AMNH pterosaur video: due for an Oculudentavis-type retraction

Recently (March 2020 to July 2020)
Xing et al. 2020 agreed to retract their paper on Oculudentavis because they said it was a bird and it turned out to be a lepidosaur.

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

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

Also recently (July 31, 2020)
the American Museum of Natural History posted a YouTube that reported pterosaurs were archosaurs (= birds, dinosaurs and crocs) and pterosaurs turn out to be lepidosaurs. whenever tested with typically excluded taxa. Should the AMNH be held to the same rigorous standards demonstrated by Nature magazine and Xing et al. 2020? Here’s the evidence:

Full set of comments on the AMNH pterosaur video (above)
are copied below.

Lots of misinformation here. Traditional myths are hard to kill.

No pterosaur wing membrane ever extends to the knee or thigh and no single uropatagium stretched between the lateral pedal digits.

No pterosaurs had their eyeballs in the front half of their skulls. 1:16

Size actually goes down to hummingbird-sized 1:41

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 ( 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.

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:

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

A cladogram that tests 250 different pterosaurs can be found here:

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.

Figure 2. Skulls of Oculudentavis and Bergamodactylus compared. Not to scale. Note the dark blue palatine in Oculudentavis shows through the antorbital fenestra.

Here’s the Cau list:

  1. “Absence of anti-orbital window.” AOF present in both (Fig. 2, note palatine (deep blue) is visible through AOF in Oculudentavis).
  2. “Quadrate with large lateral concavity. This character is not typical of dinosaurs, but of lepidosaurs.” Not discernibly concave in crushed Bergamodactylus.
  3. “The maxillary and posterior teeth of the maxilla extend widely below the orbit.” Last maxillary tooth below orbit in both.
  4. “Dentition with pleurodont or acrodont implant.” Thecodont implantation in Bergamodactylus.
  5. “Very large post-temporal fenestra.” As in Bergamodactylus.
  6. “Spoon-shaped sclerotic plates is typical of many scaled lepidosaurs.” Plates much smaller in Bergamodactylus.
  7. “Coronoid process that describes a posterodorsal concavity of the jaw reminds more of a lepidosaur than a maniraptor.” As in Bergamodactylus.
  8. “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:

  1. absence of an antorbital fenestra” AOF present in both
  2. “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.
  3. “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 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.

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.

Li Z, Wang W, Hu H, Wang M, Y H and Lu J 2020. Is Oculudentavis a bird or even archosaur? bioRxiv (preprint) doi:
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.

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