Archaeopteryx: the scattered skull of the London specimen

Updated November 8, 2015 with cranial data from Alonso 2004 that I just became aware of.

Figure 1. Archaeopteryx London specimen skull. The anterior is more clearly presented and has been previously illustrated. Here I colorized matrix discontinuities that could be posterior skull elements. At least they all fit together in a basic Archaeopteryx-type skull that matches other specimens.

Figure 1. GIF animation of the skull of the London specimen of Archaeopteryx. Perhaps other bones are also present. If so I did not identify them. The bones here are clear, less clear and not very clear. Compare these colors to the colors in the reconstruction and you’ll see a close correspondence to the bones of other specimens.

As far as I know,
prior workers did not identify or illustrate the posterior skull bones of the London specimen of Archaeopteryx (Fig. 1, but see below). Bones left only the faintest of impressions (if correct here), but seem to correspond to the same bones of better known specimens (Fig. 4). Higher resolution images should confirm or refute these tracings.

New data (November 8, 2015)
came in the form of Alonso et al. 2004, which extricated and CT scanned the skull of the London Archaeopteryx. The new illustration in figure 2 reflects that data. Apologies that I was not aware of this at the time of this first posting.

Figure 2. A new paper (Alsonso et al. 2004) on the cranium of this specimen has come to my attention. The cranium was buried in the matrix and these new illustrations reflect the more complete data.

Figure 2. A new paper (Alsonso et al. 2004) on the cranium of this specimen has come to my attention. The cranium was buried in the matrix and these new illustrations reflect the more complete data.

Every bone here
appears to fit and not stray too far from morphologies established by better preserved skulls. As noted earlier, the large number of premaxillary teeth in the London specimen, along with other traits, make it distinct from the Eichstaett specimen (Figs. 3, 4).

While we’re on the subject of basal birds,
here are a few to scale (Figs. 3, 4). It is notable that the more primitive ones are the smaller ones in this selection of taxa.

Figure 4. Enanthiornithine birds to scale. Click to enlarge.

Figure 4. Enanthiornithine birds to scale. Click to enlarge. Evidently there are a few other taxa without a sternum in this clade.

Be sure to click on figure 4 to see it at full size.
The stem birds, Xiaotingia and Eosinopteryx form a short-face clade with their own autapomorphies. Rahonavis nests with Velociraptor, not with birds in the large reptile tree.

Figure 4. Archaeopteryx and a few stem birds to scale compared to a chicken (Gallus). Click to enlarge.

Figure 4. Archaeopteryx and a few stem birds to scale compared to a chicken (Gallus). Click to enlarge.

The convergence of Late Jurassic birds and Late Jurassic pterosaurs
Here it is clear that the reduction of the long tail in birds occurred with phylogenetic miniaturization and neotony. Earlier I demonstrated the same tail reduction in four clades of pterosaurs that ultimately developed ‘pterodactyloid’-grade traits. They each had their genesis in tiny pterosaurs experiencing phylogenetic miniaturization and neotony.

The refusal of pterosaur workers
to recognize that embryo and juvenile pterosaurs match their parents, and that tiny Solnhofen pterosaurs are adults the size of living hummingbirds is the reason why their cladograms fail to demonstrate gradual accumulations of traits in derived taxa. Odd that tiny birds get novel generic names, but tiny pterosaurs do not.

It may be
that only tiny birds survived the end of the Jurassic, just like tiny pterosaurs. Later they both developed into larger forms.

Rahonavis
(Forster et al. 1998) survived into the Latest Cretaceous (Maastrichtian). Not sure whether it stayed small or evolved smaller than other velociraptors. At present it nests basal to that clade.

I still think reconstructions bring necessary data to the table. 
Hope you do too.

References
Alonso PD, Milner AC, Ketcham RA Cookson MJ and Rowe TB 2004. The avian nature of the brain and inner ear of Archaeopteryx. Nature 430:666-669.
Forster CA, Scott D, Chiappe LM, Krause DW. 1998. The Theropod Ancestry of Birds: New Evidence from the Late Cretaceous of Madagascar. Science 279 (5358): 1915–1919.

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