Padian 2024
celebrated the 50th anniiversary of John Ostrom’s publication(s) of 1974a, b, c that focused on the then contentious ancestry of birds. In hindsight, the ancestry of birds seems obvious (Fig 1), but that was then. That was fifty years ago. It was even obvious to Huxley 1868 after seeing Archaeopteryx and Compsognathus. Paleontology, as a science, moves at a snail’s pace.
Professor Ostrom was Padian’s PhD advisor when he attended Yale University.
Specifically Padian focused on,
“A landmark 1974 paper [Ostrom 1974a] reset the debate to focus on the evolution of the flight stroke instead.”
You’ll notice, as you age and gain experience,
that paleontologists like to talk about and write about ‘the old days’ when speculation ran wild. And about minutia, like the flight stroke. They do this rather than putting effort into building cladograms that consider all candidates, that nest all enigmas and resolve all taxonomic issues.
Instead, paleontologists too often set up a ‘strawman‘. Here’s one example:
See if you can spot the key omission as Padian sets up his own straw man,
“Birds had to have come from forerunners, which had always been assumed to be reptiles rather than mammals. But the fossil record was incomplete between some major adaptive transitions (such as from ground- or tree-dwelling reptiles to flying birds), and potentially ancestral fossil reptile groups always seemed to have some but not all of the expected ancestral features, or to have them in the wrong combinations.”
Did you think of any of the dozen or so Solnhofen birds (= Archaeopteryx, Fig 1) that somehow were overlooked in this paragraph? Overlooking the obvious is, unfortunately, all too common in paleontology. Taxon exclusion is also pervasive. When Padian wrote, ‘the fossil record was incomplete,’ he was ignoring the transitional taxa that linked birds to theropods ever since Huxley 1868, This is what they do: ‘setting up a straw man.’
Figure 1. Known from over a century prior to Sinosauropteryx, Early Jurassic, apparently the feathers of this specimen of Archaeopteryx were not sufficient evidence for feathers on dinosaurs according to Padian and other workers. This is the sort of attitude you can expect to fight against if you decide to enter the science of paleontology.
re: ‘the old days’ Padian wrote,
“The default hypothesis was that birds evolved from a poorly defined group of creatures called thecodonts (a ragtag bunch related variably to crocodiles or dinosaurs), from a crocodile lineage or possibly from dinosaurs (ornithischians or saurischians).”
Again, omitting the obvious: Archaeopteryx (Fig 1).
Figure 2. Ostrom’s insect-net hypothesis illustrated. This was not well received, according to Padian 2024.
Ostrom envisioned an insect trap
for the origin of larger and larger manus feathers on small theropod dinosaurs (Fig 2). As Padian noted, “Ostrom’s ‘insect net’ hypothesis was not well received.” largely because birds don’t do that with their wings and feathers.
Padian mentioned Dial’s 2003 work
with juvenile birds running up tree trunks. That study was widely accepted because it dealt with small prevolant birds (aka juvenile theropod dinosaurs) using their feathers and rapid flapping to survive and thrive.
Padian 2024 concluded,
“This {Dial’s studies of prevolant birds] unquestionably shows a crucial early adaptation of feathers, and rules out the idea that proto-birds must have climbed trees using their hand claws. But the problem has never really been ground up versus trees down: it has been about the evolution of the flight stroke, which can now be seen as having helped proto-birds to escape from terrestrial predators. Ostrom reset this debate in 1974, and its
implications continue to resound.”
Padian still has great affection and respect for his PhD advisor. We all do. But the flight stroke of birds never involved an attempt at netting insects in front of the rostrum (Fig 2). It didn’t happen because it can’t happen. Padian’s celebration of the Ostrom 1974 paper that promoted this hypothesis is not a great idea. Worse yet for the spin Padian put on it. Creationists jumped all over Padian’s sincere, but ill-considered homage.
It is no surprise that Ostrom’s illustration (Fig 2) did not appear in Padian’s 2024 homage. Dial’s illustration of running, flapping pre-volant birds appeared instead.
In 1975 Ostrom reported,
“dinosaurs were not like modern reptiles.” In this statement Ostrom was focused on the endothermy vs. endothermy debate. Ostrom’s work at that time argued for the possibility of dinosaur endothermy. His opponent in this debate, Feduccia 1973, argued against that possibility.
Ostrom 1974c wrote,
“He [Feducia] continues with the true, but totally irrelevant conclusion that the converse argument does not hold-Le., that animals which do not have erect posture should not
be capable of muscular thermogenesis sufficient to maintain an endothermic regulatory system, and he cites such endothermic “sprawlers” as cetaceans, pinnepeds, dugong, echidna, moles and the brooding python. Of course an endotherm may be adapted for a sprawling existence with non-erect posture.”
This was the core of the birds are dinosaurs debate back then, not the flight stroke, which was a bit of a detour, perhaps more important to Padian than to Ostrom.
Ostrom 1974c continued,
“The critical question that Feduccia carefully avoids in his 1973 paper is – can erect posture be achieved by an ectotherm? or is the variable, externally affected physiology of an ectotherm so unstable and incapable of long-term sustained activity that the transition from a sprawling to an erect carriage cannot be achieved? In his present paper (1974), even Feduccia claims that endothermy preceded erect posture in mammals. It is not clear to me why this same sequence cannot be true of dinosaurs also.”
Well said, Dr Ostrom.
To Padian’s point:
Now we know the origin of the flight stroke in birds and pterosaurs arises from a locked down, elongate set of coracoids. In bats a locked down, elongate set of clavicles serves the same purpose: raising the pectoral limbs and ensuring they move symmetrically – the opposite of traditional tetrapod pectoral limb movement. This innovation (flapping prior to flying for various reasons) seems to be overlooked by most workers, but embraced by Dial’s studies. You’ll see more gliding Archaeopteryx videos than flapping videos.
All this gets us back to the origin of turtles, whales, bats and pterosaurs.
Ostrom 1974c wrote, “Divergent interpretations should be debated, for it is by this means that we have the best hope of approximating the truth-especially when the question at issue is beyond proof.”
With that in mind, and inspired by Padian 2024,
I wrote to Chris Bennett and Kevin Padian via email, hoping for a kumbaya moment. Here is the body of the text:
“Decades ago, at one of the first pterosaur symposia, I remember you two insisting that phylogenetic analysis was the key to understanding taxonomic interrelationships. That was just a few years after the introduction of software (MacClade and PAUP) to make that happen in a repeatable and testable manner. It was a ‘hot topic’ back then.
“In one of my first papers (Peters 2000) I added taxa to three earlier studies. You might remember that results pulled pterosaurs away from archosaurs and dinosaurs and towards the newly added taxa: Sharovipteryx, Longisquama, Cosesaurus, Langobardisaurus and the tanystropheids (which share nearly identical feet with that odd metapodial fifth toe, among a long list of other traits). Apparently no one saw that coming and no one ‘believes’ it to this day.
“Even so, and since then, adding taxa to a growing online cladogram, the large reptile tree (LRT, 2300+ taxa) at ReptileEvolution.com has clarified interrelationships in taxa from Cambrian fish to bats and whales.
“Thank you for guidance and insistence. The process of discovery has been fascinating.
“This note to you both was inspired by Kevin’s recent Nature article on the 50th anniversary of Ostrom 1974.
“According to the Hartford Courant (2000), “In 1973, Ostrom broke from the scientific mainstream by reviving a Victorian-era hypothesis (see above) that his colleagues considered far-fetched: Birds, he said, evolved from dinosaurs. And he spent the rest of his career trying to prove it.” With the announcement of the first dinosaurs with feathers from China, Ostrom (then age 73) was in no mood to celebrate. He is quoted as saying, ““I’ve been saying the same damn thing since 1973, `I said, `Look at Archaeopteryx!’” Ostrom was the first scientist to collect physical evidence for the theory. Ostrom provoked a debate that raged for decades. “At first they said, `Oh John, you’re crazy,”’ Ostrom said in 1999.”
“The fact that Ostrom’s ‘far-fetched’ idea took awhile to percolate into the minds of his colleagues continues to give me hope that someday the same will be confirmed, refuted or modified for pterosaur origins. In other words, I will be happy if someone finds a closer relationship to taxa other than those listed above – if they examine the fossils firsthand and run analyses, as you two insisted I do so many years ago.
“Thank you, again, and best regards,”
It’s been several days. I’ll let you know what they each say when they write back
– if they ever reply.
References
Dial KP 2003. Wing-assisted incline running and the evolution of flight. Science 299, 402–404.
Feuccia A 1973. Dinosaurs as reptiles. Evolution 27:166–169.
Heers AM, Baier DB, Jackson BE and Dial KP 2016. Flapping before Flight: High Resolution, Three-Dimensional Skeletal Kinematics of Wings and Legs during Avian Development. PLoS ONE 11(4): e0153446. doi:10.1371/journal.pone.0153446
http: // journals.plos.org/plosone/article?id=10.1371/journal.pone.0153446
Huxley TH 1868. On the Animals which are most nearly intermediate between Birds and the Reptiles. Annals and Magazine of Natural History 4(2): 66-75.
Ostrom JH 1969. Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana. Bulletin of the Peabody Museum of Natural History. 30.
Ostrom JH 1970. Stratigraphy and paleontology of the Cloverly Formation (Lower Cretaceous) of the Bighorn Basin area, Wyoming and Montana. Bulletin of the Peabody Museum of Natural History. 35: 1–234.
Ostrom JH 1973. The ancestry of birds. Nature 242: 136.
Ostrom JH 1974a. Archaeopteryx and the origin of flight. Quarterly Review of Biology 49:27–47.
Ostrom JH 1974b. On the origin of Archaeopteryx and the ancestry of birds. Proceedings of the Cent. Nat. Recherche Sci.
Ostrom JH 1974c. Reply to Dinosaurs as reptiles. Evolution27 (1): 166-169.
Ostrom JH 1975. The Origin of Birds. Annual Review of Earth and Planetary Sciences. 3 (1): 55–77.
Ostrom JH 1976. Archaeopteryx and the origin of birds. Biological Journal of the Linnean Society. 8 (2): 91–182.
Padian K and Chiappe LM 1998. The origin of birds and their flight. Scientific American 278(2):38–47.
Padian K 2023. 25th anniversary of the first known feathered dinosaurs. Nature (News and Views) 613, 251-252. doi: https://doi.org/10.1038/d41586-022-04586-4
Padian K 2024. 50 years after a landmark paper on bird-flight origins. Nature 627:738–740.
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