Palaeoglaux: Headless Eocene owl? or coot?

Today’s post
had its genesis in a blogpost at Synapsida, “Before owls ate mice.” Synapsida is a site about paleontology who reported on the two Eocene bird specimens discussed below. One is more owl-like than the other, but both were reported to be and accepted as owls.

DS Peters (no relation) 1992
described a new species of owl from the Eocene Messel oil shale. Palaeoglaux artophoron (Fig. 1) was small, headless, has a “pnuematic coracoideum“, a “narrow proximal end of the ulna”, has “peculiar feathers”, “the osseous arch of the radius seems to be a unique character for owls” and “displays a mixture of tytonid and strigid characters.”

in the large reptile tree (LRT 1821+ taxa) Palaeoglaux does not nest with owls, but with Fulica, the coot (Fig. 2) and a skull-only coot sister, Asterornis from the Cretaceous. Based on just the headless but otherise relatively complete and articulated post-crania, only five extra steps are needed to move Palaeoglaux to the owls. Note the distinctly different toe 4 length (Fig. 1) in Palaeoglaux compared to owls. The rest of the differences are more subtle.

Palaeoglaux artophoron (Eocene) in situ above, feet reconstructed below. Colors and scale bars added here along with feet from two owls, Primoptynx (Eocene) and Bubo (extant). Note the tail feathers at lower right.
Figure 1. Palaeoglaux artophoron (Eocene) in situ above, feet reconstructed below. Colors and scale bars added here along with feet from two owls, Primoptynx (Eocene) and Bubo (extant). Note the tail feathers at lower right.

The feathers on the trunk
are only 1mm wide and 2cm long, without barbs. Such feathers are typically found in birds that display bright colors during daylight, but owls are nocturnal, so DS Peters 1992 wondered if this was an exceptional diurnal owl.

Synapsida at write:
“To understand the origin of owls, then, it’s helpful to look at these even older species, some of which date back to not long after the extinction of the non-avian dinosaurs.”

Figure 2. The coot, Fulica, nests with Palaeoglaux in the LRT. The coot has longer cervicals, smaller wings, and more gracile feet than Palaeoglaux.

That’s one way to do it.
The other way is to drop taxa into a phylogenetic analysis to see which taxa are last common ancestors with this new taxon. In other words, broaden the range of possibilities to let the software decide. Bird expert DS Peters, now 89, knew he had an owl from the start based on my reading of the text of his paper. He saw owl characters and odd characters in his specimen.

Figure 3. Bubo the extant owl compared to Primoptynx, the Early Eocene owl. See figure 1 for pedal closeups. Note the brevity of pedal 4.

Synapsida and DS Peters 1992 note
that Palaeoglaux is the exception to the rule that other earliest owls are represented by just a bone or two. Synapsida also reports on Primoptynx poliotaurus (Mayr, Gingerich and Smith 2020; Figs. 1, 3) an owl from the Greybull formation (Early Eocene), 55 mya, with beak, vertebrae, sternum, wing and both legs. “The ungual phalanges of the hallux and the second toe of the new species are distinctly larger than those of the other toes. Current data do not allow an unambiguous phylogenetic placement. Concerning the size of the ungual phalanges, the feet of P. poliotauros correspond to those of extant hawks and allies (Accipitridae). We therefore hypothesize that it used its feet to dispatch prey items in a hawk-like manner, whereas extant owls kill prey with their beak.”

The Synapsida author presented a cladogram
based on a genomic test by Jarvis et al. 2014 that nested owls with kingfishers + woodpeckers, further on with hawks and condors, then with falcons + parrots + songbirds. The LRT does not confirm a relationship of owls with kingfishers or either with woodpeckers, nor a relationship between falcons and parrots, as proposed earlier by Mayr 2011. We know better not to trust genomic tests. Too many false positives recovered with DNA and other gene studies in deep time subjects. Epigenetics must be changing the genomes because so many clades become geographic.

In the LRT about half the scored traits are cranial, so lacking a cranium and jaws is a real handicap. Even so, the LRT, by virtue of testing a wider gamut of taxa, was able to lump and separate taxa that were not previously considered.

Too many science bloggers,
from Synapsida, to Nat Geo, Scientific American, the Guardian, and others do not use their scientific know-how to test the claims of workers. Instead they simply disseminate, repeating without questioning. Let’s start testing and questioning published claims.

Jarvis ED et al. (several dozen co-authors) 2014. Whole-genome analyses resolve early branches in the tree of life of modern birds. Science 346(6215):1320–1331.
Mayr G, Gingerich PD and Smith T 2020. Skeleton of a new owl from the early Eocene of North America (Aves, Strigiformes) with an accipitrid-like foot morphology. Journal of Vertebrate Paleontology 40(2): e1769116
Mayr G 2000a. A new raptor-like bird from the Lower Eocene of North America and Europe. Senckenbergiana lethaea 80:59–65.
Mayr G 2005. The postcranial osteology and phylogenetic position of the Middle Eocene Messelastur gratulator Peters, 1994—a morphological link between owls (Strigiformes) and falconiform birds? Journal of Vertebrate Paleontology 25(3):635–645.
Mayr G 2011. Well-preserved new skeleton of the Middle Eocene Messelastur substantiates sister group relationship between Messelasturidae and Halcyornithidae (Aves, ? Pan-Psittaciformes). Journal of Systematic Palaeontology 9(1):159-171.
Peters DS 1992. A new species of owl (Aves: Strigiformes) from the Middle Eocene Messel oil shales. In Papers in Avian Paleontology Honoring Pierce Brodkorb. edited by Kenneth Campbell, Jr. NO. 36 Science Series. Natural History Museum of Los Angeles County, Science series No 36: 161-169.
Peters DS 1994. Messelastur gratulator n. gen. n. spec., ein Greifvogel aus der Grube Messel (Aves: Accipitridae). Courier Forschungsinstitut Senckenberg 170:3–9.


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