The oldest penguin fossils yet found suggest that at least some ancestors of modern birds survived the mass extinction that killed off the dinosaurs.
The 58- to 62-million-year-old bones unearthed in New Zealand belong to four specimens from a previously unknown genus of ancient penguin called Waimanu.
Ewan Fordyce, a paleontologist at the University of Otago in Dunedin, helped analyze the fossils.
He says the seabirds' age, combined with DNA sleuthing by colleagues, make a "strong case" that modern birds appeared well before dinosaurs died out some 65 million years ago.
"When [we] saw that penguin lineages were established by 60 or 62 million years ago, it became clear that other bird lineages, which were more remote from penguins, must have had earlier origins," he said.
The study describing the ancient penguins and the associated theory of a dino-era origin for modern birds appeared in last month's online issue of the journal Molecular Biology and Evolution.
Dino-Era Waterbirds
The name Waimanu comes from the Maori words wai (water) and manu (bird).
Similar in size to present-day yellow-eyed or king penguins, Waimanu penguins stood about 26 to 30 inches (65 to 76 centimeters) tall.
(See related photos of New Zealand's modern native birds.)
The ancient birds could flex their wings slightly at the elbow and, like their modern counterparts, used their wings as hydrofoils to "fly" underwater.
A government geologist found the first Waimanu penguin specimen in the mid-1980s on a rock outcrop in the Waipara region, today a wine-growing area near Christchurch on New Zealand's South Island.
"It turned out to be … a sort of missing-link penguin," Fordyce, the Otago paleontologist, said.
Fordyce is a past recipient of research grants from the National Geographic Society Committee for Research and Exploration.
An amateur fossil-hunter found three more closely related specimens in the 1990s. The additional bones, composing nearly a full skeleton, gave Fordyce and his colleagues a more complete picture of the birds.
But only in more recent years did the researchers realize that they were looking at a significant new group of ancient penguin.
Microfossil dating techniques firmly place the seabirds in the age range of 58 million to 62 million years old, Fordyce says, making them the world's oldest known penguins.
"We are absolutely sure that they come from early Paleocene time, the time that immediately followed the extinction of dinosaurs," which occurred about 65 million years ago, Fordyce said.
Prior to the discovery, the oldest previously described penguin was a fragmentary specimen from Antarctica estimated to be some 55 million years old.
Waimanu pushes the age of early penguins back by millions of years, Fordyce says.
This fact, plus the knowledge that the penguins were highly specialized, suggests the birds descended from other, still-modern species that lived many millions of years further back in time.
"We can use that quite ancient penguin to argue [that] all the other modern [bird] groups—many of the other modern groups at least—[arose] back in Cretaceous times contemporaneous with the dinosaurs," Fordyce said.
Feathered Family Tree
Lacking a clear fossil record, scientists have debated precisely when modern birds first took flight. Some experts believe the group first diversified during the reign of dinosaurs.
Others argue that modern birds appeared only after dinosaurs died out in what proponents of the theory call a "Big Bang" of rapid bird evolution.
While the penguin study may not definitively settle the flap, it does highlight the growing use of genetic detective work by researchers attempting to pinpoint the evolutionary origins of man and beast. (See the Genographic Project.)
Study co-author David Penny, a geneticist with the Allan Wilson Centre for Molecular Ecology and Evolution at Massey University in Palmerston North, analyzed avian DNA sequences to construct a family tree of bird evolution.
Penny and colleagues identified genetic differences between living bird species and the rate at which those DNA changes, or gene mutations, likely occurred over time.
That information enabled his team to use the newly found penguin fossils and a recently described duck relative from the Cretaceous period (145.5 to 65.5 million years ago) found in Antarctica as reference points to establish a time frame for bird evolution.
"From the [DNA] sequences we can build [an evolutionary] tree fairly easily …" Penny said. "But that doesn't tell you anything about the times [certain species appeared] until you can get these calibration points from the fossils."
Based his team's work, Penny estimates that modern birds first appeared around 90 million years ago.