A new paper
by Elzanowski, Peters (no relation) & Mayr 2018 studies the temporal region of Confuciusornis (Early Cretaceous, 125 mya) and other birds. The team writes: “their skull presents a puzzle because it is said to have retained the diapsid temporal region of their avian ancestors (Peters and Ji, 1998; Hou et al., 1999), which is discordant with their phylogenetic position and other cranial features that are much more derived relative to Archaeopteryx.”
Elzanowski et al. make the traditional mistake of assuming all Solnhofen birds are congeneric (= all Archaeopteryx). They are not. Wellnhoferia (formerly Archaeopteryx) grandis (BSP 1999, Fig. 4) is a basal confuciusornithid in the large reptile tree (LRT, 1191 taxa). Therefore, the traits found in Confuciusornis cannot be “much more derived relative to Archaeopteryx”. The team also does not realize the pygostyle evolved several times by convergence (in the LRT).
Based on taxon exclusion
Elzanowski et al. make several phylogenetic assumptions that are not validated in the LRT. They write, “Confuciusornis sanctus has been heralded as a bird with an ancestrally diapsid skull, although this does not match its phylogenetic position as determined by other skeletal features.” They also seem to have missed several traits in their tracing of the Berlin specimen (Fig. 1).
Figure 1A. Berlin Confuciusornis skull as traced by Elzanowski et al. and colorized here. Note the postorbital is broken during crushing. Hyoids are misidentified. Lacrimal and teeth are overlooked. The vomer and palatine are peeking out from the anterior maxilla. The plesiomorphic diapsid temporal region is present here (contra Elzanowski et al. 2018).
Figure 1B. Confuciusornis Berlin specimen teeth.
The Berlin MBAv1168 specimen
is distinct from the GMV specimen in several ways (Fig. 2). The MBAv1168 specimen is twice as tall, has a longer neck, shorter tail, smaller, wider sacrum, larger unguals and a longer pedal digit 4 among other traits. The Berlin specimen has tiny teeth (overlooked by Elzanowski et al in Fig. 1), like all related taxa except the GMV specimen. In the LRT the MBAv1168 specimen nests with Changchengornis (Fig. 4), not Confuciusornis (due to the presence of teeth and other traits).
Figure 2. The GMV and MBAv specimens to scale. See text for details and differences.
The Berlin specimen is preserved with many feathers,
including the two elongate tail feathers that mark this as a male (Fig. 3).
Figure 3. The Berlin specimen assigned to Confuciusornis sanctus is preserved with a full set of feathers, including two long tail feathers. Surprisingly, the furcula came to rest on top of the neck.
tested here include the taxa in figure 4.
Figure 4. Confuciusornithiformes to scale. Note the lack of a pygostyle in the majority of taxa.
Hundreds of Confuciusornis specimens are known.
Only two have been tested in the LRT. Elzanowski et al. had first hand access to the Berlin specimen and others. I relied on published photographs and color tracings of the elements and creating reconstructions to replace displaced bones to their in vivo positions.
Elzanowski A, Peters DS & Mayr G 2018. Cranial morphology of the Early Cretaceous bird Confuciusornis. Journal of Vertebrate Paleontology Article: e1439832. DOI: 10.1080/02724634.2018.1439832.