Nothing is known of the pterosaur ancestor, Cosesaurus aviceps (Figs. 1, 2), except an exquisite mold that preserves an impression of its bones and soft tissue — along with the softest of soft tissue: a jellyfish also impressed into the matrix (the blob in Fig. 1), and a few trapped air bubbles.
Figure 2. Cosesaurus insitu. No bones are present. This is a natural mold that includes an amorphous blob, a jellyfish, that trapped one foot of this unique specimen. Shown here larger than life size. See figure 1.
Mold fossils are interesting.
Shadows and highlights are the only data. By rotating the light and viewing angle some bones appear and others disappear. So, you need to see such fossils from several angles.
Figure 1. CLICK TO ENLARGE. Cosesaurus reconstructed with enlarged parts of interest including a pes (foot) matching a Rotodactylus track. Here the pelvis is reconstructed according to figure 3. Shown here about life-size.
Yesterday
I reexamined a photo of the pelvis and sacral vertebrae of Cosesaurus. I suspected the pubis and ilium were actually deeper than I previously thought. That hunch paid off (Figs. 3, 4) as DGS tracings showed edges of the pubis and ischium peeking out from both sides of other overlapping bones, sometimes rotated from their original positions.
Figure 3. Cosesaurus pelvic area in situ. Colors added in layers. See figure 4 for reconstructing the slightly scattered and overlapping elements. Red elements are displaced gastralia.
When both pelves matched
that confirmed the new interpretations.
Figure 4. Pelvis and four sacral vertebrae from figure 3 reconstructed. The deeper ischium permits the passage of larger eggs. More than two sacral vertebrae are indicators of bipedal locomotion. Cosesaurus pedes match occasionally bipedal Rotodactylus tracks (Fig. 2).
These new reconstructions and orientations
also more closely match both ancestral and descendant taxa (Fig. 5). These corrections are but a few of the over 100,000 corrections made during the last ten years. The LRT is getting better and better with every improvement like this.
Figure 5. Origin and evolution of the prepubis in tritosaurs.
Cosesaurus aviceps
(Ellenberger and DeVillalta 1974; Ladinian, upper Middle Triassic ~230 mya, ~16cm long), was originally considered an ancestor of birds, then a juvenile Macrocnemus (Sanz and López-Martinez 1984) and finally an ancestor of pterosaurs (Peters 2000a, b; 2009).
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. Ellenberger P 1978. L’Origine des Oiseaux. Historique et méthodes nouvelles. Les problémes des Archaeornithes. La venue au jour de Cosesaurus aviceps (Muschelkalk supérieur) in Aspects Modernes des Recherches sur l’Evolution. In Bons, J. (ed.) Compt Ren. Coll. Montpellier 12-16 Sept. 1977. Vol. 1. Montpellier, Mém. Trav. Ecole Prat. Hautes Etudes, De l’Institut de Montpellier 4: 89-117. Ellenberger P 1993.Cosesaurus aviceps . Vertébré aviforme du Trias Moyen de Catalogne. Étude descriptive et comparative. Mémoire Avec le concours de l’École Pratique des Hautes Etudes. Laboratorie de Paléontologie des Vertébrés. Univ. Sci. Tech. Languedoc, Montpellier (France). Pp. 1-664. Peabody FE 1948. Reptile and amphibian trackways from the Lower Triassic Moenkopi formation of Arizona and Utah. University of California Publications, Bulletin of the Department of Geological Sciences 27: 295-468. Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods. Ichnos 7:11-41. Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336. Peters D 2009.A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330 Sanz JL and López-Martinez N 1984. The prolacertid lepidosaurian Cosesaurus aviceps Ellenberger & Villalta, a claimed ‘protoavian’ from the Middle Triassic of Spain. Géobios 17: 747-753.
Bolet et al. 2020 bring us specimen #2 of ‘Oculudentavis’. “Here we describe a more complete, specimen [GRS-Ref-286278, Fig. 1] that demonstrates Oculudentavis is actually a bizarre lizard of uncertain position. The new interpretation and phylogenetic placement highlights a rare case of convergent evolution rarely seen among reptiles.”
Convergence is rampant within the clade Reptilia.
Whenever they say ‘bizarre’ you know they did not have pertinent taxa on their inclusion list.
When they say ‘uncertain position’ they mean it jumps around on their cladograms depending on the whether characters were ordered, unordered, etc. (see below).
We looked at Oculudentavis #1 several times earlier here, here, here, and elsewhere. and nested it with Cosesaurus, a taxon that has been ignored since March 2020 when it was listed on the Nature comments page.
Bolet et al. correctly nest ‘Oculudentavis‘ #2 close to the basal tritosaur, Huehuecuetzpalli in their figure 3 (reproduced here in Fig. 2). It represents only one of several of their recoveries, as noted below.
Figure 2. Cladogram from Bolet et al. 2020 based on invalid prior cladograms, nesting Oculudentavis with Huehuecuetzpalli.
Unfortunately, due to taxon exclusion and some bad scoring, Oculudentavis #1 does not nest with Oc2 close to Huehuecuetzpalli, but continues to nests with Cosesaurus in the large reptile tree (LRT, 1223+ taxa; subset Fig. 3). Only Oc2 nests with Huehuecuetzpalli (Fig. 3). In order to move Oc2 close to Oculudentavis 21 additional steps are required. So, Oc2 requires a new generic name.
Figure 3. Subset of the LRT focusing on the Tritosauria
From the abstract: “Here we describe a more complete, specimen that demonstrates Oculudentavis is actually a bizarre lizard of uncertain position.”
Unfortunately,Oc2 is not Oculudentavis. The two specimens only vaguely resemble one another. The differences (see below and compare Figs. 1 and 4) turn out to be important.
Its not ‘bizarre’ when correctly nested. Bolet et al. are unaware of the third clade of lepidosaurs, the Tritosauria. The paper describing this clade was rejected several years ago by well-meaning paleo-referees. It could have been useful here.
Sometimes the authors misspell Oculudentavis‘Oculodentavis’. How many of the 10 co-authors were in charge of proofreading?
The authors note the skull proportions are not as tall and attribute that to distortion. Nothing else is distorted in the rest of the skeleton, including the slenderest of bones. That’s the beauty and wonder of amber preservation.
Figure 4. CT scans of Oculudentavis from Xing et al. 2020 and colored here, plus a comparison of Cosesaurus to scale.
Notable differences between Oculudentavis and Oc2.
The maxilla of Oc2 is deeper without an antorbital fenestra.
The palate of Oc2 is much more open and wider with larger choanae.
The basiocciput of Oc2 is inflated.
Oc2 has supratemporals missing in Oculudentavis.
The postorbital extends to the posterior parietal in Oc2.
The quadratojugal is a tiny splinter attached only to the jugal in Oc2.
Oc2 has a vomernasal opening missing from Oculudentavis.
Tiny vomer teeth are present in Oc2.
The vomers contact the maxilla and premaxillae broadly in Oc2. By contrast, the slender medial vomers are squeezed between and above a long posterior extension of the premaxilla in Oculudentavis.
In Oc2 the ectopterygoid continues the posterior rim of the pterygoid transverse process.
From the text: “In its bird-like skull shape (vaulted cranium, tapering rostrum), the skull of Oculudentavis is strikingly different from any known lizard and represents a startling instance of convergent evolution.”
I will remind readers the first several times Cosesaurus (Fig. 5) was described (Ellenberger and de Villalta 1974, Ellenberger P 1978, 1993) it was considered to be a pre-bird. When faced with the possibility that Cosesaurus was a pre-pterosaur (Peters 2000a, b, 2007, 2009), Elllengerger shrugged off the hypothesis. He was too invested. He never considered the possibility, despite years of work with comparative anatomy, just as other workers do today. Cosesaurus also has a vaulted cranium, a tapering rostrum and a rostral crest, by convergence or reversal.
Figure 5. Cosesaurus nasal crest (in yellow).
From the Discussion “Using the squamate data set, the phylogenetic placement of Oculudentavis within Squamata is markedly different depending on how the data is treated.”
“If the characters are treated as ordered, the two specimens form a sister-clade to the limb-reduced, vestigial eyed, fossorial Dibamidae, near the base of Squamata.”
“If characters are treated as unordered, then Oculudentavis is recovered within the crown-squamate clade Toxicofera (snakes, iguanians, anguimorphs, on the stem of mosasaurians and snakes.”
This usually means taxon exclusion. No such problems exist in the LRT, which minimizes taxon exclusion by its large taxon list. Legless Dibamus nests as a highly derived amphisbaenid squamate in the LRT.
“The convergence between Oculudentavis and birds is clearly depicted in the phylomorphospace plot of the amniote data set.”
Unfortunately, no fenestrasaurs (= Cosesaurus and kin including pterosaurs, the most bird-like of all lepidosaurs), are included in the Bolet et al. study.
Even if ALL they had to work with were just Oculudentavis and the new specimen, the differences, especially in the palate, are striking and should have raised the hypothesis that the two taxa were not congeneric.
Keeping fenestrasaurs out of the taxon inclusion list can be attributed to 20 years of suppression and omission. This is what happens when that happens. Mistakes are made.
References Bolet A et al. (9 co-authors) 2020. The tiny Cretaceous stem-bird Oculudentavis revealed as a bizarre lizard. Biorxiv the preprint server for biology. https://www.biorxiv.org/content/10.1101/2020.08.09.243048v1 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. Ellenberger P 1978. L’Origine des Oiseaux. Historique et méthodes nouvelles. Les problémes des Archaeornithes. La venue au jour de Cosesaurus aviceps (Muschelkalk supérieur) in Aspects Modernes des Recherches sur l’Evolution. In Bons, J. (ed.) Compt Ren. Coll. Montpellier 12-16 Sept. 1977. Vol. 1. Montpellier, Mém. Trav. Ecole Prat. Hautes Etudes, De l’Institut de Montpellier 4: 89-117. Ellenberger P 1993.Cosesaurus aviceps . Vertébré aviforme du Trias Moyen de Catalogne. Étude descriptive et comparative. Mémoire Avec le concours de l’École Pratique des Hautes Etudes. Laboratorie de Paléontologie des Vertébrés. Univ. Sci. Tech. Languedoc, Montpellier (France). Pp. 1-664. Li Z, Wang W, Hu H, Wang M, Y H and Lu J 2020. Is Oculudentavis a bird or even archosaur? bioRxiv (preprint) doi: https://doi.org/10.1101/2020.03.16.993949 Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods. Ichnos 7:11-41. Peters D 2000b. 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. Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330 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.
German fossils also preserve wing membranes nicely. Not just in China. 2:18
No need to show old engravings that portray pterosaurs with bat-like ears. 2:34
Basal pterosaurs, like Dimorphodon, were bipeds with giant tree-trunk gripping foreclaws. Pedal digit 5 was not used to frame each uropatagium. Toe 5s are often preserved strongly flexed, used to help support a bipedal configuration, preserved in footprints (Rotodactylus) of pre-pterosaurs. When folded wing membranes nearly completely disappeared due to being stretched only between the elbow and wingtip. 2:54
When you test more taxa, pterosaurs leave dinosaurs and join fenestrasaur, tritosaur, lepidosaurs. These share a long finger 4, a long toe 5, a single sternum, sprawling hind limbs, a pteroid, a prepubis and many other traits not shared with dinosaurs. Sadly we’ve known this for 20 years and Alex Kellner was the peer-reviewer who approved the paper. 3:17
Not all pterosaurs walked on four limbs. We have bipedal track fossils. Only small-clawed beachcombers with flat feet left quadrupedal tracks. 4:09
When tested (ReptileEvolution.com) Archosauria includes only crocs + dinos. Pterosaurs nest with Fenestrasaurus (Cosesaurus), Tritosaurs (Huehuecuetzpalli) and Lepidosaurs. 5:30
Basal bipedal crocs were not dinosaur mimics. The both evolved from a last common ancestor that was bipedal. 5:40
The basal croc at 5:46 is not one at all, but from another family of archosauriformes.The ankle bone arrangement of pterosaurs and dinosaurs is by convergence. It happens often enough when reptiles become bipedal. Sharovipteryx for example. When scientists pull this trick, it’s called “Pulling a Larry Martin” to honor the Kansas professor who delighted in calling young know-it-alls out. 5:54
Actually dinosaurs (archosauromorphs) and pterosaurs (lepidosauromorphs) separated from one another some 335 million years ago, when the first amniotes (=reptiles), like Silvanerpeton, appeared. 5:50
The hole in the hip socket separates dinos from crocs. Like lizards and turtles and humans, pterosaurs have no hip socket hole. Same goes for the long humeral (deltopctoral) crest. No plesiomorphic reptile has ever been put forth as the last common ancestor of pterosaurs and dinosaurs, except the aforementioned Silvanerpeton. 6:02
No pterosaurs flew with hind legs trailing behind. As lepidosaurs pterosaurs had sprawling hind limbs that extended laterally, like horizontal stabilizers on modern aircraft. All preserved wing membranes show they stretched only between the wingtip and elbow, with a short fuselage fillet to mid thigh. Long narrow wings reduced drag. 11:33
No pterosaur took off by doing a dangerous jumping push-up. Better to start flapping with wings out while leaping, as birds do, instead of opening the wings later from a closed and ventral start. 11:56
The largest pterosaurs got to be that size, just as giant birds do today, because they gave up flying, as shown by their clipped wings (vestigial distal wing finger bones). They could still use their wings for thrust while running, like the earlier video images of the running swan. 12:06
If it’s tough enough for flapping swans, what the animators show at 12:40 (giant azhdarchid quad leap takeoff) is impossible, especially with ‘clipped’ wings. By the way, the elbows rose above the leading edge, creating camber. Also by the way, when Paul MacCready made his third-size flying model of Quetzalcoatlus, he added wingspan to make it work. https://pterosaurheresies.wordpress.com/2020/04/12/can-volant-fossil-vertebrates-inspire-mechanical-design/
Pterosaur wing membranes have less of an airplane-like camber and more of an ornithopter appearance, with a thick leading edge, but the rest is a thin membrane that folds to near invisibility. Forcing the air down and back, as in ornithopters, has the opposite and equal reaction of forcing the ornithopter/pterosaur up and forward. Unfortunately the animators for the AMNH used flat wings in flight, not dorsally bowed wings. 13:15
Many small pterosaurs flapped as often as small birds do (creating what should have been a blur in the animation). 14:30
Why did pterosaur ancestors learn to fly? Impressing females, rivals and predators (the video skips that step). That story is told by flapping, nonvolant Cosesaurus. Link here: http://reptileevolution.com/cosesaurus.htm
We have more than 150 pterosaur species right now. Those professors are not counting the small Solnhofen adults and multiple species within a single genus. 17:40
Short summary:
Just about everything the AMNH included in their pterosaur video was outdated and wrong with no evidence backing their traditional claims. So, should the AMNH retract this video? I mean, children are watching… and the AMNH should care about their public outreach.
Part 2
If Oculudentavis (Figs. 1, 2) is a lepidosaur based on the Cau blogpost 2020 and Li et al. 2020 trait list (see below), how does the basalmost pterosaur in the LRT, Bergamodactylus (Fig. 2), match that list?
Figure 2. Skulls of Oculudentavis and Bergamodactylus compared. Not to scale. Note the dark blue palatine in Oculudentavis shows through the antorbital fenestra.
“Absence of anti-orbital window.” AOF present in both (Fig. 2, note palatine (deep blue) is visible through AOF in Oculudentavis).
“Quadrate with large lateral concavity. This character is not typical of dinosaurs, but of lepidosaurs.”Not discernibly concave in crushed Bergamodactylus.
“The maxillary and posterior teeth of the maxilla extend widely below the orbit.”Last maxillary tooth below orbit in both.
“Dentition with pleurodont or acrodont implant.”Thecodont implantation in Bergamodactylus.
“Very large post-temporal fenestra.” As in Bergamodactylus.
“Spoon-shaped sclerotic plates is typical of many scaled lepidosaurs.”Plates much smaller in Bergamodactylus.
“Coronoid process that describes a posterodorsal concavity of the jaw reminds more of a lepidosaur than a maniraptor.”As in Bergamodactylus.
“Very small size comparable to those of the skulls of many small squamata found in Burmese amber.”Much smaller skull than Bergamodactylus.
Here’s the Ling et al. 2020 list:
“absence of an antorbital fenestra” AOF present in both
“The ventral margin of the orbit is formed by the jugal.” Actually, the lacrimal, jugal and postorbital. It’s a big orbit, as in Bergamodactylus.
“Another unambiguous squamate synapomorphy in Oculudentavis is the loss of the lower temporal bar.”Actually the lower bar is formed by the tiny loose quadratojugal, lateral to the quadrate in both taxa.
FIgure 3. CT scan model from Li et al. 2020, who denied the presence of a quadratojugal and an antorbital fenestra, both of which are present. Colors applied here.
Only a few of the above are LRT traits.
The LRT compares 1717 taxa with 230 other characters and nests Early Cretaceous Oculudentavis with Middle Triassic Cosesaurus, a few nodes away from Late Triassic Bergamodactylus.
References Li Z, Wang W, Hu H, Wang M, Y H and Lu J 2020. Is Oculudentavis a bird or even archosaur? bioRxiv (preprint) doi: https://doi.org/10.1101/2020.03.16.993949 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.
Bonus video on becoming a PhD. You’re doing research on what you set for 3-4 years, sort of like creating and supervising the LRT for the last 9 years.
It happened over the past several months to Xing et al. 2020 after they published in Nature on their hummingbird-sized ‘dinosaur’ in amber, Oculudentavis. Then, oops! Everyone else recognized the specimen as a lepidosaur. Last week Nature and the publicly-shamed authors retracted the paper with a fair amount of bad press.
Meanwhile, on a more personal note…
imagine examining fossils across the ocean without a science degree and ‘discovering’ four overlooked ancestors to pterosaurs (Peters 2000; Fig. 2). None had been identified before and no others have been identified since. Actually these pre-pterosaurs were recovered by adding their data to four previously published phylogenetic analyses, not by finding fossils in the field. Unfortunately (and this is true), for the next twenty years that paper, that discovery and several that followed (Peters 2002, 2007, 2009) were never cited in a supportive sense. Instead these peer-reviewed papers were shunned and ignored.
Worse yet,
imagine a gathering of PhDs rising against you online. Some call you a ‘hack’ even though you followed all the rules and did all the work with the proper citations, acknowledgements and peer review. When one studies specimens and writes papers, the furthest thing on your mind is a future with online shaming from the cancel culture.
Figure 1. Scene from Animal House after Otter walks into a hotel room with roses for his rendezvous, only to meet the five frat boys ready to deliver a little punishment.
All is not lost. Patience is the watchword here. No one else can ‘discover’ these interrelationships (Fig. 2). They are time-stamped in the academic literature. Perhaps the best thing one can realize is: the enmity coming from other scientists turns out to be a relatively common phenomenon.
The question is:
why do some scientists demonize and shun discoverers?
Figure 2. The lineage of pterosaurs recovered in Peters 2000 and from the large reptile tree. Huehuecuetzpalli. Cosesaurus. Longisquama and MPUM 6009 (Bergamodactylus).
“We will reduce somebody to a label. We’ll reduce somebody to the worst tweet that they ever wrote. We’ll demonize them and then we’ll de-humanize them, because we’ve just destroyed somebody and we don’t want to feel bad about destroying them so we call them ‘sociopath’ or something.”
“It’s a whole mental trick we play on ourselves. Like, cognitive dissonance. We’re good people, but we just destroyed somebody. So how do we make sense of that?”
“So it’s all about labeling and reducing and demonizing people we don’t like.”
Then Joe Rogan pipes in: “And it’s also an excuse to be a real asshole. Like all you have to do is find a reason to unleash your fury on people. And it’s a free shot.”
Whenever someone calls you a ‘hack’, try to see things from their point-of-view. Do they have a point? Is there something you have to do to ‘clean up your act?’ If so, then clean up your act. Do more than is expected. Add taxa. Trace details. Show your work. Double check your results for errors. Write to experts for their advice (but be wary if they try to send you snipe hunting). After you’ve done all that, all to no avail, then consider the following…
Sometimes personal attacks are the result of unfulfilled expectations.
After all, some paleontologists spend a lot of money and many years getting a PhD only to find out professorial jobs are as rare as bird teeth. Discoveries are even harder to come by, whether in the field or by fossils occasionally sent to them.
So, it’s no wonder PhDs are pissed off
when a nobody from a small town in middle America starts harvesting the literature, adding taxa to a growing online vertebrate cladogram and making discoveries several times a week. That cladogram, the core of ReptileEvolution.com, now exceeds in size and breadth any vertebrate study ever published (samples from 1700+ fish to humans are included). New insights were recovered just by testing taxa together that have never been tested together before (like pterosaurs and lepidosaurs, Fig. 2).
The unfortunate fact is: the list of discoveries waiting to be discovered
is limited and it gets shorter everyday. Today’s young paleontologists earned their PhDs in order to make those rare discoveries. So, imagine their wrath when an unschooled outsider showed them their expensive and time-consuming education was not really necessary, at least at this stage in paleontology. What was necessary was a comprehensive review of the literature and a single wide gamut test to reveal where taxon exclusion had resulted in traditional false positive results.
Getting back to Animal House for a moment… Otter thought he was going to get a little romance the night he opened the door to a motel room, with the cheerful line, “It’s “Mr. Thoughtful” with a dozen roses for… you…” only to be met by a cadre of frat boys ready to pummel him (Fig. 1). Likewise, twenty years ago when I recovered four pterosaur ancestors, I thought good things would follow. Alas, that still has not happened. Nothing but ostracizing and enmity has followed.
Sadly, some of the things you learn in paleontology
are not found in textbooks. One is the extremely slow pace of acceptance in this field.
Remember it took paleontologists 150 years
to elevate the tails of tail-dragging dinosaurs and to realize birds were dinosaurs. It will take them more than twenty years to realize pterosaurs were lepidosaurs. Unlike other sciences, paleontological discoveries and recoveries, especially from outsiders, are not welcome.
So, if you make a discovery, take your punishment cheerfully and maintain your scientific work ethic. Be patient. If you play it straight, and put the work in, you already know how this movie is going to end. Starting off, your only allies will come out of the ‘Delta House‘ fraternity, but soon you’ll have the whole audience on your side.
Good luck on your scientific journey.
Rest assured that others have been through whatever you’re going through now.
Hope this ‘futile and stupid gesture’ helps.
Postscript:
It’s no wonder that some workers thought Oculudentavis was a bird, while others thought it was a lepidosaur. After testing all known candidates, it turns out Oculudentavis was a late-surviving sister to Cosesaurus (Fig. 2), which was originally and mistakenly considered a Middle Triassic bird ancestor (Ellenberger and DeVillalta 1974). Later Peters (2000, 2007) recovered Cosesaurus as a lepidosaur and a flapping pterosaur ancestor. So, these related taxa tell the same story.
All this confusion over Oculudentavis could have been avoided
if the pterosaur community had not shunned and shamed the results of Peters 2000, 2002, 2007, 2009. Due to that suppression the bird-like lepidosaur, Cosesaurus, was not on the radar of Xing et al. and it was not tested to ascertain relationships.
And that’s how the ripples radiate.
Rarely to never cited 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 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301. Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27. Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29:1327-1330. 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.
And finally this carbon copy reply to a recent (2020) TetZoo blogpost by PhD Darren Naish, doubling down on his earlier (2012) blogpost, “Why the World Has to Ignore ReptileEvolution.com“. This was followed by a long list of comments by a cadre of angry paleontologists.
“Well, fellas, that’s a lot to drink in. Thank you for all the attention.
ReptileEvolution.com is an online experiment in which I learn as I go. Just like a professional. True, I made over 100,000 errors in scoring or drawing over the last nine years. In understand in science that’s part of the process.
A few points worth considering:
Taxon exclusion is the issue I bring up over and over again. Just add pertinent taxa, score correctly and see what PAUP delivers. Shouldn’t be too hard. Add some placoderms to some catfish taxa. Add some caseasaurs to millerettids. And show your work.
Cau’s study on pterosaurs arising from Scleromochlus (a basal bipedal crocodylomorph) seems odd given that the hand is so small in Scleromochlus and the foot lacks a long toe 5, etc. etc. No illustrations accompany the cladogram, so we don’t know what characters were correctly or incorrectly scored for Sharovipteryx and Cosesaurus. I show my work. Ellenberger thought Cosesaurus was a Middle Triassic bird ancestor and I could not convince him otherwise. So whatever the problem is, it’s common and I’m used to it.
Yi qi: seriously? Please send data on both ulnae, both radii and the both styliforms. I will make the change to create the flying dragon if you can show valid data. Ball is now in your court.
Figure 3. Darren Naish did not like the more precise tracing made by yours truly. He though I was seeing things. The tracing at upper left is the original published tracing by the fossil describers.
Hey, Darren, what’s wrong with that tracing of Jeholopterus skull? (Fig. 3) I provided a competing tracing (upper left hand corner). Is that all you got? After 17 years mine is still accurate and all the parts fit together in appropriate patterns. Bennett’s anurognathid skull, which you prefer, mistook a maxilla for a giant scleral ring. But the right giant scleral ring was never found. Nor were any giant scleral rings ever found on any other anurognathids. Let me know if and when you find one.
Figure 4. Chicken skull (Gallus gallus) with fused and semi-fused skull bones colorized. Postorbital = orange. Squamosal = tan. Lacrimal = brown. Prefrontal = purple. Quadrate = red. No one else has ever attempted to do something similar.
re: that chicken skull colored photo {FIig 4}: please provide a competing image that shows what a ‘real’ chicken skull is all about. I’d like to know where the errors are so I can fix them. I prefer to use rather than create.
re: genomics vs. phenomics. Didn’t the taxon list in Afrotheria cause you to wonder, even a little bit? Gene studies produce false positives over deep time. You can test it yourself. If an amateur can do it, so can you.
If I forgot to address a favorite criticism, let me know. You guys provided a long list. At present, it’s better to be brief and to the point.
The large reptile tree (1712+ taxa) plus the pterosaur tree and therapsid skull tree all produce cladograms that recover sister taxa that actually look like each other (not like pterosaurs arising from Scleromochlus). All three are constantly being updated as I find errors. The LRT demonstrates you can lump and split 1712 taxa using only 230 multistage characters. That’s a fact. More taxa are more important than more characters. That’s a fact.
This is something the paleo community has asked for. But the order of taxa is not what you asked for. Where is the competing study? If you’ve been sitting on your hands and/or writing to Darren Naish, you’ve been wasting your time. Do what you are paid to do. Or wait until you retire and have gobs of time, like me. — David Peters”
O’Connor et al. 2020 are not giving up without a fight.
Now they are arguing against a published objection (Li et al. 2020) to their interpretation of Oculudentavis as a strange tiny bird encased in Early Cretaceous Burmese amber. Citation and excerpts are below. You have to admire their courtesy while defending their hypothesis with every weapon they have… except the correct one.
From the O’Connor et al. abstract: “We welcome any new interpretation or alternative hypothesis regarding the taxonomic affinity of the enigmatic Oculudentavis khaungraae. However, here we demonstrate that Li et al. have failed to provide conclusive evidence for the reidentification of HPG-15-3 as a squamate. We analyse this specimen in a matrix that includes a broad sample of diapsid reptiles and resolve support for this identification only when no avian taxa are included. Regardless of whether this peculiar skull belongs to a tiny bird or to a bizarre new group of lizards, the holotype of Oculudentavis khaungraae is a very interesting and unusual specimen, the discovery of which represents an important contribution to palaeontology.”
‘Regardless’ indeed, as a scientist it’s your job to figure this out. This time it’s not either this or that… it’s something else, a third alternative nobody wants to talk about.
FIgure 1. CT scan model from Li et al. 2020, who denied the presence of a quadratojugal and an antorbital fenestra, both of which are present. Arrow points to antorbital fenestra Colors applied here. In the LRT Oculudentavis nests with Cosesaurus, a pterosaur precursor. See figure 2.
Interesting that O’Connor et al. bring up taxon exclusion, yet keep excluding the taxa that would resolve this stand-off, members of the Fenestrasauria (Peters 2000). The O’Connor et al. taxon list was ‘broad’, but not broad enough.
Figure 2. Cosesaurus flapping animation. This sister to Oculudentavis in the LRT was a flapping lizard and a pterosaur precursor provided with locked down coracoids, a aternum, strap-like scapulae, an antorbital fenestra a large orbit and bulbous cranium.
From the O’Connor et al 2020 introduction. “We welcome any new interpretation or alternative hypothesis regarding the taxonomic affinity of the enigmatic Oculudentavis khaungraae.”
No they don’t! They were sent an alternative hypothesis the day after publication. (Not whining. Just stating fact in the face of all their righteous signaling).
“Several of the squamate morphologies described by Li et al. were noted by ourselves in the original manuscript (e.g., pleurodont dentition, morphology of the eye)1. However, we will argue that other features which Li et al. describe as unusual for archosaurs are not incompatible with our original interpretation.”
The solution continues to be the third choice, which both sides continue to overlook (= taxon exclusion).
From the O’Connor et al. text, “Li et al. criticize our phylogenetic analysis yet provide none themselves.”
Good point! A phylogenetic solution is paramount. Otherwise you’re “Pulling a Larry Martin” trying to make your argument with possibly convergent traits, not last common ancestry, which, when done right, is irrefutable.
The O’Connor et al. text continues, “However, this does highlight a weakness of a majority of phylogenetic analyses utilized to describe new taxa. If a new specimen is identified as a bird it is analysed in a matrix targeted at birds; if the specimen is identified as a lizard, it is analysed in a matrix targeted at lizards. Descriptions of new taxa rarely include phylogenetic datasets targeted at higher level relationships such as all of Reptilia or Amniota that would be capable of testing alternative placements.”
Another excellent point! That’s why the large reptile tree (LRT, 1697+ taxa) is online and available for anyone to use, precisely for problem taxa, like Oculudentavis.
O’Connor et al. report, “However, removal of all avian taxa results in Oculudentavis being resolved among squamates.”
That’s interesting! (and supports Peters 2007). By the way, such a phylogenetic leap rarely happens in the LRT. Removing large proximal clades usually results in the next closest clade nesting the enigma taxon.
O’Connor et al. conclude: “Oculudentavis may represent an outstanding case of convergent evolution between squamates and birds, the likes of which biologists have rarely seen before.”
Well, yes, if you’re referring to flapping, flying lizards (aka ‘pterosaurs’; Peters 2007). This citation is rare due to academic suppression.
Unfortunately, O’Connor et al. are still missing the headline of this story: Oculudentavis is a late-surviving member of the Middle Triassic radiation that produced pterosaurs. The arose from an overlooked third clade of Lepidosaurs, some on which became protorosaur mimics. Others became archosaur mimics.
“However, regardless of whether this peculiar skull belongs to a tiny bird or to a bizarre new group of lizards, the holotype of Oculudentavis khaungraae is a very interesting and unusual specimen, the discovery of which represents an important contribution to palaeontology.”
It won’t be ‘bizarre’ once you understand what Oculudentavis is: a sister to the lepidosaur tritosaur fenestrasaur Cosesaurus. Just expand that taxon list and come to an agreement.
Again, when someone uses the word “bizarre” they have not included all the pertinent taxa. It’s sign they are giving up. Nothing is bizarre in the LRT. All enigmas are nested. No taxon stands alone.
This is what citation avoidance and suppression results in. Neither party understands what they have here. We looked at this exact problem yesterday.
We looked at the Oculudentavis controversy
earlier here, here, here, here and here. And the story has yet to reach a conclusion.
Figure 3. The origin of pterosaurs now includes Kyrgyzsaurus, nesting between Cosesaurus and Sharovipteryx.
Postscript: The post-crania of Oculudentavis remains unknown. It could resemble anything from Cosesaurus (Fig. 3) through pterosaurs, given its Early Cretaceous age and the variety we already find in the clade Fenestrasauria, from which it arose.
References Li Z, Wang W, Hu H, Wang M, Y H and Lu J 2020. Is Oculudentavis a bird or even archosaur? bioRxiv (preprint) doi: https://doi.org/10.1101/2020.03.16.993949 (Not cited in O’Connor et al. 2020) O’Connor J Xing, Chiappe L, Schmitz L, McKellar R, Li G and Yi Q 2020. Reply to Li et al. “Is Oculudentavis a bird or even archosaur?” bioRxiv 2020.06.12.147041 (preprint) 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.
Cosesaurs (basal fenestrasaurs)
(Figs. 1–3) are popping up everywhere lately!
Figure 1. MIddle Triassic Cosesaurus. Double its size and it would be close to Early Triassic Elessaurus. See figure 6.
Earlier we looked at a tiny Early Cretaceous cosesaur skull in amber originally mistaken for a bird/dinosaur: Oculudentavis.
Figure 2. Elessaurus hind limb elements gathered together to scale. Some original scale bars were off by 2x.
Today De-Oliveira et al. 2020 bring us a new Early Triassic cosesaur, Elessaurus gondwanoccidens (UFSM 11471, Figs. 2, 3) known from a hind limb, pelvis, partial sacrum and proximal caudal vertebrae. Cosesaurus was a derived tanystropheid, close to Langobardisaurus, but was not included in the De-Oliveira taxon list.
Figure 3. Elessarus pes compared to Cosesaurus to scale and x2. Note differences between original tracing and DGS tracing. Digit 5 was not lost. It is tucked beneath the metatarsals and was not scored in the LRT.
In the De-Oliveira et al. published cladogram
(Fig. 4) Elessaurus nests basal to the Tanystropheidae (= Macrocnemus, Amotosaurus, Tanystropheus, Tanytrachelos and Langobardisaurus) a clade they derive from Protorosaurus and Trilophosaurus. in one cladogram (Fig. 4), but not in the other (Fig. 5). The authors reported, “In addition, the new specimen presents some features only found in more specialized representatives within Tanystropheidae, such as the presence of a well-developed calcaneal tuber with a rough lateral margin.”
Figure 4. Published cladogram by De-Oliveira et al. 2020. Note different nesting than their SuppData cladogram in figure 5.
By contrast, in the De-Olveira et al. SuppData cladogram Elessaurus nests without resolution within the Rhynchosauria (Fig. 5). Distinct from the first analysis (Fig. 4), this (Fig. 5) included the drepanosaur ancestor, Jesairosaurus, and the derived macrocnemid,Dinocephalosaurus. The authors reported, “In this second analysis, Elessaurus adopts different positions among the MPTs, it is recovered, e.g. within Archosauriformes, as a sister-taxa of Allokotosauria+Archosauriformes and an early rhynchosaur.” This is a red flag indicating major problems in scoring and taxon exclusion.
Figure 5. Cladogram from DeOliveira et al. 2020 with colors added to show distribution and mixing of Lepidosauromorpha and Archosauromorpha clades in the LRT. Many of these purported sister taxa do not look alike! Strangely, here Elessaurus nests with rhynchosaurs, not tanystropheids (Fig. 2). The taxon in pink had to be looked up and revised here.
By contrast,
in the large reptile tree (LRT, 1661+ taxa), Elessaurus nests as a derived tanystropheid, alongside Cosesaurus(Fig. 1). a smaller Middle Triassic taxon omitted from the original study. The authors mistakenly considered tanystropheids to be archosauromorphs, again due to taxon exclusion. Despite the many traits that converged with archosauromorph protorosaurs, tanystropheids are tritosaur lepidosaurs, derived from Huehuecuetzpalli(Fig. 7) and Tijubina. In the LRT, adding taxa does not create chaos. New taxa neatly take their place within the current tree topology. By omitting Cosesaurus, the authors omitted the most similar taxon to Elessaurus and all the added information included herein.
The cladogram by De-Oliveira et al. shuffles lepidosauromorphs
with archosauromorphs without an understanding of their Viséan split. As a result, several purported ‘sisters’ in figure 5 do not look alike, but apparently nested together by default. Based on these ‘odd bedfellows’ I suspect the authors borrowed another worker’s cladogram without checking scores or examining results.
From the abstract: “The origin and early radiation of Tanystropheidae, however, remains elusive.”
This is false. We know the origin of Tanystropheidae back to Cambrian chordates. Taxon exclusion by the authors prevents them from recovering both distant and proximal sister taxa.
“Here, a new Early Triassic archosauromorph is described and phylogenetically recovered as the sister-taxon of Tanystropheidae.”
By contrast, in the LRT Elessaurus is a derived fenestrasaur close to Cosesaurus, a taxon excluded by the authors. We know cosesaur tracks (= Rotodactylus, Fig. 6) go back to the Early Triassic and some were much larger than Cosesaurus.
Figure 6. Click to enlarge. Scaling a quadrupedal Cosesaurus to the larger Rotodactylus tracks from Haubold 1983. Quadrant represents center of balance in the closeup foot. Graphic representation of a butt joint is nearby.
More from the abstract:
“The new specimen, considered a new genus and species, comprises a complete posterior limb articulated with pelvic elements. It was recovered from the Sanga do Cabral Formation (Sanga do Cabral Supersequence, Lower Triassic of the Parana Basin, Southern Brazil), which has already yielded a typical Early Triassic vertebrate assemblage of temnospondyls, procolophonoids, and scarce archosauromorph remains. This new taxon provides insights on the early diversification of tanystropheids and represents further evidence for a premature wide geographical distribution of this clade. The morphology of the new specimen is consistent with a terrestrial lifestyle, suggesting that this condition was plesiomorphic for Tanystropheidae.”
Likewise,Cosesaurus and related fenestrasaurs in the LRT are terrestrial taxa, distinct from other tanystropheids, all arising from tritosaur lepidosaurs like Tijubina and Huehuecuetzpalli.
Figure 7. The father of all pterosaurs and tanystropheids, Huehuecuetzpalli, a late survivor in the Early Cretaceous from a Late Permian radiation.
Larger quadrupedal cosesaurs,
like Elessaurus, had two sacrals (Fig. 1). Smaller bipedal cosesaurs (Fig. 1) had four. Both had anterior processes on the ilium, not longer than the acetabulum width, distinct from non-fenestrasaur tanystropheids.
PS
Figure 2 in De-Oliveira has a scale bar problem in their figure 2 (explained here in Fig. 2).
References De-Oliveira TM, Pinheiro FL, Da-Rosa AAS, Dias-Da-Silva S and Kerber L 2020.
A new archosauromorph from South America provides insights on the early diversification of tanystropheids. PLoS ONE 15(4): e0230890
Earlier we looked at a Oculudentavis, a late-surviving cosesaur in Early Cretaceous Burmese amber. I noted it had just a few traits closer to another fenestrasaur, Sharovipteryx (Fig 2).
Figure 1. DGS tracings of two amber entombed Early Cretaceous sharovipterygids.
Today, two unnumbered, unnamed, undescribed Early Cretaceous fenestrasaurs with even more sharovipterygid traits from the same Burmese amber. These specimens have huge eyes, a larger naris, a small antorbital fenestra, gracile postorbital bones, long cervicals with robust cervical ribs. That gray sickle-shaped area appears to represent the same sort of extendable hyoids seen in Sharovipteryx that extend the neck skin to form canard wing membranes or strakes (Fig. 2). Once again, these poor saps got their head stuck in the resin. The rest of the body was lost to the ages.
For comparison, a complete Sharovipteryx
(Fig. 2) is known from Late Triassic strata, coeval with the first pterosaurs, both derived from Cosesaurus, a lepidosaur tritosaur fenestrsaur.
Figure 3. Sharovipteryx reconstructed. Note the flattened torso.
References No scale bar, No citation, No museum number, Owner unknown.
Li et al. 2020 bring us higher resolution scans of the putative tiny toothed ‘bird’ (according to Xing et al. 2020) Oculudentavis (Fig. 1). Following a trend started here a week ago, Li et al. support a generalized lepidosaur interpretation, but then tragically overlook/deny details readily observed in their own data (Fig.1).
FIgure 1. CT scan model from Li et al. 2020, who denied the presence of a quadratojugal and an antorbital fenestra, both of which are present. Colors applied here. The previously overlooked jugal-lacrimnal suture becomes apparent at this scale and presentation.
Li et al. deny the presence of a clearly visible antorbital fenestra.
They report, “One of the most bizarre characters is the absence of an antorbital fenestra. Xing et al. argued the antorbital fenestra fused with the orbit, but they reported the lacrimal is present at the anterior margin of the orbit. This contradicts the definition of the lacrimal in birds, where the lacrimal is the bone between the orbit and antorbital, fenestra. In addition, a separate antorbital fenestra is a stable character among archosaurs including non-avian dinosaurs and birds, and all the known Cretaceous birds do have a separate antorbital fenestra.”
Contra Li et al.
a standard, ordinary antorbital fenestra is present (Fig. 1 dark arrow) and the lacrimal is between the orbit and antorbital fenestra. This is also the description of the antorbital fenestra and fenestrasaurs, like Cosesaurus (Fig. 2), Sharovipteryx and pterosaurs (Peters 2000).
Li et al. report, “The ventral margin of the orbit is formed by the jugal.”
Contra Li et al.
the lacrimal is ventral to half the orbit (Fig. 1). The jugal is the other half. The suture becomes visible at the new magnification.
Li et al. report, “Another unambiguous squamate synapomorphy in Oculudentavis is the loss of the lower temporal bar.”
Contra Li et al.
the lower temporal bar is created by the quadratojugal, as in Cosesaurus, Sharovipteryx and pterosaurs. In Oculudentavis the fragile and extremely tiny quadratojugal is broken into several pieces. DGS (coloring the bones) enables the identification of those pieces (Fig. 1).
Figure 2. Cosesaurus with colors applied. Compare to figure 1.
Li et al. conclude, “Our new morphological discoveries suggest that lepidosaurs should be included in the phylogenetic analysis of Oculudentavis.”
Contra Li et al.
these are all false ‘discoveries’.
Also note that Li et al. cannot discern
which sort of lepidosaurs should be tested in the next phylogenetic analysis of Oculudentavis. That’s because lepidosaur tritosaur fenestrasaurs, like Cosesaurus (Fig. 2), are not on their radar. That’s because pterosaur referees have worked to suppress the publication of new data on Cosesaurus and kin. And that’s what scientists get for not ‘playing it straight.’
References Li Z, Wang W, Hu H, Wang M, Y H and Lu J 2020. Is Oculudentavis a bird or even archosaur? bioRxiv (preprint) doi: https://doi.org/10.1101/2020.03.16.993949 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.
You decide.
Here are two CT scans (Figs. 1, 2), one from the left and the other from the right with overlays interpretating skull sutures, enlarged from the previous presentation.
Figure 1. CT scan from Xing et al. 2020, colors added to show antorbital fenestra. Note the wrinkling of the maxilla (green) reacting to the twisting of the tiny, fragile skull during taphonomy.
Now, perhaps, you can see the difficulty
in determining whether or not an antorbital fenestra was present in Oculudentavis. DGS makes things easier by segregating bones with color. All interpretations are up for discussion. I hope you’ll agree, DGS overlays facilitate such discussions better than line tracings do.
Figure 2. CT scan of Oculudentavis from Xing et al. 2020, colors added. Antorbital fenestra here is mailer than in Cosesaurus, but still visible.
The antorbital fenestra in Cosesaurus (Fig. 3) and Oculudentavis (Figs. 1, 2) is only one trait among many linking these basal members of the Fenestrasauria with derived members in the Pterosauria. No single trait is ‘key’. Between the Middle Triassic (Cosesaurus) and the Early Cretaceous (Oculudentavis) the antorbital fenestra could have grown larger, as it did in pterosaurs, or disappear entirely. It’s only one trait. No one trait is that important in a phylogenetic analysis that includes 238 traits.
Figure 3. Cosesaurus nasal crest (in yellow).
Some workers doubt
that Cosesaurus (Fig. 3) had an antorbital fenestra. Again, you decide. The large reptile tree (LRT, 1656+ taxa) nests Cosesaurus basal to pterosaurs and other fenestrasaurs.
Final thought: With cosesaurs in the Early Cretaceous, it might seem possible to spawn a second origin for pterosaur-like flyers… but that never happened. Only in the Middle Triassic were genes and environs in lock-step with one another to produce basal pterosaurs.
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. Ellenberger P 1978. L’Origine des Oiseaux. Historique et méthodes nouvelles. Les problémes des Archaeornithes. La venue au jour de Cosesaurus aviceps (Muschelkalk supérieur) in Aspects Modernes des Recherches sur l’Evolution. In Bons, J. (ed.) Compt Ren. Coll. Montpellier 12-16 Sept. 1977. Vol. 1. Montpellier, Mém. Trav. Ecole Prat. Hautes Etudes, De l’Institut de Montpellier 4: 89-117. Ellenberger P 1993.Cosesaurus aviceps . Vertébré aviforme du Trias Moyen de Catalogne. Étude descriptive et comparative. Mémoire Avec le concours de l’École Pratique des Hautes Etudes. Laboratorie de Paléontologie des Vertébrés. Univ. Sci. Tech. Languedoc, Montpellier (France). Pp. 1-664. Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods. Ichnos 7:11-41. Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336. Peters D 2009.A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330 Sanz JL and López-Martinez N 1984.The prolacertid lepidosaurian Cosesaurus aviceps Ellenberger & Villalta, a claimed ‘protoavian’ from the Middle Triassic of Spain. Géobios 17: 747-753. 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.
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.
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).
Absence of anti-orbital window. [not true, click here]
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]
The maxillary and posterior teeth of the maxilla extend widely below the orbit.
Dentition with pleurodont or acrodont implant.
Very large post-temporal fenestra.
Spoon-shaped sclerotic plates is typical of many scaled lepidosaurs.
Coronoid process that describes a posterodorsal concavity of the jaw reminds more of a lepidosaur than a maniraptor.
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 Naishupdates 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.
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
“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.”
The Pterosaur Heresies 