Naish, Witton and Martin-Silverstone 2021 team up
to promote just about every pterosaur myth out there. Roll up your sleeves if you want to continue through this mucky paper. Longtime readers will be familiar with the usual issues.
From the abstract:
“Competing views exist on the behaviour and lifestyle of pterosaurs during the earliest phases of life. A ‘flap-early’ model proposes that hatchlings were capable of independent life and flapping flight, a ‘fly-late’ model posits that juveniles were not flight capable until 50% of adult size, and a ‘glide-early’ model requires that young juveniles were flight-capable but only able to glide.”
Competing views? 1) There is no view that hatchlings were able to glide without flapping. Flapping precedes flight in pterosaur precursors. due to a locked-down, elongate coracoid. 2) The authors omit tiny adult pterosaurs with fly-sized hatchlings (Fig. 8). Tiny pterosaurs had to wait to fly due to surface area-to-volume constraints that would result in desiccation whenever removed from a damp leaf litter environment, as in extant tiny lizards. Four pterodactyloid-grade clades had their genesis with phylogenetic miniaturization.
“We argue that a young Sinopterus specimen has been mischaracterised as a distinct taxon.”
They are talking about Nemicolopterus, which is a tiny pterosaur more closely related to Shenzhoupterus (Fig. 1). There is no phylogenetic context in this paper. Shenzhoupterus is not mentioned in text.
Naish et al. continue,
“We further show that young juveniles were excellent gliders, albeit not reliant on specialist gliding.”
No. Not reliant. Gliding evolves after flapping in taxa capable of both.
“The wing forms of very young juveniles differ significantly from larger individuals, meaning that variation in speed, manoeuvrability, take-off angle and so on was present across a species as it matured.”
This is false. Late-stage embryos and hatchlings had adult proportions (Figs. 1, 3, 4, 8, 9).
See if you can find the internal conflict in these two abbreviated sentences
from the Naish et al. introduction. 1) “very young pterosaurs can be identified on the basis of both skeletal proportions and… osteological immaturity. 2) Even embryonic pterosaurs were well-ossified and adult-like in skeletal proportions.”
See if you can find the internal conflict in this sentence:
“Overall, their development recalls that of precocial sauropsids rather than the altricial offspring of neoavian birds.” (Hint: birds are traditional sauropsids, an invalid taxon not recovered by the LRT).
Naish et al. cite other authors who mix up phylogeny with ontogeny
Naish et al. cite authors who mix up early embryos with full-term embryos.
Naish et al. wander into an imaginary scenario
when they report, “It could be argued that a late development of flight in pterosaurs is consistent with the fact that the majority of extant volant vertebrates are incapable of flight in early life.” Stay with the evidence. Don’t wander.
Naish et al. have no idea what pterosaurs are.
Pterosaur egg shells are lizard-like because pterosaurs are lepidosaurs. The authors eschew a phylogenetic context. The keyword, “lepidosaur” does not appear in their text.
Throwing phylogeny out of the window,
the authors cite “Hone et al. [who] showed how skeletal proportions present across the ontogeny of Rhamphorhynchus are indicative of precociality and adult-like flight behaviour in hatchlings.” Hone et al. mixed phylogenetically miniaturized taxa with larger, later taxa. Whatever happened to ‘adult proportions’? Naish either want to have it both ways and hope nobody notices, or they don’t want to upset their firend. I don’t see any critical thinking or editing in this paper.
See if you can find the internal conflict in this sentence:
“Firstly, we modelled the gliding ability of hatchlings to assess whether their wing skeletons were sufficiently developed to support flight.” Gliding (like some squirrels) and flying (like birds and bats) should not be discussed in the same sentence. Those taxa able to glide and fly always flap first, glide later.
this paper is a prime example of looking for details when the overall setting is wrong to begin with. In other words, this paper is like trying to straighten a picture hanging on the wall while the whole house is being rapidly swept downstream in raging flood waters. The authors do not understand what pterosaur is before trying to understanding what their hatchlings were capable of. A valid phylogenetic context is needed here.
At this point, Naish et al. argue for the youth of Nemicolopterus.
Indeed, Nemicolopterus is much smaller than related taxa (Fig. 1). Phylogenetic analysis in the large pterosaur tree (LPT) nests Nemicolopterus with Shenzhoupterus, an adult taxon and possible parent. Shenzhoupterus is not mentioned by Naish et al. Instead they decide (without a cladogram) that Nemicolopterus is a juvenile Sinopterus… AND that various larger Sinopterus and Huaxiapterus taxa represent more mature specimens of a single species. When you play such phylogenetic games, making up relatives as you please, the concept of hard science has clearly left the building.
Remember when Naish et al. said hatchlings had adult proportions?
Here (Fig. 1) they forgot they said that. They double down in their caption, which reads, “Note progressive change in skull shape and exaggeration of cranial crest in larger specimens, a feature consistent with cranial growth in other pterosaur species.”
At this point it is probably appropriate to remind readers
that hatchings and juveniles had adult proportions. See Pterodaustro (Fig. 3) and Zhejiangopterus (Fig. 4) for documentation of these examples.
At this point Naish et al. break out
their precise measurements and calculations and finish with a chart of gliding tetrapods, all adults other than the ‘hatchling pterosaurs’. No where on this chart do they include birds or bats. Nor do they include adult pterosaurs. We call that, “taxon exclusion.”
Naish et al. report,
“Our gliding calculations emphasise differences between gliding animals and hatchling pterosaurs, and thus raise the possibility that hatchlings were powered fliers.” No where do Naish et al spell out the single trait shared by powered fliers: an elongate, locked down coracoid (or clavicle in the case of bats). Gliders that never had powered flyer ancestors, lack this trait.
Naish et al. report,
“The robustness of pterosaur humeri has been linked to the demands of forelimb-assisted launch, and the exceptionally high humeral bending strengths of hatchlings leaves little doubt about launch capacity.”
We covered the extreme danger of the hypothetical and invalid forelimb-assisted launch earlier here (Fig. 6), along with the morphological errors (Fig. 7) ignored by its creator, Michael Habib and embraced by Naish, Witton and Martin-Silverstone.
Some things are difficult if not impossible for Naish et al. as they report,
“It is difficult if not impossible to state precisely when hatchling pterosaurs began to fly given that presently unknowable factors—possible parenting behaviours, hatchling coordination, last-minute soft-tissue development, the nature of nesting environments and so on—likely influenced this, as they do in living megapodes.”
Sadly, these three pterosaur experts do not attempt a reconstruction of the IVPP embryo (Fig. 8), or the JZMP embryo (Fig. 9) or cite those who have done this already. These embryos were definitely ready to fly without the need for ‘last minute soft-tissue development.’
Over and over Naish et al. 2021 give the impression
that they don’t like to include more taxa, that they don’t like cladograms, that they don’t like tracing bones (their caption 2 confesses, “Skulls redrawn from the literature”), that they are often 15 years behind the times when they embrace then deny the fact that pterosaur hatchlings and embryos are identical to their parents (Figs. 3, 4).
When Naish et al. 2021 report,
“Our results are further evidence of pterosaur hatchlings being highly precocial and potentially capable of living independently of their parents.” It’s okay if you’re not excited. We’ve known this for 16 years.
Naish et al. report their thoughts on parenting,
when they have no evidence for it, or against it. They just wander through it. With a valid phylogenetic context, they could have said, “The hatchlings of the tuatara receive no parental care and have to fend for themselves.” They could also have said, “As in other lepidosaurs, pterosaur mothers retained her pterosaur egg(s) within her uterus until ready for hatching.” That explains the Hamipterus assemblage where empty eggs and skeletons were found swept together after asphyxiation during pregnancy and later decay.
Naish et al. report,
“With reduced flight speeds and lesser glide performance (Table 2), hatchling Sinopterus and Pterodaustro would not have been as efficient as their parents at long-distance travel.”
They ignore the simple fact that relative distances for tiny hatchlings are 8x greater AND hatchlings have proportionally smaller body stores. Moving deeper into conjecture, the authors report, “these attributes might have rendered juvenile pterosaurs more dynamic fliers than their parents, better able to switch between aerial and terrestrial locomotion, better suited to executing sudden changes in direction and velocity, and capable of nimbler flight in complex environments.”
No comparisons can be made with arctic terns, who raise altricious plover-like hatchlings for several weeks before fledging. But shortly after doing so, young terns are able to migrate from pole to pole twice a year.
Naish et al. report,
“The changes in wing form that pterosaurs underwent during growth might not be viewed as strictly adaptive because much of their effect on flight reflect unavoidable laws of scaling.”
This is false and contradicts earlier text. As shown above (Figs. 3, 4, 8, 9), pterosaur embryos and hatchlings all have adult proportions from skull to wing form and elsewhere. Only the size changes.
Naish et al. report the obvious,
“many pterosaurs were large animals with small offspring, creating large intraspecific size ranges and the potential for multiple potential niches.”
All adult pterosaurs are 8x larger from available data. You bet they are going to go after different prey.
Naish et al. confess:
“We stress that the concepts outlined here are hypothetical.” Usually Nature doesn’t get into such hypothetical studies, preferring instead to document new exciting fossil discoveries that break new ground. As you can see, it’s not always good to have friends who support your ideas. Chris Bennett is still out there. He is listed as one of those who provided “comments that improved the manuscript substantially.”
With all the above disregard for morphology and phylogeny by Naish et al.,
you might ask yourself, why was this paper published in Nature? Answer: The authors have academic friends who are editors and referees who like what they are saying, just like any other paper. That doesn’t mean they are correct. Nature has published a long list of paleo mistakes all listed and chronicled here, only a few of which they have owned up to.
Congratulations to Naish, Witton and Martin-Silverstone
Nature has never published such a raft of conjecture, fantasy and misinformation.
Naish D, Witton MP and Martin-Silverstone E 2021. Powered flight in hatchling pterosaurs: evidence from wing form and bone strength. Sci Rep 11, 13130 (2021). https://doi.org/10.1038/s41598-021-92499-z
ResearchGate.org: First juvenile Rhamphorhynchus
This just in
from Tetzoo.com, Darren Naish’s website. “The novelty of our study, is that we use specific tests to better establish these models [pterosaur superprecociality or ontogenetic niche partitioning] over others that have been presented, and that we propose more finely honed ideas on the ways in which hatchlings and young juveniles might have differed from older juveniles and adults.”
Naish also provides “a ridiculous backstory.” According to him the project has been on the burner since 2008. Naish writes, “The problem with doing science in your ‘spare time’ (neither myself, Mark or Liz are salaried research scientists: any scientific writing or research we do happens in ‘spare time’), is that it’s very hard to find time to do things like deal with the rewrites and new tests demanded by peer review.” So there you have it, a little insight into the process.