Navigation Links
China fossil shows bird, crocodile family trees split earlier than thought
Date:5/18/2011

A fossil unearthed in China in the 1970s of a creature that died about 247 million years ago, originally thought to be a distant relative of both birds and crocodiles, turns out to have come from the crocodile family tree after it had already split from the bird family tree, according to research led by a University of Washington paleontologist.

The only known specimen of Xilousuchus sapingensis has been reexamined and is now classified as an archosaur. Archosaurs, characterized by skulls with long, narrow snouts and teeth set in sockets, include dinosaurs as well as crocodiles and birds.

The new examination dates the X. sapingensis specimen to the early Triassic period, 247 million to 252 million years ago, said Sterling Nesbitt, a UW postdoctoral researcher in biology. That means the creature lived just a short geological time after the largest mass extinction in Earth's history, 252 million years ago at the end of the Permian period, when as much as 95 percent of marine life and 70 percent of land creatures perished. The evidence, he said, places X. sapingensis on the crocodile side of the archosaur family tree.

"We're marching closer and closer to the Permian-Triassic boundary with the origin of archosaurs," Nesbitt said. "And today the archosaurs are still the dominant land vertebrate, when you look at the diversity of birds."

The work could sharpen debate among paleontologists about whether archosaurs existed before the Permian period and survived the extinction event, or if only archosaur precursors were on the scene before the end of the Permian.

"Archosaurs might have survived the extinction or they might have been a product of the recovery from the extinction," Nesbitt said.

The research is published May 17 online in Earth and Environmental Science Transactions of the Royal Society of Edinburgh, a journal of Cambridge University in the United Kingdom.

Co-authors are Jun Liu of the American Museum of Natural History in New York and Chun Li of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China. Nesbitt did most of his work on the project while a postdoctoral researcher at the University of Texas at Austin.

The X. sapingensis specimen a skull and 10 vertebrae was found in the Heshanggou Formation in northern China, an area with deposits that date from the early and mid-Triassic period, from 252 million to 230 million years ago, and further back, before the mass extinction.

The fossil was originally classified as an archosauriform, a "cousin" of archosaurs, rather than a true archosaur, but that was before the discovery of more complete early archosaur specimens from other parts of the Triassic period. The researchers examined bones from the specimen in detail, comparing them to those from the closest relatives of archosaurs, and discovered that X. sapingensis differed from virtually every archosauriform.

Among their findings was that bones at the tip of the jaw that bear the teeth likely were not downturned as much as originally thought when the specimen was first described in the 1980s. They also found that neural spines of the neck formed the forward part of a sail similar to that found on another ancient archosaur called Arizonasaurus, a very close relative of Xilousuchus found in Arizona.

The family trees of birds and crocodiles meet somewhere in the early Triassic and archosauriforms are the closest cousin to those archosaurs, Nesbitt said. But the new research places X. sapingensis firmly within the archosaur family tree, providing evidence that the early members of the crocodile and bird family trees evolved earlier than previously thought.

"This animal is closer to a crocodile, but it's not a crocodile. If you saw it today you wouldn't think it was a crocodile, especially not with a sail on its back," he said.


'/>"/>

Contact: Vince Stricherz
vinces@uw.edu
206-543-2580
University of Washington
Source:Eurekalert  

Related biology news :

1. Reforesting rural lands in China pays big dividends, Stanford researchers say
2. Rices origins point to China, genome researchers conclude
3. Solar greenhouses: Chinas winning solution to global energy crisis
4. Research literature from China listed in Medline
5. EARTH: Trade imbalance, America exports emissions to China
6. China PharmaHub Signs Distribution Agreement with Integrated Biometrics
7. Study examines risk of heterosexual HIV transmission in China
8. Virginia Techs Mueller receives friendship award from China
9. University of Utah microbubbles clean dirty soil in China
10. Measurements of CO2 and CO in Chinas air indicate sharply improved combustion efficiency
11. Chinas environmental challenges have global implications
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
China fossil shows bird, crocodile family trees split earlier than thought
(Date:3/9/2017)... Australia , March 9, 2017 4Dx ... prestigious World Lung Imaging Workshop at the University of ... was invited to deliver the latest data to world ... recognised event brings together leaders at the forefront of ... in lung imaging. "The quality of ...
(Date:3/6/2017)... 2017 Mintigo , the leader ... Predictive Sales Coach TM , its new artificial ... into Salesforce. This unique AI application will allow ... with deep knowledge of their customers and prospects ... Predictive Sales Coach extends Mintigo,s existing customer success ...
(Date:3/2/2017)... March 2, 2017 Australian stem cell and ... CYP), has signed an agreement with the Monash Lung ... Biomedicine Discovery Institute and Department of Pharmacology at Monash ... further preclinical study to support the use of Cymerus™ ... Asthma is a chronic, long term ...
Breaking Biology News(10 mins):
(Date:3/24/2017)... March 24, 2017 Agenus Inc. (NASDAQ: AGEN), ... antibodies and cancer vaccines, today announced participation at the ...  Annual William Blair and Maidstone Life Sciences conference "Cancer ... in New York, NY . Agenus ... 29 at 9:40 am: Robert B. Stein , ...
(Date:3/23/2017)... Research and Markets has announced the ... to their offering. ... The Global Market for Bioproducts Should Reach ... a CAGR of 8.9%, This research report ... seven major product segments: bio-derived chemicals, biofuels, pharmaceuticals (biodrugs and ...
(Date:3/23/2017)... Colo. , March 23, 2017  GlobeImmune, Inc. ... agreement for the sale of 12,835,490 shares of its ... NantWorks  ecosystem of companies. In connection with the sale of ... $100,000 in cash and issue to GlobeImmune 200,000 shares, ... stock. "We are pleased to enter ...
(Date:3/23/2017)... March 23, 2017 Kineta, Inc., a ... novel therapies in immuno-oncology, today announced the discovery ... molecule compounds that activate interferon response factor 3 ... demonstrate immune-mediated tumor regression in a murine colon ... who demonstrated complete tumor regression to initial drug ...
Breaking Biology Technology: