The bat-wing bird hypothesis
promoted by Dececchi et al. 2020 and prior authors since 2015 (see below) is a myth. A misinterpretation. A false tradition that will not die. Here I am trying to put yet another nail in a coffin that will not close six years after the first nail.
Perhaps the most embarrassing aspect of this scandal
is the large number of professors, grad students, assorted paleontologists (see below) and paleoartists (see below) who gladly accepted a 2015 reconstruction of Yi qi that not only added a completely new long bone to the arm (the so-called ‘styliform’), but turned a perfectly good Early Cretaceous bird into a bat-wing dinosaur with flight membranes instead of feathers.
was the traditional dictum, “exceptional claims require exceptions evidence”... or in this case, just any meager evidence at all. No one else, using the most advanced imaging techniques (Fig. 1, Dececchi et al. 2020) and first-hand observation, were able to see that poor Yi qi simply suffered from a broken arm.
As an example,
five years after the broken arm had been noted online, Dececchi et al. 2020 were still trying to figure out how Yi qi would have flown with bat-wings and a fourth long arm bone. Highly regarded referees and editors, the traditional gate keepers of good data and good science, kept approving this nonsense in published works (see below).
A closer view:
From the Dececchi et al. 2020 summary:
“The bizarre scansoriopterygid theropods Yi and Ambopteryx had skin stretched
between elongate fingers that form a potential membranous wing.”
Not true. Given firsthand access to the fossil and laser stimulated fluoresence (LSF, Figs. 1, 2) imaging, this team of PhDs was still unable to describe the torsion break in the ulna of Yi qi — even after showing the break itself! Instead, they accepted that this taxon had developed a completely unique long arm bone (the ‘styliform’) while, at the same time, essentially losing a major traditional long arm bone (the ulna) during a taphonomic wing flip of 180º. Funny, odd, embarrassing that the many authors that have so far examined and written about Yi qi never put these facts together, whether by creating a reconstruction or by careful first-hand observation or by using Occam’s razor. It just had a broken arm.
To this day
no one has produced a tetrapod of any kind that has four long robust bones in each forelimb proximal to the manus. Three is the number. It has always been so. Yi qi is no exception. A long pterosaur pteroid is a possible contender, but is always much more slender than the radius and ulna. Pterosaur, bird and bat fingers are not under consideration here because they extend beyond the wrist and are well-accounted for.
Yi qi was nothing more than this:
an ordinary Early Cretaceous bird suffering from a broken ulna and an undeserved reputation.
Question for you, dear reader:
Should Xu et al. 2015 and Deceechi et al. 2020 retract their papers? Like the Oculudentavis scandal, their claims are demonstrably false. Were these examples of headline grabbing by paleontologists who should have know better? Or just a lot of scientists making an honest mistake? As always, decisions like this are up to you, whose opinions ultimately create the consensus.
In theory, facts should override opinions.
However in practice, sometimes (in this case, since 2015) sensational opinions override facts.
Dececchi TA, et al. (8 co-authors) 2020. Aerodynamics show membrane-winged theropods were a poor glidiing dead-end. iScience 2020 https://doi.org/10.1016/j.isci.2020.101574
Wang M, O’Connor JK.; Xu X and Zhou Z 2019. A new Jurassic scansoriopterygid and the loss of membranous wings in theropod dinosaurs. Nature 569: 256–259. doi:10.1038/s41586-019-1137-z
Xu X, Zheng X-T, Sullivan C, Wang X-L, Xing l, Wang Y, Zhang X-M, O’Connor JK, Zhang F-C and Pan Y-H 2015. A bizarre Jurassic maniraptoran theropod with preserved evidence of membranous wings. Nature (advance online publication)
Paleoartist John Conway made an illustration of Yi qi with bat wings you can see here.
Paeloartist Emily Willoughby made an illustration of Yi qi with bat wings you can see here.
Darren Naish blogging for Scientific Americanin 2015 wrote,
“It probably looked more like a bat-winged parrot.”
Darren Naish also reported, “Exactly such a creature was predicted by my colleague Andrea Cau (and illustrated by excellent palaeoartist Lukas Pankarin) way back in October 2008 after the publication of Epidexipteryx* (Zhang et al. 2008).”
Naish continues, “Could Yi qi‘s styliform elements actually be battle spines or something? Xu et al. (2015, supplementary information) state that “we are aware of no case in which a long, unjointed bony or cartilaginous rod extending from a limb joint has evolved in any vertebrate without being associated with an aerodynamic membrane, and plausible alternative functions for such a structure are difficult to conceive”.
“It’s difficult to pinpoint where the mistakes have been made, but my suspicion is that Yi qi would have looked more like other maniraptorans, and less dragony overall.
Seemingly every explanation was offered, but the simplest explanation, the one you can see: a broken ulna.
Naish 2015 continues,
“It shouldn’t be lost on you that Yi qi and other scansoriopterygids look to have been experimenting with flight and climbing, despite being well outside the bird clade itself.”
In the LRT, Yi qi and other scansoriopterygids are birds derived from Solnhhofen birds, members of the bird clade itself.
Some publicity at the time: