Some Allometric Qualities and Taxonomy in Archaeopteryx

["Jaime A. Headden" <qilongia@yahoo.com>]

I decided to take up the challenge of recent allomerty issues raised for
*Archaeopteryx* species identification and support, so have some comments
to make.

Houck, M.A.; Gauthier, J.; & Strauss, R.E. 1990. Allometric scaling in the
earliest fossil bird, *Archaeopteryx lithographica*. _Science_ 247:
195?198.

Senter, P. and Robins, J.H. 2003. Taxonomic status of the specimens of
*Archaeopteryx*. _Journal of Vertebrate Paleontology_ 23(4): 961-965.

  The main issue was to find a major line of regression, and look for
deviations among it with other specimens, in an attempt to determine if
there was, in fact, a specimen outside of the regression. I made a table
of all ratios of all specimens, and used the length of the humerus and the
femur to calibrate the order from largest to smallest. Nearly all
specimens corresponded along these two scales with the exception of the
"Maxberg"
and "Eighth" specimens, which are in private collections and I did not
measure yet. In this table, size progressed from the Solnhofen specimen,
to to the Lodon, Haarlem (or Teyler), Berlin, Münich (or Solnhofener
Aktien-Verein), to the Eichstätt specimens. According to Senter and
Robins, the "Maxburg" is almost identical in size to the Eichstätt
specimen. 

  The results of the comparisons were not surprising, such as that the
Solnhofen specimen (6th, Solnhofner exemplar, BMM collection,
"*Wellnhoferia grandis*") was the largest along all regressions except for
some ratios of the pedal phalanges, in which these were just shorter than
those in the London specimen (1st, Londoner exemplar, BMNH 37001, holotype
of *A. lithographica,* though von Meyer wanted to call it *Griphosaurus
longicaudatus,* then it was changed to *Griphornis,* when the feather was
at some times considered the holotype). The longest first metacarpal
belongs to the Haarlem, or Teyler specimen (4th, Haarlemer exemplar, TM
6928 and 6929 [part and counterpart], made the holotype of a non pterosaur
species, "*Pterodactylus crassipes,*" also referred to *Scaphognathus* and
*Rhamphorhynchus*), which is third in the series. The Berlin specimen
(2nd, Berliner exemplar, HMN 1880 and 1881 [part and counterpart], the
holotype of *Archaeornis* or *Archaeopteryx siemensii*) is the fourth
largest, but has a longer first phalanx of the second manual finger,
longer than that of the third largest specimen, the Haarlem. The Eichstätt
specimen (5th, Eichstätter exemplar, JM SoS 2257, holotype of "*Jurapteryx
recurva*") is the smallest, but has unguals in the hand larger than in the
Münich specimen (possibly preservational, but claws are complete for those
measured, and the variation is by 3-5mm, so this may account for claw
sheaths) as well as the second phalanx of the fourth toe being longer.
However, most peculiarly, nearly the entire leg of the Münich specimen
(7th, Müchner exemplar, BSP 1999 I 50, the holotype of *Archaeopteryx
bavarica*) is larger than the Berlin specimen, yet the arm, hip and
shoulder are smaller, with the exception of a slightly longer tibia (by
1mm); the variation is as little as 1mm (metatarsal III) to as much as 5mm
(metatarsal IV), but the phalanges are almost always within 3% and 25%
longer, mostly closer to subequal, so this shows only slight, maybe
preservational, variation.

  Aside from the variation in allometry (which is minimal), some specimens
show only variation in small regions, usually confined to the extremities.
I haven't compared vertebral lengths yet, given the resolution of my
sources (varying qualities of photos, this is an amateur post and if I had
access to casts I would use them instead). However, the given material
shows that size is close knit and forms a nearly complete series, and much
of this was likely as old as subadult or older. *Wellnhoferia* appears to
be a divergent adult of *Archaeopteryx,* which skeletal differences
confined to possibly abbreviated chondrification of the tail and
phalanges, so they they failed to segment into an addition pedal phalanx
on the fourth digit, and a more "abbreviated" tail. There have been very
few truly distinct skeletal differences or features cited for support of
some species, the most distinct of which were the Solnhofen specimens
abbreviated tail and toe, and the presence or absence of flexor tubercles
of the foot claws, which in some cases are very, very small (Solnhofen,
Berlin) or large and distinct (London, Eichstätt) that seem to defy the
scaling properties. However, these do not support given taxonomic schemes.
As Senter and Robins indicated, presence or absence of the sternum is
likely an artifact of preservation. Position and morphology of the ischium
has been cited as well, but for the most part, the element is less that 45
degrees off the vertical in most specimens, and the one abberant position,
in the Berlin specimen, would appear to show disarticulation and partial
overlap, as the contacting shapes are at odds with all other specimens
[this could be due to THEIR being wrong, but the preponderence of
specimens would argue otherwise]. The ischial shapes appear to vary due to
preservation, as these are almost always broken to one degree or another,
and missing most of the shaft (Solnhofen), portions of the processes
(London, Münich), or obfuscation (London). Finally, as noted by Senter and
Robins, tooth shape varies with regionalization on the regression, smaller
specimens having more curved teeth than larger specimens.

  Thus, it would appear that *A. bavarica,* *J. recurva,* *A. siemensii,*
and *W. grandis* are likely junior synonyms of *A. lithographica.*

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


        
                
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