Pterosaur pycnofibres revisited: Yang et al. 2018

Yang et al. 2018 bring us a closer look
at pterosaur integumentary structures (= pycnofibres, pycnofibers) courtesy of Tom Kaye and his fluorescence technique,

From the abstract
These findings could imply that feathers had deep evolutionary origins in ancestral archosaurs, or that these structures arose independently in pterosaurs.”

The latter is true and has been known for years. 
Filament structures arose in the lepidosaur fenestrasaur ancestors of pterosaurs, including Cosesaurus, Sharovipteryx (Fig. 1) and Longisquama (Fig. 2). None of these are archosaurs. The archosaur hypothesis for pterosaur origins has failed to produce even one taxon with pterosaur synapomorphies that is not trumped by taxa first specified in Peters 2000 or more recently improved in the large reptile tree at ReptileEvolution.com, which includes pterosaur ancestors extending back to basal lepidosaurs, basal reptiles and Devonian tetrapods.

The problem is co-author Professor Michael Benton
doesn’t want pterosaurs to be derived from fenestrasaurs. The Yang et al. paper insisted that pterosaurs are archosaurs and members of the invalid Benton invented clade, Avemetatarsalia.

You might remember,
Professor Benton and Professor David Hone wrote a two-part set of papers (Hone and Benton 2007, 2009) that declared they would test two competing hypotheses of pterosaur origins Peters 2000 (fenestrasaurs) vs. Bennett 1996 (archosaurs). The second paper (2009) dropped all references to Peters 2000, deleting the taxa therein and falsely ascribed the now gutted hypothesis to Bennett 1996. Ultimately they were unable to find any ancestors for pterosaurs. That’s because they omitted them on purpose.

Figure 1. Sharovipteryx cervicals surrounded by filaments.

Figure 1. Sharovipteryx cervicals surrounded by filaments.

Why?
Benton (1999) declared tiny-fingered Scleromochlus was the nonviolent sister to pterosaurs and evidently Benton wanted to maintain that charade. That’s where he erected the invalid clade, Avemetatarsalia, which makes several appearances in Yang et al. 2018. Peters 2000 is not cited in Yang et al. 2018.

Longisquama in situ. See if you can find the sternal complex, scapula and coracoid before looking at figure 2 where they are highlighted.

Figure 2. Longisquama in situ. The bones are hard to see here due to filaments and skin, especially visible in the throat area.

True to S. Christopher Bennett’s curse,
“You will not get published and if you do get published you won’t be cited.” And that’s why I publish here, online, where I can respond immediately when something gets published that includes taxon exclusion. This is the dark underbelly of paleontology. Sorry that I had to show you this.

References
Bennett SC 1996. The phylogenetic position of the Pterosauria within the Archosauromorpha. Zoological Journal of the Linnean Society 118:261-308.
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 2009. Contrasting supertree and total evidence methods: the origin of the pterosaurs. Zitteliana B28:35–60.
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Yang et al. (8 co-authors including Benton MJ) 2018. Pterosaur integumentary structures with complefeather-like branching. Nature ecology & evolution

2 thoughts on “Pterosaur pycnofibres revisited: Yang et al. 2018

  1. I have no clue how, but you managed to overlook THE ONE BIG NEWS ITEM in the new paper: the pycnofibers are branched.

    This discovery makes it a lot more likely that pycnofibers are homologous to feathers than if they were just unbranched “hairs” of the general sort that we have, too.

    And yes, that’s evidence against your phylogenetic hypothesis on pterosaur origins – though I’ll be the first to admit that it’s just one character, so it’s not horribly strong evidence on its own.

    • Feathers on birds were both ontogenetically and phylogenetically shafts. And no one has yet described the filaments of Longisquama in detail. They may be fluffy, too, to say nothing about the suite of skeletal traits that link non-volant fenestrasaurs to volant fenestrasaurs (pterosaurs).

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