Eocene swift: Parargornis

Earlier we looked at
Eocypselus, an Eocene bird taxon originally considered basal to hummingbirds and swifts. The large reptile tree (LRT, 1205 taxa) nested Eocypselus with the hummingbird, Archilochus, far from the swift, Apus, which nested with falcons, owls and other hook-beaked predatory birds.

Today we look at
Parargornis (Mayr 2003; Eocene; Figs. 1–3), which nests with Apus in the LRT, far from hummingbirds and far from Eocypselus.

Figure 1. Parargornis fossil from the Messel pits in various views.

Figure 1. Parargornis fossil from the Messel pits in various views.

Mayr 2003 reported,
“Most recent authors consider the Trochilidae (hummingbirds) to be the closest extant relatives of swifts and both taxa are usually united in a single order Apodiformes (e.g. del Hoyo et al. 1999). Monophyly of swifts and hummingbirds is not only supported by derived morphological characters, but also by biochemical and molecular analyses (Kitto & Wilson 1966; Cracraft 1981; Sibley & Ahlquist 1990; Johansson et al. 2001; Mayr 2002). A recent phylogenetic analysis by Mayr (2002) provided strong evidence that the Aegothelidae (owlet nightjars) are the sister taxon of the Apodiformes.”

One of the reasons
why owlet nightjars nest close to swifts is because owls nest close to swifts in the LRT. Owlets appear to be (but have not yet been tested) transitional taxa linking owls to swifts. The hook bill of all predatory birds is not like the long straight bill of hummingbirds, which the LRT nests with certain sea gulls, far from swifts, among tested taxa.

Figure 2. Parargornis forelimb and hindlimb. One toe is broken and reconstructed here.

Figure 2. Parargornis forelimb and hindlimb. Toe two is broken and reconstructed here. Look for the ungual on top of distal metatarsal 2, courtesy of DGS.

Feathers were found with Parargornis
(Fig. 3) and more appear to be buried in the matrix forming an indistinct halo around the skeleton.

Figure 4. Parargornis feathers and feather halo.

Figure 3. Parargornis feathers and feather halo.

References
Mayr G 2003. A new Eocene swift-like birds with a peculiar feathering. Ibis 145:382–391.

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