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GNETOPHYTES & LEAF WARBLERS



Further to the recent discussion on this list about gnetophytes, I have a 
question.. 

One of Heilmann's most famous drawings is of a group of 
ornithomimids walking around/feeding from a large plant that looks 
something like a _Welwitschia_. Is it a _Welwitschia_ and, if not, 
what is it?

RE: recent discussions on OW warbler systematics, I always thought 
that _Phylloscopus_ was paraphyletic because Pallas' warbler (_P. 
reguloides_) looks an awful lot like an intermediate between leaf 
warblers and kinglets. However, phylogenetic analyses of plumage 
patterns indicate that _Regulus_ is basal and outside of the clade that 
includes _Acrocephalus_, _Phylloscopus_, _Locustella_ and _Cettia_. 
These genera can all be distinguished osteologically - characters 
include tarsal length, size and shape of naris, rostrum and forehead 
shape and shape of pygostyle - but the boundaries are fuzzy.

It's not the genera but the species that are the big problem 
osteologically: now they really are indistinguishable (WRT leaf 
warblers and other passerine species flocks). And don't forget - DNA 
indicates the presence of not one taxon within _Phylloscopus 
sibilatrix_ but 15... cue arguments re: 'frog's eye view'.

DARREN NAISH 
PALAEOBIOLOGY RESEARCH GROUP
School of Earth & Environmental Sciences
UNIVERSITY OF PORTSMOUTH
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