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Fw: Oldest Dinosaur Fossil



Palaeontologists have found what is likely to be the oldest known 

dinosaur, filling in a yawning evolutionary gap.

A study in Biology Letters describes Nyasasaurus parringtoni, a new 
species from 10-15 million years before the previous earliest dinosaur 
specimens.

It walked on two legs, measured 2-3m in length with a large tail and 
weighed between 20 and 60kg.

The find suggests that many millions of years passed between dinosaurs' 
first members and their dominance on land.

"It fills a gap between what we previously knew to be the oldest dinosaurs 
and their other closest relatives," report co-author Paul Barrett, of the 
Natural History Museum in London, told BBC News.

"There was this big gap in the fossil record where dinosaurs should've 
been present and this fossil neatly fills that gap."

However, the team behind the work has stopped short of definitively 
calling N parringtoni the earliest dinosaur, because the fossil skeletons 
used to define it were incomplete: one upper arm bone and six vertebrae.

The early evolution of dinosaurs is difficult to unpick, as a rich variety 
of reptiles were proliferating at the time - and some may even have 
independently evolved characteristics that are associated with dinosaurs.

The researchers, from the University of Washington and University of 
California Berkeley in the US and the Natural History Museum, re-examined 
a number of bones that were first collected from what is now Lake Malawi 
in southern Africa.

They saw a few features that are unambiguously those of dinosaurs - 
notably what is called an "elongated deltopectoral crest" that served as 
an anchor for strong pectoral muscles.

Lead author of the research Sterling Nesbitt, of the University of 
Washington Seattle, led a team that in 2010 reported the finding of 
dinosaurs' oldest relative, a member of a group called the silesaurs.

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It now appears that those creatures shared the southern part of the 
supercontinent Pangaea - now South America, Africa, Antarctica and 
Australia - with N parringtoni.

"Those animals were the earliest of this group that led up toward 
dinosaurs," explained Dr Barrett. "Now this takes dinosaurs back to the 
right kind of time when those two groups would have split apart from each 
other."

As it closes that evolutionary gap, it shows that dinosaurs did not start 
out as dominant as they later became.

"We push the origin of dinosaurs further back in time to a time when lots 
of reptile groups are evolving," Dr Barrett said.

"Dinosaurs start out as a very insignificant group of reptiles - all 
relatively small animals, relatively rare in comparison with other reptile 
groups - and it's only a bit later in their history that they suddenly 
explode and take over as the dominant forms of life for nearly 100 million 
years."

http://www.bbc.co.uk/news/science-environment-20594147

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