Kumimanu wasn’t simply exceptionally huge; it additionally ranks among the many oldest penguin fossils but discovered. Each its age and its dimension make Kumimanu vital to understanding the astonishing transformation that turned a lineage of flying birds into flightless swimmers.
The 18 trendy species of penguin, starting from the coast of Antarctica to the Galápagos Islands on the Equator, are impressively tailored to aquatic life. Inflexible, blade-shaped wings allow them to shoot by means of the water at as much as 22 miles an hour. File-setting human swimmers don’t even attain six m.p.h.
However their diversifications to water have additionally left them unable to fly. When penguins haul out to relaxation or rear their younger, they will solely waddle about on stumpy legs. “They’re so unbirdlike that many individuals wouldn’t know they’re birds,” Dr. Mayr mentioned.
Whereas penguins might look profoundly totally different from different birds, their DNA factors to an in depth kinship to such species as albatrosses and petrels. These birds all fly over water to hunt for prey, hinting that the ancestors of penguins might have, too.
Auks, which may dive over 100 ft underwater, could also be a residing mannequin of the primary penguins.
Birds accumulate mutations of their DNA at a roughly clocklike charge, permitting scientists to estimate when their lineages branched aside. Research counsel that penguins diverged across the time of the mass extinction that struck the planet about 66 million years in the past.
A mixture of large volcanic eruptions and an asteroid impression are believed to have been accountable for the worldwide disaster. Among the many victims had been large marine reptiles and dinosaurs (except for birds, that are feathered dinosaurs). The mass extinctions marked the tip of the Mesozoic Period and the start of the Cenozoic, which continues in the present day.
The primary penguin fossils had been uncovered in 1859, and since then greater than 50 species have been recognized. The oldest of those, present in New Zealand, date again about 60 million years. Often called Waimanu, the oldest recognized penguins lived just some million years after the mass extinctions.
The brand new fossil penguin, Kumimanu, was found from bones packed in a rock on a New Zealand seashore. Realizing that it was nearly as outdated as Waimanu, Dr. Mayr and his colleagues eagerly studied Kumimanu for a greater image of early penguin evolution.
To see the way it was associated to different species, the scientists drew an evolutionary tree and located that Kumimanu and Waimanu belonged to its farthest branches. Their lineages have been extinct for tens of thousands and thousands of years.
Against this, all residing penguins belong to a younger department of the tree. They share a standard ancestor that lived solely about 15 million years in the past.
Kumimanu and Waimanu had been already flightless, however they nonetheless held onto some primitive traits not present in residing penguins.
“Their beak seemed way more like a stork’s,” Dr. Mayr mentioned. “Most likely they speared their prey.”
The early penguin wing was not but the quick, stiff blade discovered on residing penguins. “They had been in all probability in a position to bend it a bit of farther than penguins can in the present day,” Dr. Mayr mentioned. “There was extra risk for flexing.”
The place Waimanu and Kumimanu differ from one another is of their peak. Waimanu stood simply two and a half ft excessive. Kumimanu was greater than twice as tall.
“We already knew penguins had been round, and flightless, just some million years after the extinction,” mentioned Daniel T. Ksepka, a paleontologist on the Bruce Museum in Greenwich, Conn., who was not concerned within the new research. “The brand new fossil reveals they achieved immense sizes very quickly as properly, which is cool.”
Dr. Mayr speculates that the dramatic origin of penguins was sparked by the mass extinctions that marked the daybreak of the Cenozoic. Abruptly the oceans had been emptied of lots of their largest predators. Penguins may adapt to catching prey underwater with out a lot competitors, or worry.
“It’s an informed guess that is sensible, however there’s no rock-solid proof,” mentioned Dr. Mayr.
One technique to check that speculation can be to uncover earlier fossils. “What can be cool can be to have a flying ancestor of penguins,” Dr. Mayr mentioned.
The early Cenozoic oceans didn’t simply open up the way in which for the evolution of flightless aquatic birds, Dr. Mayr speculated. It might have additionally fostered the evolution to huge sizes.
Pure choice favors light-weight flying birds as a result of they need to work so arduous to remain aloft. Penguins don’t pay that price. Getting larger may need introduced benefits, as properly. A big physique makes prey tougher to kill.
The tree drawn by Dr. Mayr and his colleagues additionally reveals that penguins grew to become giants many occasions over. Whereas Kumimanu belonged to an early lineage of huge penguins, different lineages produced their very own giants as not too long ago as 27 million years in the past.
The rise of marine mammals might have doomed large penguins. As mammals moved into the oceans and advanced into whales and seals, they might have outcompeted the birds.
Each seals and penguins want to search out protected seashores the place they will mate and lift their younger, for instance. It’s doable that the seals pushed the large penguins out, whereas smaller penguins survived.
“The massive query for me will not be why there have been so many penguins within the early Cenozoic, however why there are not any large penguins in the present day?” Dr. Mayr mentioned.
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