Jurassic saw fastest mammal evolution

Date:: July 16, 2015
Source:: University of Oxford
Summary:: Mammals were evolving up to 10 times faster in the middle of the Jurassic than they were at the end of the period, coinciding with an explosion of new adaptations, new research shows.

Research led by Oxford University scientists shows that mammals were evolving up to ten times faster in the middle of the Jurassic than they were at the end of the period. An illustration showing docodonts, now extinct mammals that saw an explosion of skeletal and dental changes (including the special molar teeth that give them their name), in the Middle Jurassic.

Credit: April Neander

Mammals were evolving up to ten times faster in the middle of the Jurassic than they were at the end of the period, coinciding with an explosion of new adaptations, new research shows.

Early mammals lived alongside the dinosaurs during the Mesozoic era (252-66 million years ago). They were once thought to be exclusively small nocturnal insect-eaters, but fossil discoveries of the past decade -- particularly from China and South America -- have shown that they developed diverse adaptations for feeding and locomotion, including gliding, digging, and swimming.

To find out when and how rapidly these new body shapes emerged a team led by Oxford University researchers did the first large-scale analysis of skeletal and dental changes in Mesozoic mammals. By calculating evolutionary rates across the entire Mesozoic, they show that mammals underwent a rapid 'burst' of evolutionary change that reached its peak around the middle of the Jurassic (200-145 million years ago).

The team comprised researchers from Oxford University in the UK and Macquarie University in Australia. A report of the research is published in Current Biology.

'What our study suggests is that mammal 'experimentation' with different body-plans and tooth types peaked in the mid-Jurassic,' said Dr Roger Close of Oxford University's Department of Earth Sciences, lead author of the report. 'This period of radical change produced characteristic body shapes that remained recognisable for tens of millions of years.'

The team recorded the number of significant changes to body plans or teeth that occurred in mammal lineages every million years. During the mid-Jurassic the frequency of such changes increased to up to 8 changes per million years per lineage, almost ten times that seen at the end of the period. This is exemplified by therian mammals, the lineage leading to placental mammals and marsupials, which were evolving 13 times faster than average in the mid-Jurassic, but which had slowed to a rate much lower than average by the later Jurassic. This 'slow-down' occurred despite the increase in the number of mammal species seen in this later period.

'We don't know what instigated this evolutionary burst. It could be due to environmental change, or perhaps mammals had acquired a 'critical mass' of 'key innovations' -- such as live birth, hot bloodedness, and fur -- that enabled them to thrive in different habitats and diversify ecologically,' said Dr Close. 'Once high ecological diversity had evolved, the pace of innovation slowed.'

Multituberculates, for instance, saw radical changes to their skeletons and teeth during the mid-Jurassic. However, by the end of the period they had evolved their rodent-like body shape and distinctive teeth, a form that, despite diversifying into hundreds of different species, they would generally retain until they went extinct around 130 million years later.

'This is characteristic of other 'adaptive radiation' events of this kind, such as the famous 'Cambrian explosion',' said Dr Close. 'In the Jurassic we see a profusion of weird and wonderful bodies suddenly appear and these are then 'winnowed down' so that only the most successful survive. What we may have identified in this study is mammals' own 'Cambrian explosion' moment, when evolutionary experimentation ran wild and the future shape of mammals was up for grabs.'

Story Source:

The above post is reprinted from materials provided by University of Oxford. Note: Materials may be edited for content and length.

Journal Reference:

Roger A. Close, Matt Friedman, Graeme T. Lloyd, Roger B.j. Benson. Evidence for a Mid-Jurassic Adaptive Radiation in Mammals. Current Biology, 2015 DOI: 10.1016/j.cub.2015.06.047

University of Oxford. "Jurassic saw fastest mammal evolution." ScienceDaily. ScienceDaily, 16 July 2015. <www.sciencedaily.com/releases/2015/07/150716123846.htm>.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Feathered cousin of famous movie star dino unearthed in China

Date:: July 16, 2015
Source:: University of Edinburgh
Summary:: A newly identified species of feathered dinosaur is the largest ever discovered to have a well-preserved set of bird-like wings, research suggests. Palaeontologists working in China unearthed the fossil remains of the winged dinosaur -- a close cousin of Velociraptor, which was made famous by the Jurassic Park films.

This is an artist's impression of Zhenyuanlong suni.

Credit: Chuang Zhao

A newly identified species of feathered dinosaur is the largest ever discovered to have a well-preserved set of bird-like wings, research suggests.

Palaeontologists working in China unearthed the fossil remains of the winged dinosaur -- a close cousin of Velociraptor, which was made famous by the Jurassic Park films.

Researchers say its wings -- which are very short compared with other dinosaurs in the same family -- consisted of multiple layers of large feathers. They found that the species' feathers were complex structures made up of fine branches stemming from a central shaft.

Although larger feathered dinosaurs have been identified before, none have possessed such complex wings made up of quill pen-like feathers, the team says. Scientists have known for some time that many species of dinosaur had feathers, but most of these were covered with simple filaments that looked more like hair than modern bird feathers.

This latest discovery suggests that winged dinosaurs with larger and more complex feathers were more diverse than previously thought.

The species belonged to a family of feathered carnivores that was widespread during the Cretaceous Period, and lived around 125 million years ago, the team says.

The near-complete skeleton of the animal -- which is remarkably well preserved -- was studied by scientists from the University of Edinburgh and the Chinese Academy of Geological Sciences. The fossil reveals dense feathers covered the dinosaur's wings and tail.

The newly discovered species -- named Zhenyuanlong suni -- grew to more than five feet in length. Despite having bird-like wings, it probably could not fly, at least not using the same type of powerful muscle-driven flight as modern birds, researchers say.

It is unclear what function the short wings served. The species may have evolved from ancestors that could fly and used its wings solely for display purposes, in a similar way to how peacocks use their colourful tails, researchers say.

The study is published in the journal Scientific Reports. The research was supported by Natural Science Foundation of China, the European Commission, and the US National Science Foundation.

Dr Steve Brusatte, of the University of Edinburgh's School of GeoSciences, who co-authored the study, said: "This new dinosaur is one of the closest cousins of Velociraptor, but it looks just like a bird. It's a dinosaur with huge wings made up of quill pen feathers, just like an eagle or a vulture. The movies have it wrong -- this is what Velociraptor would have looked like too."

Professor Junchang Lü, of the Institute of Geology, Chinese Academy of Geological Sciences, who led the study, said: "The western part of Liaoning Province in China is one of the most famous places in the world for finding dinosaurs. The first feathered dinosaurs were found here and now our discovery of Zhenyuanlong indicates that there is an even higher diversity of feathered dinosaurs than we thought. It's amazing that new feathered dinosaurs are still being found."

Story Source:

The above post is reprinted from materials provided by University of Edinburgh. Note: Materials may be edited for content and length.

Journal Reference:

Junchang Lü, Stephen L. Brusatte. A large, short-armed, winged dromaeosaurid (Dinosauria: Theropoda) from the Early Cretaceous of China and its implications for feather evolution. Scientific Reports, 2015; 5: 11775 DOI: 10.1038/srep11775

University of Edinburgh. "Feathered cousin of famous movie star dino unearthed in China." ScienceDaily. ScienceDaily, 16 July 2015. <www.sciencedaily.com/releases/2015/07/150716101509.htm>.