Dinosaurs May Have Evolved Up To 20 Million Years Earlier Than Thought

[edd]

Dinosaurs ruled the earth for at least 165 million years. During this period they evolved into a whole menagerie of wonderful and fantastical forms, and are survived today by the birds that flit from branch to branch in your garden. But when they first emerged from the evolutionary tree is a murkier story. It now seems that they may have evolved up to 20 million years earlier than thought.

The results come from a study published in Biology Letters, in which researchers from the Natural History Museum, London, have created the most detailed dinosaur tree ever formed. Using two separate methods, they created a massive phylogenetic tree that includes close to 1,000 different species of dinosaurs, enabling them to trace the animals right back to their roots.

Both methods came up with strikingly similar results, indicating the validity of the outcome. They both showed that while the oldest dinosaur fossil to have ever been dated, known as Nyasasaurus, is thought to be 240 million years old, the data from the trees suggest that dinosaurs may have evolved at least 10 million years earlier, and potentially up to 20 million years earlier.

This is possibly not too surprising. The dating of such ancient fossils comes with some leeway, as well as considering just how patchy the fossil record from this long ago for dinosaurs is. For example, while Nyasasurus is the best contender for the oldest dinosaur discovered so far, there is a full 12-million-year gap before the next one pops up. What is interesting, however, is how researchers are able to use phylogenetics to help fill in these blanks, and predict where there are fossils to be found that could potentially predate the known one.

It also means that if the dates are to be believed, the direct early ancestors to dinosaurs may already have been around before the dramatic Permian extinction event that occurred 252 million years ago, and so were one of the few lineages that managed to survive. Also known as the Great Dying, it is thought that up to a staggering 95 percent of all species alive at the time bit the dust, in what was the largest mass extinction event that has ever occurred.

Not only that, but the data also shows that the branch that includes all known birds may have split off between 108 and 69 million years ago, meaning that they may have already been flying, or at the very least gliding, around before the asteroid that killed off all their other relatives hit.

 

http://www.iflscience.com/plants-and-animals/dinosaurs-may-have-evolved-up-to-20-million-years-earlier-than-thought/

[ashcraft]

On 11/11/2016 at 10:59 AM, edd said:

meaning that they may have already been flying, or at the very least gliding, around before the asteroid that killed off all their other relatives hit.

 

 

Sigh........now everything written becomes questionable

 

Brent Ashcraft

[Wrangellian]

The Wikipedia article for Nyasasaurus says it comes from the Anisian stage, while the date 240mya is currently within the overlying Ladinian. Meaning it must be 242+ (I guess that falls within the range of "about 240", but if all I had to go on was that date, 240my, then I would assume the oldest dino to be Ladinian. It would be nice if stages could be mentioned along with dates, but I know popular media wants to keep out the clutter for layman readers.

Anyway, looks like my timescale needs yet another edit!

 

[tmaier]

The paper is using two methods of extrapolation to arrive at this +20 million year divergence number. So, they take hard data and then use that to project backwards in time to guess when the actual event happened. It is an interesting paper, and the results seem pretty believable, but keep in mind that extrapolation is a gamble, and it might be grossly wrong.

For people unfamiliar with extrapolation, imagine I have data points that I measured A, B, C, D, E, and F. They are in chronological order, and they are "hard data", in that I know them to be true. Extrapolation is when I want to guess what is the data BEFORE A, or AFTER F. I'm going to guess outside of the hard data range. There are different methods for making this type of guess, and this paper used two methods, and found that they agreed pretty closely with each other.

Intrepolation is when you have that same sequence of hard data mentioned above, and you want to know what happened BETWEEN to data points, for example, what happened half way between D and E? That seems easy and safe to do, but it depends on the predictability of the system. A wildly undilating curve can have a lot happening inbetween D and E, and attempting to guess can lead to gross errors again.

Evolution is pretty lumpy and not easy to predict, so interpolation and extrapolation projections of evolution are going to be very "iffy".

Anyway, this paper is an example of the modern use of compuational biology, and this type of data analysis is becoming very popular.

[doushantuo]

the sister taxon to dinosauria?

 

nyasa20120949.full.pdf

one man's apomorphy is another man's plesiomorphy,to quote somebody.

Thank heavens the Triassic timescale is completely calibrated.

So what was the CI of those trees?