Bird cladogram 2018 and the origin of penguins

Bird interrelationships
are coming together (Fig. 1). Here, wrens, dippers and woodpeckers now nest with crows, jays and grackles. Little else has changed. A few more taxa were also added.

Figure 1. Subset of the LRT focusing on birds. Here various aspects of birds are shown, including age, teeth, feeding behavior and basic clades.

Figure 1. Subset of the LRT focusing on birds. Here various aspects of birds are shown, including age, teeth, feeding behavior and basic clades. Four images change every 5 seconds.

The interesting thing I find in this cladogram
(Fig. 1) from the large reptile tree (LRT, 1146 taxa) is the highly derived placement of the penguin Aptenodytes. That’s really to be expected. However, a basal penguin, Waimanu (Slack et al. 2006; Fig. 2) nests from the Middle Paleocene (61.6 mya), soon after the K-T extinction event. That’s not really expected if one follows traditional cladograms that have birds radiating quickly and widely from the K-T boundary on out. Or maybe they did!

Figure 2. Waimanu is the penguin ancestor from the Middle Paleocene.

Figure 2. Waimanu is the penguin ancestor from the Middle Paleocene.

Wikipedia reports,
“Both DNA sequence analyses and anatomy argue for a close relationship between penguins and loons, with penguins being specialized for wing-propelled diving, and loons for foot-propelled diving.” Slack et al. 2006 nest penguins with storks, loons an petrels in order of increasing distance. I don’t see kingfishers in that list. And I wonder which stork was tested, because the Jabiru (see below) is traditionally considered a stork.

Figure 1. The extant murre, Uria, and the extant penguin, Aptenodytes to scale.

Figure 3. The extant murre, Uria, and the extant penguin, Aptenodytes to scale.

The LRT
(subset Fig. 1) nests penguins and murres with kingfishers (volant diving birds, Fig. 4) and the giant stork-like kingfisher, Jabiru, (which, of course, does not dive). These are close to loons + grebes (poorly flying diving birds) and terns (oceanic soaring diving birds, Fig. 5).

Figure 1. Megaceryle, the belted kingfisher may be a neotonous jabiru (genus: Jabiru).

Figure 4. Megaceryle, the belted kingfisher may be a neotonous jabiru (genus: Jabiru).

With Neornithes originating in the Early Cretaceous,
evolution had plenty of time to create penguins throughout the Cretaceous. But we don’t find their fossils then. Did Neornithes remain in small, out of the way enclaves, barely evolving, waiting, like mammals, to emerge after the Cretaceous?

Figure 3. Skeleton of Thalasseus, the crested tern.

Figure 5. Skeleton of Thalasseus, the crested tern. Scale bar = 10 cm.

Or did neornithine birds evolve throughout the Cretaceous
in areas that don’t often preserve fossils? Good question. 

Here’s a video worth seeing on Kingfishers.
Think of them as pre-penguins.

References
Slack KE. et al. 2006. Early Penguin Fossils, plus Mitochondrial Genomes, Calibrate Avian Evolution. Molecular Biology and Evolution, 23(6): 1144-1155.

online here.

http://www.otago.ac.nz/geology/research/paleontology/waimanu.html

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