First, Tim Williams already noted this on the DML, but Wang et al.'s phylogenetic definition of Confuciusornithidae as "The most-inclusive clade that contains Eoconfuciusornis zhengi Zhang et al., 2008, but not Sapeornis chaoyangensis Zhou & Zhang, 2002, or Passer domesticus Linnaeus, 1758" is wrong in not including Confuciusornis sanctus. I don't know why it's so hard to use eponymous taxa...
This was erected by Hou (1997), but we both agree it's just a Confuciusornis sanctus. There are a few characters Hou mentions as distinctive (ten free caudals, slightly developed olecranal fossa, radial groove and patella) but are not in his diagnosis, so go unmentioned by Wang et al.. But based on Hou's inaccuracy in other areas, I maintain these are probably misinterpretations.
Also named by Hou (1997), this is just based on a hindlimb. Wang et al. provide good photos and interestingly find the specimen is a left leg instead of a right one. While Chiappe et al. thought the lack of proximal tarsal fusion was equivocal, Wang et al. view it as genuine and ontogenetic. I said "Finally, Hou lists "metatarsal V is present and is isolated, except for its articulated proximal end", but it is present in C. sanctus as well. The discussion indicates it is metatarsal V's robusticity and lack of fusion with the tarsometatarsus that Hou belives is unique. Examination of photos leads me to believe that what's identified as metatarsal V is actually a broken proximal end of metatarsal II. This would explain why the metatarsus is so narrow, and why metatarsals I and V are on the same side." Wang et al. confirm this with "Furthermore, the element identified as metatarsal V by Hou (1997) is in fact the incomplete metatarsal II, as indicated by its medial position and robust size." We both agree it's indeterminate within confuciusornithids.
|Holotype of Confuciusornis chuonzhous (IVPP V10919) as illustrated in Hou (1997) (left) and Wang et al. (2018) (right).|
Regarding only known specimens (holotype and paratype), Wang et al. report "unfortunately, neither of these specimens can be located at this time." This is yet another example of IVPP specimens being lost and is rather concerning. I wrote "(proposed) narrow, tapered and vertical ascending process of maxilla" as a diagnostic character, and Wang et al. agree and write "we identify two new cranial features diagnostic of C. dui: the dorsal process of the maxilla rapidly tapers dorsally, forming a triangular shape in lateral view." Of course, Elzanowski et al.'s (2018) recent paper shows that we were all wrong about the maxilla in Confuciusornis and that it actually has a low internal ascending process and no external ascending process. Their other supposedly new cranial feature is "the ventral margin of the surangular is straight in C. dui lacking the ventral process seen in C. sanctus and E. zhengi", but this was actually listed in its original description ("without the distinctive anteroventral expansion of the dentary found in C. sanctus") and is a plesiomorphy anyway.
The authors interestingly report some Confuciusornis specimens have a posteriorly grooved furcula like Changchengornis. They also interpret the supposed maxillary fenestra more correctly than Chiappe et al. (1999) as being within the lacrimal, although missing Elzanowski et al.'s idea that the lacrimal and ethmoid complex are fused. Finally, they include "tarsometatarsus without plantar excavation" in the diagnosis despite that being plesiomorphic compared to Confuciusornis (sanctus, at least).
This is a very useful section of the paper, since both species of the genus were described in Chinese and only Chiappe et al. (2008) have examined their validity in print, albeit briefly. Regarding J. yixianensis, I wrote "Characters like "braincase small" and "second manual digit not particularly expanded" appear to differ at first glance, but I have a feeling examination of the specimen would show otherwise" and indeed Wang et al. provide excellent photos showing the skull is exposed in lateroventral view and that manual phalanx II-1 is not exposed (covered by manual ungual I and sediment if present). Supposedly different in having more than 12 dorsal vertebrae, I said "Confuciusornis may have had over twelve dorsal vertebrae" but it seems the answer's actually the opposite and that the posterior dorsals of J. yixianensis are missing so that it can't be shown to have twelve dorsals in the first place. For J. zhangjiyingia, Chiappe et al. (2008) stated the supposed quadratojugal-orbit contact cannot be confirmed, and Wang et al. show that this portion of the 'quadratojugal' is actually part of the postorbital. Indeed, one of the weird findings of Elzanowski et al. is that the quadratojugal of confuciusornithids has yet to be identified, and that laterally exposed bone in that area of the skull could easily be non-homologous elements as in some recent birds. In any case, the authors agree with Chiappe et al. and I that Jinzhouornis is a junior synonym of Confuciusornis sanctus.
I proposed Eoconfuciusornis zhengi was closer to Confuciusornis than Changchengornis and potentially closer to Confuciusornis sanctus than C. dui based on characters like the surangular process invading the external mandibular fenestra. I said "The only character which would place zhengi outside Confuciusornis (sanctus + dui) is the absent humeral foramen, but this may be ontogenetic and seems to be developing as a fossa in the specimen", and the authors note referred specimen BMNHC-PH870 (Navalon et al., 2018) has a humeral foramen. BMNHC-PH870 wasn't published when I examined confuciusornithid taxonomy, but would seem to have relevance. Notably Wang et al. didn't defend placing Eoconfuciusornis outside Confuciusornithidae or diagnose the genus Confuciusornis, although it did fall out at the base on Confuciusornithiformes in their tree.
In a rare exception to the norm, I think the authors are correct to synonymize a taxon that I kept separate. Turns out its original describers were wrong in claiming the humeral foramen was absent and that manual phalanx I-1 is subequal in width to III-3. Pending detailed examination of the situation, I agree with Wang et al. that C. feducciai is just a large C. sanctus with longer wings than average.
|Holotype of Confuciusornis jianchangensis (PMOL-AM00114) pelvis in right lateral view as illustrated by Li et al. (2010) (top), photographed by Wang et al. (2016) (middle) and interpreted here (bottom).|
Continuing the exceptions, I might have been wrong not to synonymize this species with C. sanctus. I've so far agreed with Cau's (2010) blogpost that found this species to share some characters with Ornithothoraces. However, Wang et al. provide better photos that show the ornithuromorph-style ischium illustrated by Li et al. (2010) isn't there. Instead, there is a large proximodorsal process like Confuciusornis and enantiornithines, and the distal ischium is missing so we can't tell if a mid-dorsal process was present or what the ischiopubic ratio was. While Li et al. provided a short fibular measurement suggesting complete and reduced fibulae, the right fibula definitely goes underneath the tibia and the left one might. Wang et al. correctly note metatarsal V is easily lost or hidden, so that it's not necessarily truly absent. The final supposedly different character is the reduced dorsal count, but I can't verify Li et al.'s cervicodorsal transition in the photos. Interestingly, what might be the tip of a scapula projects dorsally from below the pectoral vertebrae, so maybe the forelimb lies under the sediment and could resolve the issue definitively.
References- Hou, 1997. Mesozoic birds of China. Taiwan Provincial Feng Huang Ku Bird Park. Taiwan: Nan Tou, 228 pp.
Chiappe, Ji, Ji and Norell, 1999. Anatomy and systematics of the Confuciusornithidae (Theropoda: Aves) from the Late Mesozoic of Northeastern China. Bulletin of American Museum of Natural History. 242, 1-89.
Chiappe, Marugan-Lobon, Ji and Zhou, 2008. Life history of a basal bird: morphometrics of the Early Cretaceous Confuciusornis. Biology Letters. 4(6), 719-723.
Li, Wang and Hou, 2010. A new species of Confuciusornis from Lower Cretaceous of Jianchang, Liaoning, China. Global Geology. 29(2), 183-187.
Martyniuk, 2012. A Field Guide to Mesozoic Birds and Other Winged Dinosaurs. Vernon, New Jersey. Pan Aves. 189 pp.
Elzanowski, Peters and Mayr, 2018. Cranial morphology of the Early Cretaceous bird Confuciusornis. Journal of Vertebrate Paleontology. 38(2), e1439832.
Navalón, Meng, Marugán-Lobón, Zhang, Wang, Xing, Liu and Chiappe, 2018. Diversity and evolution of the Confuciusornithidae: Evidence from a new 131-million-year-old specimen from the Huajiying Formation in NE China. Journal of Asian Earth Sciences. 152, 12-22.
Wang, O'Connor and Zhou, 2018. A taxonomical revision of the Confuciusornithiformes (Aves: Pygostylia). Vertebrata PalAsiatica. DOI: 10.19615/j.cnki.1000-3118.180530