The evolutionary history of penguins is an issue that still intrigues researchers. Do they descend from flying birds or their ancestors were already non-flying birds? Why would they lose their ability to roam the skies? These questions are not easy to answer, but some hypotheses try to explain the mystery of their existence.
Genetic analyses indicate that members of the Spheniscidae family, the present penguins, evolved from non-flying birds whose ancestors were very different from what we could imagine. Their basal ancestor, the first to separate from other groups of birds, lived 71-68 million years ago, although this period can extend to 40-100 million years.
Some scientists believe that the earliest ancestors may have been flying birds that lived 60-65 million years ago during the Cretaceous Period. Because of their resemblance to cormorants, razorbills, puffins and other members of the Alcidae family, some scientists believe they are related to them, but the relationship is not very close; they are cases of convergent evolution, in which groups of species evolve independently but in a similar way.
In general, three groups of birds share many similarities with the modern penguins, suggesting that these groups could have some ancestor in common. These groups are:
A) Petrels and Albatrosses.
B) Loons.
C) Frigatebirds.
Podiceps and little grebes are also closely related to them.
A 2014 study entitled “Genomes of Two Antarctic Penguins,” reveals a vision of their evolutionary history and the molecular changes related to the Antarctic environment (Wang, Jung; Zhang, Guojie, David M. Lambert and others). It suggests penguins are brothers of the birds of the order Procellariiformes, which includes albatrosses, petrels, and storm petrels. In this sense, penguins and Procellariiformes are genetically close.
It is believed that the penguins are derived from a type of bird that is able to fly.
Somehow, the first ancestors of penguins are related to flying birds, but the truth is that modern penguins did evolve from non-flying birds; That’s the difference. Some believe that the “basal Penguin” lived somewhere in what was Gondwana, a large mass of land that was in the process of fragmentation and which would later become Australia, New Zealand, Antarctica and parts of South America.
It would be easy to think that the evolution of penguins took place in Antarctica, but this does not seem to be the case. From the fossils found, it is more likely that the first true penguins developed on the east coast of the South Island of New Zealand, in an area called Waipara. They conclude this because the oldest fossil fragments have been found precisely in New Zealand.
There is evidence that there lived the oldest penguin known, about 60-62 million years ago, which is named Waimanu manneringi. It was not much like the modern penguins, but it had lost already the ability to fly and had short wings that worked well for diving. Possibly, it was the size of a yellow-eyed penguin (Megadyptes antipodes).
But why did the ancestors stop flying and evolved into penguins? There are several hypotheses; The most accepted is that such ancestors increasingly adapted to the marine environment, where they found a large amount of food. Over the years, their swimming and diving necessities brought them structural changes, since they were no longer needed to fly for food; their wings were shortened and became flap-shaped, and its feather coat became dense.
Modern Penguins.
About 55 million years ago, penguins were already completely adapted to the life in water, in a warmer environment than today. After the disappearance of the dinosaurs, many marine reptiles also became extinct but penguins diversified, or in other words, slowly developed new species that occupied the ecological niches of some extinct animals. The evolution of modern penguins took place over the course of approximately 3 million years.
One of the descendants of the basal Penguin, named by scientists as “Penguin One,” is the ancestor of all penguins that now exist in the world, and it lived some 34.2-47.6 million years ago. Later, about 40 million years ago, a penguin appeared that has been classified in the genus Aptenodytes and named Penguin A, and that gave rise to the biggest species: the emperor penguin and the king penguin. It is important to know that this penguin was only one of the members of the genus since there were other species of the same that did not evolve successfully in the same way.
Later, Penguin B emerged, a member of the genus Pygoscelis and “father” of the present gentoo penguins, Adélie penguins, and chinstrap penguins. Penguin C gave birth to the Galápagos, Humboldt, Magellanic and African penguins, and one more ancestor is considered the father of the remaining species, including crested penguins. About 40-25 million years ago, penguins were already hot-blooded predators of fish, squid, and krill.
The number of species was formerly much greater than is now, as several became extinct over time because they did not adapt to new environmental conditions, competition with cetaceans for food or other reasons. The Miocene species were gigantic; For example, Anthropornis nordenskjoldi could have reached a height up to 1.7-1.8 meters, more or less the stature of some people! However, at that time this species began to decrease and finally got extinct, at the same time that whales and seals began to proliferate on Earth.
Sources:
https://en.wikipedia.org/wiki/Penguin#Evolution
https://www.theguardian.com/science/2014/aug/04/giant-penguin-fossil-antarctica
http://news.nationalgeographic.com/news/2006/04/0411_060411_penguins_2.html
http://news.nationalgeographic.com/news/2013/13/131320-penguin-evolution-science-flight-diving-swimming-wings/
BioExpedition Publishing © 2017.
