Birds of the family Plotopteridae, who lived in the late Eocene and early Miocene, the Japanese Islands and the Pacific coast of North America was similar to the penguins not only a lifestyle, but a structure of bones, reported in the Journal of Zoological Systematics and Evolutionary Research. The authors suggest that the relatives of plotopterids and penguins are independently from each other developed the ability to dive on the basis of short shallow dives that birds have started swooping into the water.
Plotopteridae — extinct family of flightless seabirds. Its representatives in the late Eocene and early Miocene (35-17 million years ago) lived in the Northern part of the Pacific Ocean. For the first time, their remains found on the coast of California in 1969. The majority of the discovered bones belong to the skeleton of the limbs, although there are fragments of the skull. When their structure is compared with the structure of the skeleton of the ancient giant penguins (e.g. Anthropornis nordenskjoeldi), it was found that they are very close. Most likely, plotopteridae, and penguins in the water worked in the first place wings, not feet. However, the skulls of birds of these two groups in detail before did not compare.
Moreover, it was not clear to what extent the relationship of these organisms. The family Plotopteridae traditionally belong to the order researsh (Suliformes), but whom have the penguins (family Spheniscidae), were unclear. In 2005, the two families proposed to be attributed to one group Suloidea with maesaceae (Anhingidae) and baklanove (Phalacrocoracidae). Ten years later, the same authors re-analyzed the structure of the skeletons of these birds and molecular data and has presented another option: the penguins still outside Suloidea.
Now Gerald Mayr (Mayr Gerald) from the Research Institute and natural history Museum name of Senckenberg, the chief author of all these works, and his colleagues from New Zealand and the United States compared coracoid (the so-called crows ‘ bones; the birds their structure largely determines the nature of the movements of the forelimbs), the left branch of the lower jaw, and shoulder, elbow and some other limb bones of the ancient giant penguins (Waimanu manneringi and others), plotopterids and modern smieszek, cormorants and other researsh.
The analysis confirmed that bone adaptation to swimming penguins and plotopterids very similar. This also applies to the structure of the limbs, and the structure of the jaws. Most likely, their ancestors had first dived into the water from the air and dived shallowly, and then increasingly used the wings to paddle. However, two groups of birds have adapted to moving in the water, apparently independently. So plotopteridae and the penguins — an example of convergent evolution.