You heard it here first: Others also doubt the theropod affinities of Oculudentavis

The now famous tiny skull in amber, Oculudentavis, 
(Fig. 1; Xing et al. 2020) continues as a topic of conversation following its online publication in Nature and two previous PH posts here and here.

Figure 1. Oculudentavis in amber much enlarged. See figure 2 for actual size.

Figure 1. Oculudentavis in amber much enlarged.

Several workers have also thrown cold water
on the tiny theropod affinities of Oculudentavis. Oddly, all seem to avoid testing or considering in their arguments the sister taxon in the large reptile tree (LRT): Cosesaurus (Fig. 2). Instead, they report on what Oculudentavis is not. Examples follow:

Dr. Andrea Cau writes in TheropodaBlogspot.com Link here (translated from Italian using Google translate): 

“I believe that the interpretation proposed by Xing et al. (2020) is very problematic. Oculudentavis in fact has numerous anomalous characteristics for a bird and even for a dinosaur. And this makes me doubt that it is classifiable within Dinosauria (and Avialae).

  1. Absence of anti-orbital window. [not true, click here]
  2. Quadrate with large lateral concavity. This character is not typical of dinosaurs, but of lepidosaurs. [that quadrate is twisted, the other is not, the concavity is posterior in vivo]
  3. The maxillary and posterior teeth of the maxilla extend widely below the orbit.
  4. Dentition with pleurodont or acrodont implant.
  5. Very large post-temporal fenestra.
  6. Spoon-shaped sclerotic plates is typical of many scaled lepidosaurs.
  7. Coronoid process that describes a posterodorsal concavity of the jaw reminds more of a lepidosaur than a maniraptor.
  8. Very small size comparable to those of the skulls of many small squamata found in Burmese amber.

“In conclusion, there are too many “lizard” characters in Oculudentavis not to raise the suspicion that this fossil is not a bird at all, let alone a dinosaur, but another type of diapsid, perhaps a scaled lepidosaur, if not possibly a specimen very immature than some other Mesozoic group (for example, a Choristodere). It is well known that many types of reptiles present in the final stage of embryonic development and in the very first moments after hatching a cranial morphology similar to the general one of birds (of in fact, the bird skull is a form of “infantilization” of the classic reptilian skull, extended to the adult).
Unfortunately, the authors, while noting some of the similarities with the squamata, do not test the affinities of Oculudentavis outside Avialae.

“PS: out of curiosity, I tested Oculudentavis in the large Squamata matrix by Gauthier et al. (2012): it turns out to be a stem-Gekkota.”

Note to readers: Neither Gauthier et al. 2012 nor Dr. Cau tested fenestrasaurs, like Cosesaurus… yet another case of taxon exclusion. With regard to phylogenetic age, fenestrasaur tritosaur lepidosaurs, like Oculudentavis, hatch with the proportions of adults (ontogenetic isometry), so the ontogenetic status of this taxon needs further context (e.g. coeval larger adults or smaller hatchlings)/

Update March 14, 2020:
Readwer TG (below) informs me that Cau’s study did include Cosesaurus. My reply follows: “Thank you, Tyler. Good to know. My mistake. Strange that his Oculudentavis has traits more like the distinctively different Sphenodon and Huehuecuetzpalli, when it looks more like Cosesaurus in every regard. Here’s a guess based on experience: neither he nor Gauthier went to Barcelona to see Cosesaurus, and neither did either reference or cite Peters 2000 or the ResearchGate.net update. And Cau probably used the Xing et al. 2020 ink tracing of Oculudentavis rather than the more detailed DGS tracing I produced (or he could have traced himself), since he did not see the tiny antorbital fenestra [or the twisted quadrate]. Just a guess based on 20 years of experience.” 

PS. Neither Gauthier nor Cau showed their work (e.g. skulls diagrammed with suture interpretations as shown at ReptileEvolution.com links). Therefore we cannot know if or where mistakes were made in their scoring attempts. In a similar fashion, testing revealed a raft of scoring problems with Nesbitt 2011, covered earlier here in the last of a nine-part series. 

Dr. Darren Naish updates his original post in Tetrapod Zoology  
with the following notes:

“A number of experts whose opinions I respect have expressed doubts about the claimed theropod status of the fossil discussed below and have argued that it is more likely a non-dinosaurian reptile, perhaps a drepanosaur or lepidosaur (and maybe even a lizard). I did, of course, consider this sort of thing while writing the article but dismissed my doubts because I assumed that – as a Nature paper – the specimen’s identity was thoroughly checked and re-checked by relevant experts before and during the review process, and that any such doubts had been allayed. At the time of writing, this proposed non-dinosaurian status looks likely and a team of Chinese authors, led by Wang Wei, have just released an article [not linked] arguing for non-dinosaurian status. I don’t know what’s going to happen next, but let’s see. The original, unmodified article follows below the line…”

We can only trust what Dr. Naish reports regarding his private doubts as to the affinities of Oculudentavis. Here he confesses to assuming the ‘opinions’ of ‘relevant experts’ got it right, like all the other journalists who reported on this discovery, rather than testing the hypothesis of Xing et al. 2020, like a good scientist should.

While we’re on the subject of confessing, 
earlier the LRT nested Oculudentavis with Cosesaurus (Fig. 1) despite the former’s much later appearance and derived traits, like the essentially solid palate. I failed to mention the skull of Oculudentavis shares just a few traits with another Late Triassic fenestrasaur, Sharovipteryx (Fig. 1). If Oculudentavis also had a slender neck, like the one in Sharovipteryx, perhaps that was one reason why only the skull was trapped in pine sap, later transformed into amber. Just a guess.

Figure 2. Cosesaurus was experimenting with a bipedal configuration according to matching Rotodactylus tracks and a coracoid shape similar to those of flapping tetrapods. Long-legged Sharovipteryx was fully committed to a bipedal configuration.

Figure 2. Cosesaurus was experimenting with a bipedal configuration according to matching Rotodactylus tracks and a coracoid shape similar to those of flapping tetrapods. Long-legged Sharovipteryx was fully committed to a bipedal configuration.

Note:
with locked down and elongate coracoids, all members of the clade Fenestrasauria were flapping like flightless pterosaurs. Appearing tens of millions of years after the Middle Triassic genesis of fenestrasaurs, who knows what sort of post-crania tiny Early Cretaceous Oculudentavis may have evolved! Known clade members already vary like Hieronymus Bosch fantasy creatures.

The LRT is a powerful tool for nesting taxa
while minimizing taxon exclusion. And it works fast. Feel free to use it in your own studies.


References
Ellenberger P and de Villalta JF 1974. Sur la presence d’un ancêtre probable des oiseaux dans le Muschelkalk supérieure de Catalogne (Espagne). Note preliminaire. Acta Geologica Hispanica 9, 162-168.
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2007.The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Xing L, O’Connor JK,; Schmitz L, Chiappe LM, McKellar RC, Yi Q and Li G 2020. 
Hummingbird-sized dinosaur from the Cretaceous period of Myanmar. Nature. 579 (7798): 245–249.

late arrival:

Wang Wei, Zhiheng Li, Hu Yan, Wang Min, Hongyu Yi & Lu Jing 2020. The “smallest dinosaur in history” in amber may be the biggest mistake in history. Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences: Popular Science News (2020/03/13)
http://ivpp.cas.cn/kxcb/kpdt/202003/t20200313_5514594.html

from B. Creisler’s translated post at dml.cmnh.org:

“Here is the list of problems found by the authors:
Doubts 1. Can the shape of the head prove that it is a bird? 
Doubt 2. Unreasonable Phylogenetic Analysis 
Doubt 3. Birds without antorbital fenestrae? 
Doubt 4. “Birds” with pleurodont teeth? 
Doubt 5. Mysterious quadratojugal bone 
Doubt 6. Scleral bones only found in lizards 
Doubt 7. The bird with the most teeth in history? 
Doubt 8. Body size 
Doubt 9. No feathers? 
Doubt 10. Strange wording and logic chains
We hope that the authors of the paper will respond publicly to these questions as soon as possible. At the same time, it is hoped that the authors of the paper will quickly release the raw data of CT scans, so that other scientists can verify the existing results based on the raw data.”
July Post-Script
Authors retract the paper, according to Nature.

 

7 thoughts on “You heard it here first: Others also doubt the theropod affinities of Oculudentavis

  1. Here is the Chinese paper mentioned by Naish and refuting Xing et al.: Wang, Wei; Zhiheng, Li; Hu, Yan; Wang, Min; Hongyu, Yi; Lu, Jing (13 March 2020). “[Back to the Park] The “smallest dinosaur in history” in amber may be the largest own goal in history”. Institute of Vertebrate Paleontology and Paleoanthropology (in Chinese).

    I haven’t tried to translate the Chinese text, but “largest own goal” suggests that they don’t think much of the due diligence by authors and reviewers of the original paper.

    • Thank you, Tyler. Good to know. My mistake. Strange that his Oculudentavis has traits more like the distinctively different Sphenodon and Huehuecuetzpalli, when it looks more like Cosesaurus in every regard. Here’s a guess based on experience: neither he nor Gauthier went to Barcelona to see Cosesaurus, and neither did either reference or cite Peters 2000 or the ResearchGate.net update. And Cau probably used the Xing et al. 2020 ink tracing of Oculudentavis rather than the more detailed DGS tracing I produced (or he could have traced himself), since he did not see the tiny antorbital fenestra. Just a guess based on 20 years of experience.

      • Please, stop “arguing” what others did or did not: in doing so, you just express your prejudices.
        I scored the taxa based on all published literature, not on photoshop-based color drawings. Yes, I did even read Peters (2000), and I am well aware of your hypotheses published there, but I have not scored taxa based on that paper, because I want to test independently your scenario using a unbiased data set. Your arguments and reconstructions there are not convincing. Sorry if it may hurts, but I cannot follow a paper if it sounds not convincing. Your drawings of those specimens are too vague and subjective: I do not see any of the features you claim from the DGS tracking method. So, I cannot trust them.
        For Oculudentavis, I used the information described in the paper and the high resolution 3D CT-scan model of the whole skull provided by the authors. Photoshop drawing of a JPG figure is not more powerful than a 3D model produced using the CT-scan data from the actual real specimen.
        I never went to Barcelona, of course, but you surely never visited ALL museums worldwide for scoring all your LRT taxa… please, be less hypocritical.

      • Andrea, you wrote: “I cannot follow a paper if it sounds not convincing.” As you confess your mindset (= bias) you should reserve judgement until you see the specimen yourself, or view a high-resolution image, or see the work of Ellenberger on Cosesaurus. Pterosaurs evolved from somewhere. Certainly not archosaurs with their tiny fourth fingers. In 2000 I introduced not one, but four previously known taxa, each were better candidates for pterosaur ancestry in each of four previously published cladograms. The tanystropheid-pterosaur fifth toe also found in Cosesaurus, Sharovipteryx and the rest, was the key to my understanding the relationships that culminated with my identification of the long-stemmed coracoids on Cosesaurus.

        To your point, I cannot trust your scoring of the tiny skull without published images of your interpretation of the skull. You can’t make a statement while keeping such a secret. Also to your point, as a victim of my own bias I made mistakes in 2000, which were corrected in a manuscript from a decade ago available here which colleagues have refused to allow publication, hoping to suppress the hypothesis of a lepidosaurian pterosaur ancestry: https://www.researchgate.net/publication/328388115_Cosesaurus_aviceps_Sharovipteryx_mirabilis_and_Longisquama_insignis_Reinterpreted

  2. I don’t trust your paper because it is impossible to replicate what it claims.
    This is not a bias, it’s the scientific method.

    PS: ironically, I am and have always been open to a non-archosaurian status for pterosaurs. It’s a possible scenario, and I have anything against it. But this does not mean that the LRT is the correct depiction of the pterosaur relationships. The LRT is a non-replicable tree based on a huge amount of subjective and not-testable claims.
    Just because you see something using photoshop does not provide a scientific evidence of anything.

    • Why are you even considering the word ‘trust’? Never trust. Always test. That’s the scientific method. Just look at the fossil and do your own tracings. Your interpretation might not be right. Or it might be right. Someone else will come along to test your observations. That’s the way it goes. I simply introduced this taxon to be considered. I use photos and Photoshop because that is the only way to share information with fellow workers. Otherwise, they would have to trust my opinions, which is not what we want. Right? With regard to the LRT, it is currently your opinion that it is based on non-testable claims. Come back to me after you have tested my claims with your own claims/observations. An observation is either this or that or something else. What, in your opinion, would constitute ‘scientific evidence’ in this case. You are whining without providing an avenue for solution and consensus.

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