The following GIF animation
(Fig. 1) includes the plate and counter-plate of the Eichstaett specimen of Archaeopteryx. The counter-plate was flipped and un-distorted in Photoshop to match the plate (slightly different camera angles introduced the original keystoning). Together the elements better present data identified in the specimen, including feathers, a sternum and furcula (fused clavicles).
is difficult to see, even when traced (Fig. 2). It is merely an impression on the counter-plate and was likely better preserved on the lost portion of the plate. Likewise the clavicles and scapula are difficult to trace.
There is a broken forearm on this specimen
and perhaps that led to its demise in life.
For some unknown reason, the skull
of this specimen has been difficult to figure. Paul (2002) showed several variations illustrated by several paleontologists. We looked at those here. All but one of these were illustrated with three fenestrae in the maxillary fossa, as shown here (Fig. 3 from Rauhut 2013). Only Heilmann (1926) illustrated a single antorbital fenestra without a fossa.
- aof – antorbital fenestra
- mf – maxillary fenestra
- pro – premaxillary foramen
I agree with Heilmann (with regard to the Eichstaett specimen)
I identify only palatal elements and the inside of the other side of the skull on that specimen. See if you agree (Fig. 4).
Although the skull appears to have a concave upper jaw matching a convex mandible, this may be a taphonomic aftereffect. There is a crack in the anterior surangular at the point of greatest stress and no sister taxa share this morphology.
I have not seen the specimen first hand, but have relied on photographs to make these identifications. I have championed the use of digitized photographs and Photoshop to glean data from flattened fossils. Here is one more example of their usefulness.
Indeed the Thermopolis and London specimens
do have the antorbital fossa with accessory fenestra illustrated by Rauhut, Paul and others (Fig. 5), but then the Thermopolis specimen nests basal relative to the other two Archaeopteryx specimens (Fig. 6), sharing several easily overlooked traits with the proximal outgroup taxon, Xiaotingia. to the exclusion of the other two Archaeopteryx.
Comparing these three Archaeopteryx specimens
shows they are indeed sister taxa, but also distinct sister taxa. The high Bootstrap numbers indicates that several characters are not shared by these three taxa.
Please use individual specimens as taxa whenever possible. Don’t blindly combine specimens until you are sure they are conspecific. By taking the short cut and blending two distinct taxa you throw away any chance of identifying subtle interrelationship changes. And you’re letting amateurs, like me, make discoveries that should be yours to make.
Heilmann G 1926. The origin of birds. HFG Witherby, London.
Paul G 2002. Dinosaurs of the Air: The Evolution and Loss of Flight in Dinosaurs and Birds. Johns Hopkins University Press, Baltimore. 406 pp.
Rauhut OWM 2013. New observations on the skull of Archaeopteryx. Paläontologische Zeitschrift 88(2)211-221.