Friday, January 29, 2010

Dinosaur Avian Ancestor

Experts unveil dino, oldest known ancestor of birds

By Tan Ee Lyn

HONG KONG (Reuters) - China has unearthed the fossil of a two-legged carnivorous dinosaur that lived 160 million years ago and which researchers have identified as the earliest known member of a long lineage that includes birds.

The "Haplocheirus sollers" had a long, narrow skull, many small teeth and powerful biceps and forelimbs, which enabled it to hunt primitive lizards, small mammals and reptiles.

The individual, believed to be a young adult when it died, had a long tail and a total body length of between 190 and 230 cm. (6 feet 2 inches to 7 feet 6 inches), the researchers wrote in a paper published in the journal Science.

It was found in orange mudstone beds in the Junggar Basin in China's far western Xinjiang region.

"It has unique features but it shares some features with birds. It moves its hands sideways, like how birds can fold their wings. Its head, vertebral column, hind limbs, hands are all bird like," said Professor Xu Xing at the Chinese Academy of Sciences' Institute of Vertebrate Paleontology & Paleonanthropology.

"Their legs have four digits like modern birds, with three digits pointing forwards. The first digit, unlike in birds which point backwards, this one points sideways," he said.

Xu, a member on a research team led by Jonah Choiniere at the George Washington University in Washington, said that while this species shared some features with birds, it was more like a "typical carnivorous dinosaur."

"The most salient feature of this group is their forelimbs, they are predators. They have three claws on their hands, used to catch other animals. They have very bizarre forelimbs, they are very short but very stout and very strong," said Xu.

"Primitive lizards, small mammals, mammal-like reptiles were all possible food items," he told Reuters by telephone.

"They represent the earlier stage in the evolution of birds, but they are not birds. You can say they are early ancestors of birds ... and very slowly, it (the lineage) turned into birds."

This species belongs to the family of Alvarezsauridae -- a bizarre group of bird-like dinosaurs -- and its discovery pushes the fossil record of this family back by 60 million years into the Late Jurassic period (145 million to 161 million years ago).

The Haplocheirus is about 60 million years older than the next oldest known Alvarezsauroid, which was discovered in Argentina in 1991 and lived 95 million years ago during the Cretaceous period (65 million to 145 million years ago).

"We know birds are derived from dinosaurs. But most of our original fossils are from the Cretaceous period. Now we hope to find more Jurassic fossils. This way we can find more direct evidence to prove that birds evolved from dinosaurs," said Xu.

(Reporting by Tan Ee Lyn; Editing by Ron Popeski)

More Teeth Than T.rex

New Tyrannosaur Had More Teeth Than T. Rex

The newly found toothy tyrannosaur featured a hole in its skull and was recovered from New Mexico.

By Jennifer Viegas Thu Jan 28, 2010 07:00 PM ET
Discovery News

A newly found 29-foot-long tyrannosaur flashed more teeth than the well-known Tyrannosaurus rex, with which it shared a common ancestor, according to a paper in the latest Journal of Vertebrate Paleontology.

Remains of the badlands dinosaur, Bistahieversor sealeyi, were collected in the first paleontological excavation from a federal wilderness area, the Bisti/De-na-zin Wilderness of New Mexico. The dino's remains were removed VIP-style, airlifted by a helicopter operated by the Air Wing of the New Mexico Army National Guard.

"Bistahieversor sealeyi is the first valid new genus and species of tyrannosaur to be named from western North America in over 30 years," said co-author Thomas Williamson, curator of paleontology at the New Mexico Museum of Natural History.

It lived 74-75 million years ago, close to 10 million years before T. rex emerged. The earliest known tyrannosaurs date to about 167 million years ago and came from the American West, according to Carr. It is now therefore believed that the rough and tumble Tyrannosauridae family was born in the U.S.A.

Several features distinguish the new dinosaur, according to Williamson's partner on the project, Thomas Carr, who is director of the Carthage Institute of Paleontology and an assistant professor of biology at Carthage College.

It had around 64 teeth, while adult T. rex, had just 54.

However, Carr added, "The teeth of B. sealeyi were smaller and narrower than those of T. rex, which had the largest teeth among the tyrannosauroids."

The new dinosaur also had an unusual hole in its head, just above the eyes. The hole has not been seen on any other tyrannosaur, and might have helped to lighten the load of its head.

"The opening above the eye was produced by an air sac within the skull that removed bone where it was not needed," said Carr. "The opening would not have been visible when the animal was alive (because) it would have been covered by skin."

The dinosaur also had a "complex joint at its forehead." Carr explained that usually these animals show three prongs of the snout extending into the forehead, but the New Mexico beast had seven.

This complex joint might have functioned to stabilize and prevent motion at the joint," he said.

B. sealeyi additionally possessed a keel, or prominent ridge, that extended from the bottom edge of its lower jaw. The scientists aren't sure of the ridge's purpose, but it is another unique feature.

The researchers now think the deep snout characteristic of many tyrannosaurs evolved in the common ancestor of these animals, which lived west of the Western Interior Seaway, a shallow sea that split North America into two subcontinents during the Late Cretaceous.

Tyrannosaurs to the west of the sea continued to evolve this striking head feature, according to Carr, while those to the east retained the more primitive shallow snout. He believes that "selective pressures necessary for producing a deep snout were simply not in action" on the eastern side of the sea.

The badlands dinosaur along with other fossils collected from the Bisti site and from the lands of the Navajo Nation are currently on display at the New Mexico Museum of Natural History.

Wednesday, January 27, 2010

Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds

Fucheng Zhang(1), Stuart L. Kearns(2), Patrick J. Orr(3), Michael J. Benton(2), Zhonghe Zhou(1), Diane Johnson(4), Xing Xu(1) & Xiaolin Wang(1)

1. Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China
2. Department of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK
3. UCD School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland
4. Planetary and Space Sciences Research Institute, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK

Correspondence to: Michael J. Benton(2) Zhonghe Zhou(1) Correspondence and requests for materials should be addressed to M.J.B. (Email: mike.benton@bristol.ac.uk) and Z.Z. (Email: zhonghe@yeah.net).

Spectacular fossils from the Early Cretaceous Jehol Group of northeastern China have greatly expanded our knowledge of the diversity and palaeobiology of dinosaurs and early birds, and contributed to our understanding of the origin of birds, of flight, and of feathers. Pennaceous (vaned) feathers and integumentary filaments are preserved in birds and non-avian theropod dinosaurs, but little is known of their microstructure. Here we report that melanosomes (colour-bearing organelles) are not only preserved in the pennaceous feathers of early birds, but also in an identical manner in integumentary filaments of non-avian dinosaurs, thus refuting recent claims that the filaments are partially decayed dermal collagen fibres. Examples of both eumelanosomes and phaeomelanosomes have been identified, and they are often preserved in life position within the structure of partially degraded feathers and filaments. Furthermore, the data here provide empirical evidence for reconstructing the colours and colour patterning of these extinct birds and theropod dinosaurs: for example, the dark-coloured stripes on the tail of the theropod dinosaur Sinosauropteryx can reasonably be inferred to have exhibited chestnut to reddish-brown tones.

Nature advance online publication 27 January 2010 doi:10.1038/nature08740; Received 21 September 2009; Accepted 10 December 2009; Published online 27 January 2010

Monday, January 25, 2010

Model may shed light on Dinosaur Flight

Birdlike Dinosaur Was Adept Glider

By Dennis Normile--ScienceNOW Daily News 25 January 2010

How did birds learn to fly? The first flight tests of a foam model of a four-winged, feathered dinosaur suggest that early birds may have started their aviation careers by gliding down from trees.

The fight over bird flight evolution is one of the longest-running and most heated debates in paleontology. Were the first flyers arboreal creatures that initially glided from tree tops to the ground? Or were they bipedal ground runners whose evolving wings allowed them to take progressively longer jumps? There is still no complete consensus.

In recent years, researchers have tried to determine the flight capabilities of early birds with mathematical analyses and computer simulations. And at least one group has built a physical model based on fossils and put it in a wind tunnel. Taking a different tack, biomechanics specialist David Alexander of the University of Kansas, Lawrence, along with colleagues there and at Northeastern University in Shenyang, China, reconstructed a specimen of Microraptor, a dinosaur notable for having four wings. Microraptor is a type of dromeosaur, a genus of birdlike dinosaurs.

The team made a skeleton, covered the "bones" with a clay "body," and added plumage made from modern pheasant feathers trimmed to match impressions preserved in fossils. The researchers used this feathered reconstruction to make urethane foam models that they launched from various heights, recording the distance, velocity, and angle of each glide. "Microraptor was an adept glider and would have had little difficulty gliding from tree trunk to tree trunk," the authors report today online in the Proceedings of the National Academy of Sciences.

Alexander, who says he was added to the team of paleontologists because of his knowledge of flying airplane models, says he doesn't know of any other groups that have tried to fly models of dinosaurs. This new approach is "probably one of the most effective" ways of determining the flight capabilities of extinct animals, says Zhonghe Zhou, a paleontologist at the Chinese Academy of Sciences' Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. He expects similar experiments based on fossils of other animals could help clarify how avian flight originated.

Julia Clarke, a paleontologist at the University of Texas, Austin, agrees that models could be useful, but they have to be constrained by an understanding of anatomy. In the case of Microraptor, "I'm not convinced that in life the animal could have gotten into some of the postures that they are exploring," she says. She also thinks the community has moved beyond the dichotomy of trees-down or ground-up hypotheses, focusing on a more nuanced set of questions such as what anatomical evolutions enabled powered flight.

Sunday, January 17, 2010

Alligators breath like birds; implications for dinosaur respiration

15 January 2010 by Shanta Barley --New Scientist

Birds, crocodiles and dinosaurs have much in common – including, it turns out, their breath. The hyper-efficient breathing system of birds is shared with alligators, and probably evolved in archosaurs, the common ancestor of crocodilians, birds and dinosaurs.

The researchers who have discovered the system in alligators believe it may have given dinosaurs the competitive edge over the ancestors of mammals following the mass extinction at the end of the Permian period, 250 million years ago.


Thanks to one-way airflow, birds are far more efficient breathers than mammals. When they breathe in, air does not go directly into the lungs. Instead, it enters the air sacs, where it is stored briefly before passing into the lungs at the next inhalation. In this way, air enters and exits a bird's lungs at different points – in via the air sacs, out via the windpipe – allowing them to maintain near-constant, one-way airflow through their lungs and extract up to two-and-a-half times as much oxygen per breath as a mammal.

Previous research has suggested that one-way air flow is unique to birds and evolved specifically to allow them to make oxygen-demanding flights. It was also thought that the bellows-like air sacs were critical for pumping air one way.

Those conclusions have been toppled by the new study, in which devices to measure airflow were surgically implanted into the lungs of live alligators.


Gators flayed

Colleen Farmer of the University of Utah in Salt Lake City also placed the flow meters into the dissected lungs of four dead alligators, which the team then filled with air using a giant syringe. What they found was that alligator lungs function very much like birds'.


Alligators don't have air sacs like birds, but the researchers think an unusual airway that sits on either side of the alligator trachea may do the same job.

Per Ahlberg of Uppsala University in Sweden agrees that the efficient breathing system probably evolved in a common archosaur ancestor of crocodilians, birds and dinosaurs. "Swift, long-legged animals that might have relied on the rich oxygen supply provided by a one-way airflow were abundant in the early lineages of these groups," he says.

Farmer goes one step further and argues that the system would have allowed archosaurs to outcompete synapsids – the ancestors of mammals – following the end-Permian mass extinction.

"Oxygen levels were really low during the early Triassic [after the Permian], so the evolution of unidirectional airflow, which boosts oxygen delivery to muscles, may have made archosaurs more capable of vigorous exercise than synapsids," she says


Journal reference: Science, DOI: 10.1126/science.1180219

Wednesday, January 6, 2010

Proceratosaurus was Ancestor to Tyrannosaurs

ScienceDaily (Jan. 6, 2010) — Tyrannosaurus rex and related large carnivorous dinosaurs together form the family Tyrannosauridae. A long forgotten fossil skull in the collections of the Natural History Museum in London has now provided crucial clues to the early stages of the lengthy evolutionary history of these fearsome predators. Almost a century after its discovery, the specimen, named Proceratosaurus, has now been recognized as the oldest known relative of the Tyrannosauridae.


With the help of an ultramodern imaging technique, a team of researchers led by Dr. Oliver Rauhut from LMU Munich and Dr. Angela Milner from the Natural History Museum London, have been able to show that Proceratosaurus resembled its approximately 100-million-years younger descendant T. rex in a number of ways. The teeth, the jaws, and the structure of the cranial cavity of the two species have many features in common. Proceratosaurus weighed only about 40 kg, says Rauhut. Nevertheless, like the later tyrannosauroids, the animal obviously depended on its powerful biting apparatus. Later modifications of the jaw muscles and the overall structure of the cranium then gave rise to the perfect hunting weapon wielded by T. rex.

Among the dinosaur specimens housed in the collections of the Natural History Museum in London is an almost complete skull that was found in the West of England about 100 years ago. The fossil was initially misclassified, but was later recognized as representing an otherwise unknown genus, which was named Proceratosaurus. The skull has only recently been subject to detailed study by a team led by the palaeontologist Dr. Oliver Rauhut, who holds dual appointments in the Department of Geological and Environmental Sciences at Ludwig-Maximilians-Universit├Ąt (LMU) in Munich and the Bavarian State Collection for Paleontology and Geology, and Dr Angela Milner, Associate Keeper of Palaeontology at the Natural History Museum in London.



This skull, which had been overlooked for so long, turns out to be a spectacular find. Proceratosaurus is the earliest known ancestor of the family Tyrannosauridae (named after its most famous representative Tyrannosaurus rex). Proceratosaurus and T. rex were both bipedal carnivores and each had a massive body, short and stubby forelimbs, a powerful tail, and sharp teeth set in a bulky skull. The best known members of the family, T. rex, lived during the late cretaceous period, although smaller species are known from the earlier Jurassic era.



Little is known about the origins and later evolution of this important group of dinosaurs. Proceratosaurus could now cast much needed light on the process. "It is quite astonishing that this fossil has received so little attention, since it is one of the best preserved dinosaur skulls in Europe," reports Rauhut. Parts of the skull that were still embedded in the rock matrix and these had to be exposed carefully by preparator Scott Moore-Fay at the Natural Histsory Museum in London; the team also used an advanced imaging technique to probe the detailed structure of the fossil.


"Computerized tomography is a wonderful method, because it offers us a non-destructive means of visualizing the internal structures of fossils," says Angela Milner, the researcher responsible for the specimen at the Natural History Museum, who personally took the fossil to Texas, where the tomographic scan was performed. Detailed studies of the resulting images and of the skull itself were subsequently carried out back in London.



The investigations uncovered a wide range of features in the cranial cavity, teeth and jaws that Proceratosaurus shares with the huge T. rex, despite the fact that the Proceratosaurus skull is about 100 million years older and much smaller. The Proceratosaurus cranium was about five times less massive than that of its mighty relative, and the intact animal appears to have weighed only about 40 kg. Mature specimens of Tyrannosaurus, in contrast, weighed in at up to eight tons.



Because the Proceratosaurus skull already displays characteristics that are typical of its later descendants, the powerful jaw with its slicing teeth was probably the animal's most important weapon. "It is likely that this hunting strategy developed first," says Rauhut. The basic tool kit was perfected in later tyrannosaurids: The skull became more robust and the jaw muscles larger and, overall, the body increased enormously in size. Proceratosaurus also confirms that the tyrannosauridae developed over a very long stretch of time, and gave rise to a great diversity of forms. Further members of the family surely await discovery."



The study was financially supported by the SYNTHESIS program of the European Union.