Sticking to their guns: Three paleontologists and their pet hypotheses

Paul Ellenberger 1974, 1978, 1993
described Middle Triassic Cosesaurus as a pre-bird. Other paleontologists understood birds arose from small feathered theropod dinosaurs by the Late Jurassic. So Ellenberger’s hypothesis was not accepted.

Twenty+ years later,
Dr. Ellenberger and I spent the day together at his home in Montpellier, a day after I examined his Cosesaurus in Barcelona. When I told him he actually discovered the long sought ancestor of pterosaurs (the one clade he did not test in his comparative anatomy studies), he dismissed the idea and refused any further discussion. He didn’t want to know, or even think about it. Perhaps Ellenberger kept his pet hypothesis to the grave. Don’t be like Dr. Ellenberger. Keep an open mind.

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 2000. A redescription of four prolacertiform genera and implications for pterosaur phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.

Mike Benton 1999
reported pterosaurs and tiny Scleromochlus, were closely related — and he wasn’t the first. A year later Peters 2000 introduced a phylogenetic series of four previously overlooked pterosaur ancestors and explained that Scleromochlus was a basal bipedal crocodylomorph with tiny hands, tiny fingers and no fifth toe.

A few years later,
Benton and his student, David Hone (2007-2008) undiscovered the origin of pterosaurs. After announcing a test of Peters 2000 in part one (2007) of their two-part study, Benton and Hone omitted Peters 2000 in part two (2009). Without the omitted data Benton and Hone were unable to recover one tenable pterosaur ancestor, let alone a phylogenetic series of ancestors. Using the supertree method, neither author had to examine any specimens. Their job was to cherry-pick previously published cladograms. For his part, Hone was awarded a PhD. For his part, Benton’s university textbook (2005, 2014), continues teaching students that Scleromochlus was a pterosaur and dinosaur ancestor.

More recently
Benton (see video on YouTube) closely examined pterosaur integumentary structures (= pycnofibers) and called them feathers… because they look like feathers. Don’t fall for this shortcut. We call this convergence. We call this “Pulling a Larry Martin.” Instead: be a good scientist. Run an analysis with a wider gamut of taxa. Find out if your subjects are indeed related to one another using hundreds of traits, not just one, two or a dozen. When you nurture and coddle an invalid pet hypothesis, you run the risk of having others shed light on your folly. Like Dr. Benton, any reputation you manage to build up over the decades will be undercut by your taxon omissions.

References
Benton MJ 1999. Scleromochlus taylori and the origin of dinosaurs and pterosaurs. Philosophical Transactions of the Royal Society London, Series B 354 1423-1446. Online pdf
Benton MJ 2005. Vertebrate Paleontology 3rd Edition PDF online Wiley-Blackwell 455 pp.
Benton MJ 2014. Vertebrate Paleontology 4th Edition Wiley-Blackwell 480 pp.
Hone DWE and Benton MJ 2007. An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465–469.
Hone DWE and Benton MJ 2008. Contrasting supertree and total evidence methods: the origin of the pterosaurs. Zitteliana B28:35–60.
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.

Kevin Padian 1985
and his friend Jacques Gauthier placed pterosaurs within the clade Ornithosuchidae along with Lagosuchus and the Dinosauria. These two young PhDs were riding a new wave of computer software in the earliest days of phylogenetic analysis. Back then (1985) they did not realize they were omitting pertinent taxa that would invalidate their hypothesis of interrelationships.

Thirty-five years later
Padian (2020) was still so attached to the similarities between pterosaurs and dinosaurs he wrote in support of Ezcurra et al. (2020), “Ezcurra et al. realized that, although lagerpetids didn’t fly, they share specific features with pterosaurs, such as … Their elongated hand (palm) bones (hyperelongated in pterosaurs, along with the fourth finger) suggest a good starting point for animals to evolve flight.” By contrast, Ezcurra et al. wrote, ” …lagerpetids, as with other archosauromorphs, _lack_ the enlargement of both the deltopectoral crest of the humerus and the fourth manual digit that characterizes pterosaur wings.”

Today
Kevin Padian is a highly regarded professor at a major university (UC Berkeley) and a champion of evolution. So it comes as a disappointment when he clings to a pet hypothesis that was invalidated by Peters 2000. Padian’s example shows this can happen to anybody at any level of education. Since this mistake was published in Nature this will be a stain on Padian’s curriculum vitae forever. Remember Kevin Padian when you have to make a similar decision against the evidence.

References
Gauthier JA and Padian K 1985. Phylogenetic, functional, and aerodynamic analyses of the origin of birds and their flight. In M. K. Hecht, J. H. Ostrom, G. Viohl, and P. Wellnhofer (eds.), The Beginnings of Birds: Proceedings of the International Archaeopteryx.
Padian K 2020. Closest relatives found for pterosaurs, the first flying vertebrates. Nature News and Views (2020).https://www.nature.com/articles/d41586-020-03420-z
Ezcurra MD et al. (17 co-authors) 2020. Enigmatic dinosaur precursors bridge the gap to the origin of Pterosauria. Nature (2020). https://doi.org/10.1038/s41586-020-3011-4

Consider these three academic examples as cautionary tales.
If you’re a scientist, don’t be caught supporting or promoting invalid hypotheses. If there is a competing hypothesis out there, test it and see if your pet hypothesis lives or dies. Don’t think about your status and reputation. Don’t think about the money. Don’t think about the potential for embarrassment. Do what is right, do what you profess, do science.

If you do discover something in paleontology,
like the origin of pterosaurs, expect crickets. In the 22 years since Peters 2000 no one has reached out to discuss their thoughts and arguments. Workers don’t want to know or even think about competing hypotheses. No one has improved on it, which is something I would welcome. Just don’t put your blinders on. Test all competing hypotheses. Figure this out for yourself.