Gao et al. (2012) provide an excellent description of DNHM-D3078, a new Sapeornis specimen. While the illustrations and photos are of high quality and I agree with their main conclusion all "sapeornithids" are synonymous, I'm calling the authors out on two issues.
First, I agree Sapeornis angustis, Didactylornis and Shenshiornis are synonymous with Sapeornis chaoyangensis because it's MY idea. Gao et al. took it without acknowledgement.
Compare my blog post from August 2010 to their discussion of Shenshiornis-
"Likewise, the differences between Shenshiornis primita and S. chaoyangensis proposed by Hu et al. (2010) are either mistaken or questionable in light of the holotype’s preservation (LPM B00018). We do not observe the proposed differences in the length of either the prenarial portion of the premaxilla or the maxillary process of the premaxilla (compare with Zhou and Zhang, 2003:fig. 3), the morphology of the teeth (Fig. 3), the number of sacral vertebrae (compare with Zhou and Zhang, 2003:fig. 4), or the length of metatarsals I and V (approximately 25% the length of the metatarsus; contra Hu et al., 2010); in all these respects, the morphology of these characters is the same as in specimens assigned to S. chaoyangensis. Additionally, the degree of tapering of the anterior margin of the ilium of the holotype of S. primita does not differ significantly from that of specimens of S. chaoyangensis. This margin is not preserved in the holotype of S. chaoyangensis and was incorrectly reconstructed as broad and rounded by Zhou and Zhang (2002, 2003). Our examination of other specimens of S. chaoyangensis (e.g., DNHMD1197, DNHM-D2523) indicates that the anterior margin of the ilium of this taxon is thinner and more tapering than that figured by Zhou and Zhang (2002, 2003) and, presumably, the reference used for comparisons by Hu et al. (2010). Furthermore, the caudal series of the holotype of S. primita is so poorly preserved that the alleged presence of 10 free caudal vertebrae cannot be verified. Morphologically, the holotype of S. primita cannot be discriminated from the holotype (or referred specimens) of S. chaoyangensis; the only significant difference between these two specimens is that the former is approximately 28% smaller than the latter."
Or my entry discussing Sapeornis angustiis posted on October 2009 to their discussion of that species-
"Sapeornis angustis was identified as a species different from the larger S. chaoyangensis on the basis of having fewer sacral vertebrae (six instead of the seven described for S. chaoyangensis) and rather subtle quantitative differences (i.e., narrower humeral deltopectoral crest, narrower furcular rami, shorter hypocledium, longer metacarpal I, and shorter pubic symphysis). Nonetheless, considering that the holotype of S. angustis (IVPP V13396) is likely a subadult (as noted by Provini et al., 2009), these differences can be explained as ontogenetic or intraspecific variability. We also interpret other differences to be the result of preservational biases or errors in measurements. For example, the deltopectoral crest of the holotype of S. angustis is comparable to that of the similarly sized DNHM-D3078 in being narrower than that of larger specimens of S. chaoyangensis, and in having a less abrupt distal angle. Such a difference is likely ontogenetic, because juvenile birds tend to have less developed humeral deltopectoral crests (L.M.C., pers. observ.). The proposed narrowness of the furcula is also questionable, because in the holotype of S. angustis this bone is poorly preserved and partially obscured by the right coracoid; therefore, this apparent
difference cannot be ascertained with confidence. In addition, Provini et al. (2009) correctly noted that some sacral vertebrae might be overlapped by the ilium and ischia; therefore, the smaller number of synsacral vertebrae may well be preservational. Perhaps the most striking difference noted by Provini et al. (2009) is the presence of a proportionally longer metacarpal I in S. angustis. However, our observations of the manus of IVPP V13396 indicate that the measurements provided by Provini et al. (2009) are incorrect. Based on our measurements (Table 2), the length of metacarpal I in S. angustis is 25% that of metacarpal II, exactly the same ratio as in the holotype of S. chaoyangensis."
At the same time, I wrote on Didactylornis. Compare with their discussion-
"The differences used to distinguish Didactylornis jii from S. chaoyangensis are not much clearer. This species was diagnosed as having only two manual digits (i.e., a completely reduced digit III), an elongated first phalanx of manual digit I, and four, instead of five, phalanges in pedal digit IV (Yuan, 2008). However, the manus and pes of the holotype (CDPC-02-08-001) are poorly preserved (Yuan, 2008) and it is reasonable to assume that these apparent differences are taphonomic, particularly when considering the minute size of the digit III of sapeornithids, and the fact that the proximal phalanges of the digit IV of the holotype appear partially overlapped with the distal end of the metatarsals and other pedal digits. In fact, if one were to argue that the first phalanx of manual digit I is as long as claimed by Yuan (2008), this bone would leave no space for metacarpal I (see Yuan, 2008:fig. 1); thus, such argument would lead to the rather startling conclusion that CDPC-02-08-001 retains a digit I when its metacarpal has been completely reduced."
Incidentally, Li et al. (2010) also proposed Didactylornis was a probable synonym, but merely stated "these apparent differences may easily result from poor preservation or damage" without going into detail. This was received in May 2010, seven months after my posting, but at least it wasn't a major conclusion of the paper or argued with the same points. Note Gao et al. don't cite Li et al. either (and that the Zhang in each paper are different, so no authors were shared).
Now, I'm aware my writing was not published in a journal, so someone could reply that I have no claim to the idea, since blogs and websites are not "official" literature. Thus Gao, Chiappe, Chinsamy et al. were free to use my idea without attribution. But is that really the standard we want in our field? If a hypothesis and its support are not written in paper peer-reviewed journals, it's up for grabs for anyone else who wants to put it in the latter venue? Here's an idea- what if workers have the professional courtesy to ask the originator of an idea to be a coauthor? Or link to their website. Chiappe used a "pers. obs." in this paper after all, which is even less verifiable. Or a worse but still more ethical idea- just list the person in the acknowledgements for coming up with that idea. Speaking of the acknowledgements, I suppose no one in peer review noticed this? Am I to believe none of the eleven workers responsible for this paper's publication were aware of my writings? My post is the third result on Google for "Sapeornis Shenshiornis" and the second for "Sapeornis Didactylornis", after all. My website and the DML aren't exactly obscure among Mesozoic dinosaur workers.
The second issue I have with Gao et al. is even worse in a way, since here they are ignoring published literature. You know what a discussion of "sapeornithid" taxonomy should include? Omnivoropteryx. Can you guess what genus wasn't even mentioned in this paper? Omnivoropteryx. Gao et al. use Sapeornithidae when Omnivoropterygidae was named four years earlier. What ever happened to the ICZN and priority? Are Gao et al. really immature enough to be spiteful against Czerkas for his terrible ideas and in house journal/book? We know Chiappe and such are aware of Omnivoropteryx. The funny thing is that the latter genus actually helps the synonymy arguments since it shows the same proportional trends. I'll note that the authors of other omnivoropterygids are also guilty of ignoring Omnivoropteryx, and that Provini et al.'s (2009) silence is particularly troubling, as Omnivoropteryx's holotype shares all the supposedly
diagnostic characters of S. angustis where they can be observed (small
size, short forelimb, low deltopectoral crest with unprojected distal edge,
short pubis). If any of you reviewers ever see sapeornithid or Sapeornithidae in a paper, make sure to do the right thing.
References- Czerkas and Ji, 2002. A preliminary report on an omnivorous
volant bird from Northeast China. Feathered Dinosaurs and the Origin of Flight.
The Dinosaur Museum Journal. 1, 127-135.
Provini, Zhou and Zhang, 2009. A new species of the basal bird Sapeornis
from the Early Cretaceous of Liaoning, China. Vertebrata PalAsiatica. 47(3),
Li, Sullivan, Zhou and Zhang, 2010. Basal birds from China: A brief review. Chinese Birds. 1(2), 83-96.
Gao, Chiappe, Zhang, Pomeroy, Shen, Chinsamy and Walsh, 2012. A subadult specimen of the Early Cretaceous bird Sapeornis chaoyangensis and a taxonomic reassessment of sapeornithids. Journal of Vertebrate Paleontology. 32(5), 1103-1112.
Thoughts on this matter.ReplyDelete