[darren.naish@port.ac.uk: [FOR DML] Columbiforms and parrot origins]

[Mike Taylor <mike@indexdata.com>]

Forwarded on behalf of Darren Naish.  Enjoy.

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From: "Darren Naish" <darren.naish@port.ac.uk>
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Date: Wed, 19 May 2004 09:27:08 +0100
Subject: [FOR DML] Columbiforms and parrot origins
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Hi Mike

Here's that post again. Let's hope it makes it this time...

- -------------------------
Regarding proposals that parrots might be allied to 
columbiforms, there are a few things that haven't been 
mentioned. The idea that parrots might be columbiform 
derivatives was favoured by Mayr & Amadon (1951) and 
has been popularised by Feduccia; he wrote '. shorebird 
derivatives include the sandgrouse, doves, and pigeons
(Columbiformes), and, through the tooth-billed pigeons, the 
parrots (Psittaciformes)' (Feduccia 1980, p. 98) and later 
referred in passing (p. 252 of Feduccia 1996) to parrots as 
'the columbiforms' presumed close allies'. Though the 
inference from Feduccia (1980) is that tooth-billed pigeons 
are ancestral to parrots, the figure caption on p. 99 states 
'The tooth-billed pigeons are probably surviving relicts of a 
group that became specialized after diverging from the main 
stem of columbiform evolution, and they show many 
anatomical features that would be found in the ancestral 
stock of parrots'. This implies convergence between tooth-
billed pigeons and parrots, not direct affinity. The Tooth-
billed pigeon is BTW _Didunculus strigirostris_ from 
Samoa (though known from fossils to have lived on Fiji, 
and with an unnamed species of the genus known from 
Tonga).

While writing these contradictory comments, Feduccia 
probably had in mind Philip Burton's 1974 paper on parrot 
and pigeon jaw and tongue morphology. Burton (1974) 
showed that _Didunculus_ was more like a parrot than was 
any other kind of bird in many details of cranial 
musculature. Burton listed five features seen in 
_Didunculus_ which 'showed some approach to [the 
condition in] parrots' and was also impressed by features 
such as the form of the palatines and quadrates, the fused 
lower jaw (hey, maybe Stidham's jaw is from a didunculine
pigeon..:)), the long pterygoids, the short, deep upper jaw, 
and the broad nasal bars (pp. 272-3). In the conclusions of 
the paper it's therefore no surprise that Burton proposes that 
_Didunculus_ may exhibit shared derived states with 
parrots: Burton cites Cracraft (1972) here so is alluding to 
the idea that these features might be synapomorphies. 
Rather than proposing that _Didunculus_ might be near the 
ancestry of parrots however, Burton chickened out and 
wrote 'More likely _Didunculus_ is a relict survivor of a 
specialized group of pigeons which became separated early 
from the main stock of Columbiformes. This may not be the 
actual group from which parrots evolved, but clearly shows 
many of the anatomical features which might have been 
expected in the stock ancestral to parrots.' (p. 274). 

So while _Didunculus_ was used by Burton as evidence 
supporting a possible link between pigeons and parrots, the 
similarities discovered between _Didunculus_ and parrots 
were regarded by him as convergent, or in other words were 
>dismissed< as evidence for a close affinity. As it happens, 
_Didunculus_ is almost certainly nothing to do with the 
ancestry of parrots, but Burton would have been justified in 
proposing a possible affinity at the time. So: why propose 
an affinity of parrots and pigeons when the 'trump card' (= 
the cranial characters of _Didunculus_) is deemed an 
example of convergence? Yes, why indeed.

Recent work on columbiforms supports the view of 
Goodwin (1967) and others that _Didunculus_ is well 
nested within pigeons and is not a disparate relict or part of 
a group well separated from other pigeons. Janoo (1996) 
wrote that 'despite the morphological skull divergence,
_Didunculus_ is a typical columbine'; molecular studies 
show that _Didunculus_ is part of the same columbid clade 
as _Goura_ (crowned pigeons), _Caloenas_ (Nicobar 
pigeons) and dodos and solitaires (Shapiro et al. 2002); and 
morphological work supports similar affinities but finds 
_Gallicolumba_ to be close to these pigeons too (e.g., 
Goodwin 1967, Worthy 2001, Mahler et al. 2003). The 
bottom line is that, while _Didunculus_ is rather like a 
parrot in aspects of cranial morphology, it represents the 
extreme among a group of robust-skulled frugivorous 
pigeons and is nothing to do with parrot ancestry at all, and 
therefore should not be inferred to be suggestive of a 
pigeon-parrot link.

Refs -

Burton, P. J. K. 1974. Jaw and tongue features in 
Psittaciformes and other orders with special reference to the 
anatomy of the Tooth-billed pigeon (_Didunculus 
strigirostris_). _Journal of Zoology_ 174, 255-276.

Cracraft, J. 1972. The relationships of the higher taxa of 
birds: problems in phylogenetic reasoning. _The Condor_ 
74, 379-392.

Goodwin, D. 1967. _Pigeons and Doves of the World_. 
British Museum (Natural History)

Feduccia, A. 1980. _The Age of Birds_. Harvard University 
Press.

- - . 1996. _The Origin and Evolution of Birds_. Yale 
University Press.

Janoo, A. 1996. On a hitherto undescribed dodo cranium, 
_Raphus cucullatus_ L. (Aves, Columbiformes), with a 
brief taxonomical overview of this extinct flightless 
Mascarene Island bird. _Bulletin du Muséum national 
d'Histoire naturelle, Paris_ 4e série, 18, Section C, no 1, 57-
77.

Mahler, B., Araujo, L. S. & Tubaro, P. L. 2003. Dietary and 
sexual correlates of carotenoid pigment expression in dove 
plumage. _The Condor_ 105, 258-267.

Mayr, E. & Amadon, D. 1951. A classification of recent 
birds. _American Museum Novitates_ 1360, 1-32.

Shapiro, B., Sibthorpe, D., Rambaut, A., Austin, J., Wragg, 
G. M., Bininda-Emonds, O. R. P., Lee, P. L. M. & Cooper, 
A. 2002. Flight of the dodo. _Science_ 295, 1683.

Worthy, T. 2001. A giant flightless pigeon gen. et sp. nov. 
and a new species of _Ducula_ (Aves: Columbidae), from 
Quaternary deposits in Fiji. _Journal of The Royal Society 
of New Zealand_ 31, 763-794.

- -- 
Darren Naish
School of Earth & Environmental Sciences
University of Portsmouth UK, PO1 3QL

http://web.port.ac.uk/departments/sees/staff/NaishD.htm
email: darren.naish@port.ac.uk
tel: 023 92846045

Darren Naish
School of Earth & Environmental Sciences
University of Portsmouth
Burnaby Building
Burnaby Road                           email: 
darren.naish@port.ac.uk
Portsmouth UK                          tel: 023 92846045                   
PO1 3QL                                www.palaeobiology.co.uk
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