In a study published in the journal Biology Letters, a team of international scientists has charted the largest dinosaur tree to date, and in so doing, has indicated that the massive lizards may have evolved 20 million years sooner than most in the paleontology field have been saying.
In the study, the team described how they produced the new tree using probabilistic techniques and why the new conclusions show that the dinosaurs might have survived a prior mass extinction.
By looking at dinosaur bones, researchers have been capable of figuring out reasonable estimates for the time period that dinosaurs lived. However, these kinds of estimates always have some margin for error.
Creating Dinosaur Family Trees
In this most recent effort, the scientists used two probabilistic techniques to produce an immense tree representing nearly 1,000 species and calculated the date of first appearance of what we now call dinosaurs. The outcomes from the previous research studies matched the new study’s calculations, giving support to its conclusions.
The new tree revealed that dinosaurs first appeared about 250 million years ago. Moreover, the tree reveals what are thought to have been the first birds stretching off the tree around 160 to 180 million years ago. It also indicates the group that includes all known birds emerged around 60 to 110 million years ago– during the Late Cretaceous, which, strangely enough, was before the mass extinction that killed off all the dinosaurs.
The tree also revealed dinosaurs emerged before the oldest known dinosaur fossil, from a Nyasasaurus, dated to just 240 million years ago. To put it another way, scientists will have to count on math and scientific principle if they are to acknowledge the new tree; at least until an older fossil is discovered.
The report also said there is some evidence that suggests the timeline might be pushed back another 10 million years or so.
If the new timeline is correct, would mean the animals that became dinosaurs somehow were able to survive the Permo-Triassic extinction, thought to be the biggest mass extinction that ever took place.
Image credit: James St. John/Flickr
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