LRT sheds light on Gastornis: its a giant flightless parrot!

I left adding extant birds to the LRT for last
because I thought the phylogeny of birds was already set in stone using extant bird DNA (Hackett et al. 2008; Prum et al. 2015). Now I’m learning that, once again, DNA does not replicate morphological analyses in birds over large phylogenetic differences.

I’m learning about post K-T birds step-by-step
as I meet them, one-by-one, as usual. Some surprises are popping up. Last time we looked at the giant bird Gastornis (Fig. 1, 6), it nested with the hoatzin, or stink bird, Opisthocomus. It still does so, but now we have an intervening transitional taxon, Ara macao, the scarlet macaw (Figs. 4, 5), a brilliantly colored parrot.

Figure 1. Gastornis turns out to be a giant parrot sister in the chicken clade in the LRT.

Figure 1. Gastornis turns out to be a giant parrot sister in the chicken clade in the LRT.

But first….
In the last few days I added two extant birds to the LRT. The common house sparrow, Passer domesticus (Linneaus 1758; Figs. 1,2) nests between the chicken, Gallus, and the hoatzin, Opisthocomus in the large reptile tree (LRT, 1065 taxa; subset Fig. 7). This counters DNA studies (Hackett et al. 2008; Prum et al. 2015) which nested Passer in a very derived node in a very derived clade with the long-legged snake-eater, Cariama, at its base.

Usually
highly derived taxa with atypical traits nest at derived nodes, not basal nodes. Passer is the dictionary definition of a very typical, not highly derived bird.

Figure 1. Skeleton of the common house sparrow, Passer domestics.

Figure 2. Skeleton of the common house sparrow, Passer domestics.

 

So far,
the chicken/Gallus clade is primarily composed of herbivores/ grain/ seed eaters with a few insects and lizards thrown in. Since Gastornis appeared in the late Paleocene/early Eocene, that means sparrows, chickens and hoatzins also must have been part of this earliest radiation of Neognathae after the K-T extinction event.

Figure 2. Skull of Passer domestics in four views.

Figure 3. Skull of Passer domestics in four views.

The scarlet macaw,
Ara macao (Linneaus 1758, Figs. 3, 4) nests between Opisthocomus, the hoatzin and Gastornis (formerly Diatryma, Fig. 1), the giant Eocene herbivore formerly considered a predator of little Eocene 3-toed horses. Gastornis shares a remarkably long list of odd bird traits with Ara, including the separation of its orbit from its temporal fenestrae (Fig. 5). Wikipedia reports Gastornis originally was allied with cranes, but recent studies nest Gastornis with geese. Neither are as good a match for Gastornis, from head to toe (and palate, Figs. 5, 6), as parrots using the LRT as our guide.

Figure 3. Skeleton of Ara macao, the scarlet macaw. Note the skeleton has pedal digits 3 and 4 switched.

Figure 4. Skeleton of Ara macao, the scarlet macaw. Note the skeleton has pedal digits 3 and 4 switched.

Most of the skull elements in Ara are fused,
but the mandible, palatine and quadrate rotate beneath the skull like a parallelogram to lift the beak. Witmer and Rose 1991 compared the skull of Gastornis ( = Diatryma) with that of the parrot Amazona in their study of jaw mechanics, without making the phylogenetic connection.

Witmer and Rose 1991 reported,
“The morphology of the last group, parrots and finches, is similar to that of Diatryma.” They all nest together in the LRT. They also report, “Although the craniofacial hinge is not completely preserved in any known specimen, we suggest that Diatryma, like large parrots, probably had a diarthrodial craniofacial articulation.”

Figure 4. Skull of Ara macao with bones colored.

Figure 5. Skull of Ara macao with bones colored.

The first reconstructed palate of Gastornis
(Fig. 6) compares well with that of Ara macao (Fig. 5), including the massive palatine bones, the long slender pterygoids, the wide jugals and indented quadratojugals.

Figure 5. The palate of Gastronis/Diatryma uncrushed to match the uncrushed mandibles. Note the clear resemblance to the palate of the parrot, Ara macao in figure 4.

Figure 6. GIF movie, 4 frames of the palate of Gastronis/Diatryma uncrushed to match the uncrushed mandibles. Note the clear resemblance to the palate of the parrot, Ara macao in figure 4.

I know a lot of time and treasure
have gone into past DNA studies, but they do not and can not include extinct taxa. They do not replicate tree topologies when the phylogenetic distances are great. So they do not and can not produce gradual accumulations of derived traits to help us learn about bird evolution. It just doesn’t work on so many levels! So let’s keep DNA studies restricted to smaller clade studies.

Figure 7. Subset of the LRT showing the nesting of Passer and Ara, newly added taxa.

Figure 7. Subset of the LRT showing the nesting of Passer and Ara, newly added taxa.

Odd nestings
occur with DNA studies when phylogenetic distances are great:

  1. The plant-eating hoatzin nests at the base of the raptorial eagles, vultures and owls
  2. Raptorial seriemas and falcons nest with seed-eating parrots and passerines
  3. The nearly identical secretary bird, Sagittarius, and seriema, Cariama, nest far apart

Reasonable nestings
occur in DNA studies when phylogenetic distance are not great.

  1. The chicken. Gallus, nests with the ostrich, Struthio, and the tinamou, Crypturellius.
  2. The loon, Gavia, nests with the penguin, Spheniscus.

And you’ll only know the phylogenetic distances are great
after morphological studies – with fossils.

References
Agnolin F 2007. Brontornis burmeisteri Moreno & Mercerat, un Anseriformes (Aves) gigante del Mioceno Medio de Patagonia, Argentina. Revista del Museo Argentino de Ciencias Naturales, n.s. 9, 15-25
Andors AV 1992. Reappraisal of the Eocene ground bird Diatryma (Aves: Anserimorphae). Science Series Natural History Museum of Los Angeles County. 36: 109–125.
Hackett S et al. 2008. A phylogenetic study of birds reveals their evolutionary history. Science 320:1763–1768.
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
Mustoe GE, Tucker DS and Kemplin KL 2012. Giant Eocene bird footprints from northwest Washington, USA. Palaeontology. 55 (6): 1293–1305.
Prum RO et al. (6 co-authors) 2015. A comprehensive phylogeny of birds (Aves) using targeted next-generation DNA sequencing. Nature doi:10.1038/nature15697
Witmer L and Rose K 1991. Biomechanics of the jaw apparatus of the gigantic Eocene bird Diatryma: Implications for diet and mode of life. Paleobiology. 17 (2): 95–120.

wiki/Gastornis
wiki/Sparrow
wiki/Scarlet_macaw

Click here for a video of a hatching and growing Hyacinth Macaw from Andy Hoo. Excellent. 100 days to fledge.
Reminds us that dinos are naked, not scaly. And they need parents to survive.

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