ISOLATED 'ARCHAEOPTERYX' FEATHER.. AGAIN

[darren.naish@port.ac.uk]

While sorting through a back-log of newish references the 
other day I happened to read Benton & Gower (2002), a 
biographical appreciation of Alick D. Walker (1925-1999). 
There is one thing in there which might be of particular 
interest to people on this list. 

As is well known, Walker worked on _Archaeopteryx_ 
several times during his career. As Benton & Gower show, 
he later seemed to regret getting involved with the debates 
about this taxon and made efforts to avoid it altogether. In 
part this was due to the (negative) feedback he received 
from an open letter he wrote to colleagues round about 
1995. Benton & Gower write: 'The main thrust of the letter 
was that the isolated feather comprising the holotype of _A. 
lithographica_ was indeed that of modern birds in many 
respects but that it differed in observable structure from 
those of the remaining _Archaeopteryx_ specimens that 
included the skeletal elements. He concluded that these 
skeletal specimens were a different and only distantly 
related taxon to _A. lithographica_.' (p. 4).

I haven't seen this assertion made before in any of Walker's 
writings and would be interested to know what the 
differences Walker observed between the isolated feather 
and those of the feathered skeletons were: does anyone 
know? 

It seems however that he had reached similar conclusions to 
Griffiths (and, IIRC, Ostrom (1970) at least inferred that the 
feather might belong to something else). In his review of the 
isolated feather, Griffiths (1996) writes '... there is no proof 
that the feather came from the same taxa as the skeletal 
specimens, and in view of the differences in the morphology 
and preservation of the isolated feather when compared with 
the other examples, it is a question which deserves some 
consideration' (p. 16). 

He elaborates: 'However, the differences in the morphology 
of the isolated feather, when compared to the morphology 
of the feathers associated with the skeletal examples are not 
so easy to explain. Firstly, the isolated feather appears to be 
smaller. Also, none of the feathers associated with the 
skeletal examples display such a clearly marked clip to the 
tip, they are all much longer than the isolated feather in 
comparison to the width, and none show the same degree of 
asymmetry. Speakman and Thompson (1994) have shown 
that the feather asymmetry ranges from 1.44 for the London 
specimen, to 1.46 for the Berlin specimen where the 
asymmetry can be measured, while the isolated feather has 
an asymmetry of 2.2 at the 25% point. There are problems 
when it comes to accurately analysing the morphology of 
the feathers associated with the skeletal specimens as they 
usually overlap each other, and they are only impressions in 
the matrix so that the distal tips may not be completely 
represented, thus the difference in the proportions between 
the isolated feather and the skeletal specimens may be 
simply due to morphometric scaling. However, the 
alternative explanation that the isolated _Archaeopteryx_ 
feather comes from the different smaller species, perhaps 
_Archaeopteryx bavarica_ or yet another new species 
cannot be excluded' (p. 16).

As Griffiths notes, the differences he points to do not 
demonstrate that the isolated feather does not belong to the 
same taxon as the _Archaeopteryx_ skeletons. And while 
Walker came to similar conclusions, we don't know (yet) on 
which observations these conclusions were based. 

Notably, the implication (either subtle or less so) from 
Walker (in Benton & Gower) and Griffiths is that the name 
_Archaeopteryx lithographica_ is attached to the feather, 
not the London specimen. More recently Bühler & Bock 
(2002) have argued the same. I know this has been 
discussed on the list before, but this issue has been entirely 
sorted, with the London specimen being declared the 
holotype by way of an ICZN ruling. Bühler & Bock 
suggested that the London specimen then be designated the 
neotype, but if (as shown above) there are doubts as to 
whether the isolated feather and the London specimen 
represent the same taxon, then that's a bad decision. Does 
anyone know what the latest news on Bühler & Bock's 
proposal is? (there are supposed to have made an 
application to the ICZN).

Refs - - 

Benton, M. J. & Gower, D. J. 2002. Alick D. Walker 1925-
1999: an appreciation. _Zoological Journal of the Linnean 
Society_ 136, 1-5.

Bühler, P. & Bock, W. J. 2002. Zur Archaeopteryx-
Nomenklatur: Missverständnisse und Lösung. _Journal für 
Ornithologie_ 143, 269 ?286.

Griffiths, P. J. 1996. The isolated _Archaeopteryx_ feather. 
_Archaeopteryx_ 14, 1-26.

Ostrom, J. H. 1970. _Archaeopteryx_: notice of a ?new? 
specimen. _Science_ 170, 537-538.

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

email: darren.naish@port.ac.uk
tel: 023 92846045