we’re going to take a heretical look at the origin of penguins, those short-legged, super-insulated, flightless, fish- & squid-eaters. Some can dive for 22 minutes down to 550 meters.
According to Wikipedia
the relationships of the penguin subfamilies (order: Sphenisciformes) and the placement of penguins among the birds “is not resolved.” By contrast, in the LRT the relationship of penguins among birds is completely resolved.
like Waimanu, are known from Antarctica and New Zealand from the early Paleocene. Waimanu was flightless and likely swam with both its short wings and paddling feet. This derived bird at the K-T boundary points to a much earlier radiation of more primitive, crane-like extant birds, apparently starting just before Yanornis in the Early Cretaceous.
Figure 1. Subset of the LRT focusing on extant birds, especially penguins.
In the large reptile tree
(LRT, 1089 taxa) penguin ancestors going back to Devonian fish are recovered. However, presently and provisionally two taxa are proximal penguin sisters in the LRT and these are derived from even more basal and high-energy terns, swifts and kingfishers.
Figure 1. Cinclus, the dipper is basal to penguins.
Dippers like Cinclus (Fig. 2) traditional nest with Passer, the seed-eating sparrow. Not here (Fig. 1). Cinclus flies, walks and dips into fast moving freshwater streams to walk underwater. It flies underwater on short wings and it likes cold waters. Nasal flaps prevent water from entering the nostrils. The bones are solid to decrease buoyancy and the feathers are waterproof. The eyes can focus underwater.
Dippers can remain underwater for up to 30 seconds. They have a slower metabolism, despite their active lifestyle. Dippers do not live in colonies and they are smaller than their phylogenetic predecessors.
(the Lilliput effect) as we have seen with reptiles, mammals, pterosaurs, snakes, bats, dinosaurs, turtles, etc., leads to key internal structural changes. In the case of Cinclus, these apparently involve those initial adaptations to cold and water. And with these traits in its toolbox, the descendants of Cinclus were free to grow larger, get fatter, loser their ability to fly, gain the ability to handle deeper water and withstand colder nesting grounds away from predators.
FIgure 2. Cinclus, Uria and Aptenodytes, three taxa in the origin of penguins. Despite their apparent differences, the LRT nests these three taxa together in a single clade.
Representing another transitional phase
Murres like Uria (Fig. 2; 45cm), traditional nest with snipes, plovers, terns, stilts, gulls puffins and auks (= Charadriiformes),. That’s a pretty diverse clade. Some of these also appear in the penguin clade of the LRT. Many workers consider murres to be unrelated to penguins, despite appearances. Murres are all north of the equator, while penguins stay south. Uria has pelican-like plumage (black and white) and is better adapted to swimming underwater (up to 4 minutes) with a longer torso and longer sternum. Digit 1 becomes a vestige and the rib cage extends nearly to the ankle. Murres live in colonies near sea waters.
Penguins like Aptenodytes (Fig. 3) traditionally nest with loons, like Gavia. Here (Fig. 1) they don’t. Penguins are flightless, trend toward larger, can swim better and seek larger prey. Finger 1 disappears. The pygostyle straightens out. The scapula grows larger. The metatarsus becomes shorter than the pedal digits. Again, these are all minor and gradual accumulations of traits.
Cinclus cinclus (Linneaus 1758 (Sturnus cinclus); Borkhausen 1797; 18 cm long) is the extant white-throated dipper. Its short wings whirr swiftly and without pauses or glides. From a perch it will walk into the water and deliberately submerg. It ‘flies’ underwater. Prey includes aquatic invertebrates. This is one of the most basal taxa among neognath birds. This clade developed a very deep sternum.
Uria lomvia (Linneaus 1758; 45cm tall) is the extant thick-billed murre. It is a strong flyer, both in the air and underwater. Basal to penguins, and derived from Cinclus, Uria also has an elongate sternum, two more dorsal vertebrae + ribs, and short wings.
Here is a unique video of YouTube. of a beluga whale toying with a tiny dipper… or is it the other way around. Enjoy! Nullius in verba
Figure YouTube: Click to see the entire charming video of a beluga whale making friends with a tiny dipper.
Deguine, J-C 1974. Emperor Penguin: Bird of the Antarctic. The Stephen Greene Press, Vermont.
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.