Cyrilavis colburnorum: a mouse bird, not a stem parrot

Updated December 19, 2021 with a revision to the LRT due to adding taxa

While researching fossil parrots,
in preparation for tomorrow’s post on a giant parrot, I found a paper by Ksepka, Clarke and Grande 2011 describing a Green River “stem parrot.” Cyrilavis colburnorum (early Eocene, Fig. 1), turns out to be a primitive mouse bird, very similar to the extant Urocolius (Fig. 2)  Convergent with two tested barbets, the posterior maxilla extends lateral to and below the jawline and terminates without narrowing to a point or suturing to other bones.

FIgure 1. Skeleton of Cyrilavis in situ. This is not a parrot, but a barbet from the Green River formation.

FIgure 1. Skeleton of Cyrilavis in situ. This is not a parrot, but a barbet from the Green River formation.

Originally the skull was crudely traced
with an outline that failed to identify several bones and misidentified others.

The Ksepka team also failed to include
barbets in their phylogenetic analysis. Only parrots and the outgroups passeriformes, falconidae, and mouse birds in order of increasing distance.

Figure 1. Urocolius, the blue-napes mousebird, converges with parrots in having a reversible toe 4, the ability to feed upside-down and having a short, deep, hooked beak...plus that long parrot-like tail!

Figure 2. Urocolius, the blue-napes mousebird, converges with parrots in having a reversible toe 4, the ability to feed upside-down and having a short, deep, hooked beak…plus that long parrot-like tail!

Like parrots,
and barbets, mouse birds sometimes have a zygodactyl (pedal digit 4 oriented posteriorly) pes (Fig. 5).

The authors discuss the clade, Halcyornithidae,
a clade within Pan-Psittaciformes. The authors report, “All character states potentially supporting halcyornithid monophyly are reconstructed as ambiguous synapomorphies due to the unresolved polytomy containing the five sampled taxa.” 

References
Feduccia A and Martin LD 1976. The Eocene zygodactyl birds of North America (Aves: Piciformes). Smithsonian Contributions to Paleontology, 27:101–110.
Ksepka DK, Clarke JA, and Grande L 2011. Stem parrots (Aves, Halcyornithidae) from the Green River Formation and a combined phylogeny of Pan-Psittaciformes. Journal of Paleontology 85:835-854

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