[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
New Archaeopteryx paper
Senter and Robins, 2003. Taxonomic status of the specimens of Archaeopteryx.
Journal of Vertebrate Paleontology. Vol. 23, No. 4, pp. 961-965.
The authors used regression analysis to determine if proportional
differences in Archaeopteryx could be explained by allometry. Unlike
earlier studies, they excluded Wellnhoferia (which they support as being
distinct) and included A. bavarica (Munich). The results showed almost all
ratios (tail, scapula, humerus, radius, ulna, metacarpal II, manual phalanx
II-2, ilium, pubis, tibia and pedal digit III compared to femur; hindlimb
compared to humerus; ulna compared to humerus) were explainable through
allometry, although ischiofemoral ratios differed significantly. The latter
have not been used to distinguish putative Archaeopteryx species though.
Senter and Robins make an excellent case for sinking A. bavarica into A.
lithographica, as it was originally distinguished by- larger tibiofemoral
ratio; longer hindlimb-humeral ratio; sternum ossified (Wellnhofer, 1993).
The first two proportions fall into the expected allometric curve, while
it's likely other Archaeopteryx specimens lost their sterna prior to
(London, Maxberg, Berlin) or after (Haarlem) burial. Incidentally,
Elzanowski (2002) reports on sternal fragments preserved in the London and
The authors also bring doubt to Elzanowski's (2002) recent division of
Archaeopteryx lithographica into A. lithographica (London) and A. seimensii
(Berlin). They note (pers. examination by Senter) that all specimens have
pedal flexor tubercles and claim the presence of a m. cuppedicus fossa and
preacetabular ventral process in the large London specimen could easily be
ontogenetic (as processes and muscle attachments are usually better defined
in larger/older individuals). Also, they note the two smallest specimens
(Eichstatt, Munich) have been distinguished by their more recurved and
compressed teeth, which is ontogenetic based on comparison to coelophysids
and tyrannosaurids. The only feature Elzanowski (2002) uses that Senter and
Robins missed was the tall neural spines on cervicals 3 and 4 in A.
bavarica. I see no appreciable difference between it and the Eichstatt
specimen in this regard.
Thus, I agree with Senter and Robins that the Berlin (A. seimensii),
Maxberg, Haarlem (A. crassipes), Eichstatt (A. recurva) and Munich (A.
bavarica) specimens are all conspecific with the London specimen (A.
lithographica). An undescribed eighth specimen also exists (Mauser, 1997),
which is from a lower stratigraphic level than A. lithographica and
Wellnhoferia. Perhaps it will prove distinct once described.