Wednesday, April 11, 2012

Paleobirding:What Birds Looked Like 125 Million Years Ago

Looking at ancient bird fossils is an opportunity to see what birding might have been like millions of years ago. Back then, many birds had enormous teeth, long snouts and long, bony tails.

"The birds that lived during the age of the dinosaurs were very different from the birds that live today," said Los Angeles County Natural History Museum curator and dino-bird expert Luis Chiappe. "And it would have been a completely different experience to go out birding in the Mesozoic Era."

During the Mesozoic, from 250 to 65 million years ago, the planet also looked and felt very different. Earth was much warmer, and the ice caps didn't exist. The continents were only beginning to split into their modern configurations. Sea levels were higher, and large dinosaurs ruled the land. Primitive birds emerged at this time and became prey for non-avian dinosaurs, which were usually much bigger.

We've compiled a quick guide to birding in China's primitive forest-filled aviary, which thrived about 125 to 120 million years ago. We've tried to give a sense of how big these ancient birds were by comparing them to modern birds. The comparisons are based on the size of the femur, or thigh muscle.


Jeholornis is the most primitive bird in this guide. It had very tiny teeth, short clawed wings and a very long, bony tail. "In that sense, it still retains the long, bony tails of the dinosaurs," Chiappe said.

It had feet capable of clasping branches, which suggests it might have lived or have spent a good amount of time perching in trees, Chiappe says.  It didn't have a hard, ossified breast bone, which suggests it probably wasn't very good at flying. "They could have fluttered from one tree to another," Chiappe said. But these turkey-vulture-sized birds probably weren't long-range flyers.


Sapeornis was a rather large bird, probably around the size of a turkey vulture. It had very long, broad wings and spade-shaped teeth on its upper jaw only, Chiappe says. Some scientists think Sapeornis was probably a seed-and-grain feeder because it had stomach stones, structures that help digest these foods. Like Jeholornis, it had a very powerful grasping foot, so it may have lived in trees.


Confuciusornis were a diverse group of beaked birds with very long wings and very long feathers. Some had two ornamental feathers that could be as long as the animal's body (as pictured above).

These crow-sized ancient birds also had very powerful claws. Some researchers think they could have used them to climb trees, but Chiappe isn't convinced. "It's hard to imagine they had independent mobility," he said. "You can't really be grasping something when your hands are filled with long, stiff feathers. They're just not going to move in the same way."

Researchers have found hundreds of well-preserved Confuciusornis fossils in what might have been ancient lakes. But there's no evidence, like webbed feet for example, that these animals could swim, Chiappe says.

"These were flyers," he said. They had very large breast bones, indicating they probably had very large breasts and flight muscles. They also had well-developed upper limbs, which good modern flyers have.

Many Confuciusornis specimens, like the ones above, contain multiple birds, suggesting they probably died in some catastrophic event, like a volcanic eruption, Chiappe says. For this reason, Confuciusornis fossils are very abundant. "That's why we're able to do studies with samples comparable in size to what modern ornithologists would use for their own studies," he said.


Changchengornis had a short, hooked beak, a forked tail, elaborate plumage and four claws on its feet. It didn't have a strong perching foot. The kestrel-sized creature was smaller than its close relative, Confuciusornis. It didn't have any teeth, and it probably ate insects rather than hard seeds that required cracking, Chiappe says.


The starling-sized Longipteryx had long wings, large powerful claws,  and a long snout. "But it didn't have a beak because it had big teeth!" Chiappe said. These animals probably ate fish. Their massive teeth, which were restricted to the tip of the snout, may have helped them capture slippery prey, he says. Longipteryx didn't have a keeled breast bone, like many good flyers do. But because it was small and had long wings, it was probably a decent enough flyer, he says.


"Rapaxavis was a very little guy," Chiappe said. "It was very lightly built, and it had a long, slender snout with tiny little teeth." Unlike some of its contemporaries, it didn't have any claws on its "hands," but it did have four on its feet, which it used to perch. The sandpiper-sized creature probably used its long, thin snout to forage for crustaceans, maggots and larvae. Yum.


Pengornis was around the size of a pigeon and had massive, dull teeth that "looked like onions or the domes of a Russian church," Chiappe said. These teeth would not have been good for puncturing, but would have been great for cracking the shells of seeds, snails or crabs.


Hongshanornis was a tiny bird with long legs and long toes. Like Rapaxavis, it was about as big as a sandpiper. "It was a wader," Chiappe said. It probably lived close to water and ate invertebrates that lived on the lakeshore.  It had a strong beak with teeth so tiny some scientists argue it was probably toothless. If it did have teeth, they were probably not very good ones, Chiappe says. These birds also had long wings and a very long-feathered tail.


Eoenantiornis was probably a perching bird. It had a rounded tail, a short snout and very sharp teeth that were probably good for chomping on bugs. It was about the size of an oriole.


Longirostravis was a very slender, delicate bird, like Rapaxavis, Chiappe says. It had tiny peg-like teeth at the end of its snout. And like Rapaxavis, it may have also poked through mud to find food.


"Zhongornis was a very interesting little guy," Chiappe said. "It's the intermediate between long-tailed and short-tailed birds." The sparrow-size Zhongornis had fairly long "fingers" with claws, a short snout, a short tail and it may have been toothless, he says.


Yanornis was one of the most anatomically modern paleo-birds, Chiappe says. The pigeon-size bird had teeth, a long snout, a fanned tail, long wings, and a keeled breastbone that supported strong flight muscles.

Fossils of this ancient bird typically have stomach stones, which help animals to digest plants, leaves, grains or seeds. Many modern herbivores have them, so it's likely Yanornis fed on grains, Chiappe says. Paleontologists have also found specimens with fish remains in their gut, suggesting "they ate fish," he said. "I would imagine they probably lived close to the lakeshore."

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