麻豆淫院

It鈥檚 official: There really was a giant, flightless bird with a head the size of a horse鈥檚 wandering about in the winter twilight of the high Arctic some 53 million years ago.

The confirmation comes from a new study by researchers from the Chinese Academy of Sciences in Beijing and the University of Colorado Boulder that describes the first and only fossil evidence from the Arctic of a massive bird known as听Gastornis. The evidence is a single fossil toe bone of the 6-foot tall, several-hundred-pound bird from Ellesmere Island above the Arctic Circle. The bone is nearly a dead ringer to fossil toe bones from the huge bird discovered in Wyoming and which date to roughly the same time.

罢丑别听Gastornis听(蹿辞谤尘别谤濒测听Diatryma) fossil from Ellesmere Island has been discussed by paleontologists since it was collected in the 1970s and appears on a few lists of the prehistoric fauna there, said Professor Thomas Stidham of the Chinese Academy of Sciences in Beijing. But this is the first time the bone has been closely examined and described, he said.听Gastornis听fossils also have been found in Europe and Asia.

鈥淲e knew there were a few bird fossils from up there, but we also knew they were extremely rare,鈥� said Eberle, an associate professor in geological sciences who conducts research on fossil mammals, reptiles and fishes. In addition to the听骋补蝉迟辞谤苍颈蝉听bone from Ellesmere, another scientist reported seeing a fossil footprint there, probably from a large flightless bird, although its specific location remains unknown, Eberle said.

A paper by Stidham and Eberle appears in the most recent issue of听Scientific Reports,听an open access, weekly journal from the publishers of听Nature.

About 53 three million years ago during the early Eocene Epoch, the environment of Ellesmere Island was probably similar to cypress swamps in the southeast U.S. today, Eberle said. Fossil evidence indicates the island, which is adjacent to Greenland, hosted turtles, alligators, primates, tapirs and even large hippo-like and rhino-like mammals.

Today Ellesmere Island is one of the coldest, driest environments on Earth, where temperatures can drop to minus 40 degrees Fahrenheit in winter, said Eberle, also the curator of paleontology at the University of Colorado Museum of Natural History.

Originally thought to be a fearsome carnivore, recent research indicates听骋补蝉迟辞谤苍颈蝉听probably was a vegan, using its huge beak to tear at foliage, nuts, seeds and hard fruit.

A second Ellesmere Island bird from the early Eocene also is described by Stidham and Eberle in the new paper. Named听Presbyornis, it was similar to birds in today鈥檚 duck, goose and swan family but with long, flamingo-like legs. The evidence was a single humerus, or upper wing bone, collected by the same paleontology team that found the听Gastornis听产辞苍别.

尝颈办别听Gastornis,听笔谤别蝉产测辞谤苍颈蝉听was mentioned in several lists of Ellesmere Island fauna over the years but the bone had never been described, said Stidham.

Stidham compared casts of听Presbyornis听bones excavated in ancient Wyoming to the single bone from Ellesmere Island, including all of the marks for muscle attachments. 鈥淚 couldn鈥檛 tell the Wyoming specimens from the Ellesmere specimen, even though it was found roughly 4,000 kilometers (2,500 miles) to the north,鈥� he said.

While the diversity of plants and animals on Ellesmere was surprisingly high in the early Eocene, one of the biggest challenges to life on the island may have been the Arctic winters, said Eberle. 鈥淪ince Ellesmere Island is high above the Arctic Circle, the lights still went out there for several months of the year, just as they do today.鈥�

It is not known whether听Presbyornis听migrated north to Ellesmere Island every year or lived there year-round, said Stidham. 鈥淕iven the fossils we have, both hypotheses are possible,鈥� he said. 鈥淭here are some sea ducks today that spend the winter in the cold, freezing Arctic, and we see many more species of waterfowl that are only in the Arctic during the relatively warmer spring and summer months.鈥�

The paleontology team working on Ellesmere Island in the 1970s and who found the听Gastornis听补苍诲听Presbyornis听bones in the 1970s included Mary Dawson, Robert 鈥淢ac鈥� West, Howard Hutchinson and Malcolm McKenna.

The new study has implications for the rapidly warming Arctic climate, primarily a result of greenhouse gases being pumped into Earth鈥檚 atmosphere by humans.

鈥淧ermanent Arctic ice, which has been around for millennia, is on track to disappear,鈥� Eberle said. 鈥淚鈥檓 not suggesting there will be a return of alligators and giant tortoises to Ellesmere Island any time soon. But what we know about past warm intervals in the Arctic can give us a much better idea about what to expect in terms of changing plant and animal populations there in the future.鈥�

The study was funded in part by the U.S. National Science Foundation, the Chinese Academy of Sciences and the Chinese Natural Science Foundation.

Jim Scott is senior science editor for the听.