New paper on oldest bats cherry-picks the wrong outgroup taxa

Rietbergen et al 2023 reported,
“Here, we describe a new species of Icaronycteris based on two articulated skeletons discovered in the American Fossil Quarry northwest of Kemmerer, Wyoming. The relative stratigraphic position of these fossils indicates that they are the oldest bat skeletons recovered to date anywhere in the world.”

Remember: ‘oldest’ does not mean ‘most primitive.’

Figure 1. Icaronycteris gunnelli (ROM:Palaeobiology-Vertebrate Fossils:52666). One of the oldest bat fossils in the world.

We’ve seen this fossil before.
I based my drawing of Icaronycteris for ReptileEvolution.com on it in 2015 (Fig 2).

Figure 2. Icaronycteris reconstruction from several years ago based on the fossil in figure 1.

Not sure why bat experts continue to do this, but
the authors of this paper cherry-picked two bat outgroup taxa not related to bats: Erinaceus, the hedgehog, and Sorex, the shrew. This is a university tradition that needs to go away.

Whale experts do this, too, nesting extinct deer, cattle and pigs basal to whales and odontocetes basal to mysticetes.

Pterosaur experts do this, too, nesting phytosaurs, Euparkeria, Lagerpeton and/or Scleromochlus as outgroup taxa… anything to avoid considering Cosesaurus.

By contrast,
the large reptile tree (LRT, 2306 taxa, subset Fig 3) documents bat outgroup taxa back to Cambrian worms. The LRT nests the tiny ‘primate’ Microcebus at the base of the Chiroptera (the bat clade). Strangely, there was no mention of extant Tadarida in the text of Rietbergen et al 2023, nor does it appear in their cladogram.

BTW: The Green River bat 2022 in the LRT (Fig 3) is still unpublished.

Figure 3. Subset of the LRT focusing on bats and their ancestor, Microcebus, a mouse lemur.

Taxon exclusion continues at the end of 2023
as the number one problem facing paleontology. Never cherry-pick your outgroup taxa. Always let your wide-gamut cladogram pick for you. This is something you should be hearing from a PhD professor, not a home-schooled amateur blogger.

References
Rietbergen TB, van den Hoek Ostende LW, Aase A, Jones MF, Medeiros ED, Simmons NB 2023. The oldest known bat skeletons and their implications for Eocene chiropteran diversification. PLoS ONE 18(4): e0283505. https://doi.org/10.1371/journal.pone.0283505

reptileevolution.com/icaronycteris
wiki/Icaronycteris