Re: Giant flightless birds

["Matthew Troutman" <m_troutman@hotmail.com>]

><Ratites, of course, still exist (ostrich, emu, cassowaries, rheas, 
>kiwis and, depending on whom you read, the tinamous, which also fly), 
as 
>do the seriemas which are related to the phorusracoids. The nearest 
>relatives of Diatryma are, I believe, uncertain, though relationship to 
>cranes has been postulated.>
>
>Rails or cranes, plus ducks (and therefore geese).

   Are you implying that rails/cranes and ducks constitute a clade? 
Something along those lines has never been really considered and is very 
unlieky.

>The purpose of my query is to gather data on groups of extinct 
>flightless birds to trace phylogeny to living forms and to the 
>dinosaurs. (Flightlessness being an ancestral trait and therefore a 
>semi-good marker for phylogenetic research, in my opinion. Of course, 
>I've said that before.) I'm trying to find out the adaptations of the 
>rest of the body in addition to/or because of the loss of flight. 
>Especially the pelvis.

    Well, let's talk about a flightless bird's pelvis. If 
alvarezosaurids are birds, then they show a unique amount of variation 
in the structure of the pelvis compared to other birds. Patagopteryx is 
convergent on some ratites in the morphology of the pelvis ( pubis and 
ischium are of equal length and are nearly parallel, with a small 
foot-like process on the dital end. One of the strangest trends in 
flightless birds is the convergent morphology of the pelvis. Some 
flightless ratites, anseriformes, gruiformes, galliforms, 
podicipediformes, gaviiformes, and even hesperornithiformes have a 
arrangements of the pelvis where the pubis and ischium are nearly 
horizontal and extend to the distal end of the pygostyle. The pelvis in 
phorusrhacids, however, is not in this arrangement, and it resembles 
more of that of a flighted, volant bird. The arrangement is conservative 
in all lineages of flightless birds ( and I have only scratched the 
surface on the diversity of them ). It should be noted, with *perhaps* 
the exception of Spenisciformes ( penguins ) and the possiblilty of 
aquatic gaviiform ancestors, that most flightless birds evolved in 
parallel of each other and they evolved the structure of their pelvis 
convergently.

MattTroutman


______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com