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ISOLATED 'ARCHAEOPTERYX' FEATHER.. AGAIN
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
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.
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