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Re: PhyloCode Discussion: Crowns, Panstems, and their Correspondence to each oth
Jaime Headden wrote:
However, birds such as moa and elephant birds and dodos still belong to
the crown ratites or columbiforms/columbids, so this is not really that
much of a problem.
Actually, whether or not moas (Dinornithithidae+Anomalopterygidae) or
elephant birds (Aepyornithidae) are crown ratites hinges on their position
relative to extant ratites. It is not a 'given'. True, the molecular
(mitochondrial) phylogeny of Cooper et al. (2001) put rheas (Rheidae) as the
basal ratite group, and therefore moas and elephant birds are contained
within the crown group. But I doubt if this study is the final word on
ratite phylogeny. If alternative topologies put moas and/or elephant birds
in a basal position relative to extant ratites (kiwis, ostriches, rheas,
emus, cassowaries), then moas and/or elephant birds are no longer in the
crown group. Under this scenario, moas and elephant birds would be excluded
from Ratitae, if this is the crown group.
In this same sense, the extinct sandcoliids within Coliiformes do
not get to be crowns, but are still part of one.
I'm not sure I know what you mean. The crown group Coliiformes comprise
only living mousebirds plus all descendents of the most recent common
ancestor of living mousebirds. All modern coliiforms belong to two genera
(_Colius_+_Urocolius_) in the family Coliidae. Thus the crown-group is
limited to a subset of the family Coliidae (all descendents of the most
recent common ancestor of _Colius_ and _Urocolius_). The fossil taxa
_Selmes_ and Sancoleidae are outside of crown-grou (for phylogeny, see Mayr
and Mourer-Chauvire, 2004; J. Vert. Paleont. 24: 366-372). The extinct taxa
_Selmes_ and Sancoleidae do not get to be included in the crown group, but
would be in the stem clade ("Pancoliiformes").
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