birds, like many anseriforms), and 
only filled the marine soarer niche in the Paleocene, after the extinction 
of pterosaurs.

Cheers

Tim