Were dinosaurs doing well or doomed to extinction?

Today, the press are widely reporting on a paper about the extinction of the dinosaurs. Except, the vast majority are not reporting on the paper. They’re reporting on the speculation of the lead author. The BBC, The Guardian, The Daily Mail, etc are all reporting his version, which, to my understanding, does not actually follow the conclusions of the paper.

I’m going to stick my neck out and say they’re wrong.

The paper uses the most recent dinosaur fossil discoveries and new analytical techniques to examine in closer detail than ever before the last few million years of the dinosaurs. There were other environmental pressures during this time; intense volcanism, temperature shifts, and sea-level swings. This has led to the suggestion that dinosaurs were already stressed out by the meteorite strike, and it was simply the final straw.

The press release, prepared by the lead author’s institution, the University of Edinburgh, goes full in for this view. Under the headline ‘Dinosaurs fell victim to perfect storm of events, study shows‘,  the opening line of the release is: ‘Dinosaurs might have survived the asteroid strike that wiped them out if it had taken place slightly earlier or later in history, scientists say.’

Cool, I thought, fascinating new development. But then I read the paper. It does not say this. In fact, it pretty much says the opposite.

Styracosaurus
Some large herbivores, like this styracosaurus, may have been declining.
Credit: LadyofHats via Wikimedia Creative Commons.

In areas of North America, there is some evidence that the large herbivore groups of the hadrosaurs and ceratopsians (think parasaurolophus and triceratops) were declining in species diversity. This may have left the communities reliant on them more vulnerable to cascading extinctions under external pressure such as the asteroid impact. But, everywhere else the fossil record is good enough to examine, the evidence says overall dinosaur species diversity was not declining.

The Natural History Museum’s dinosaur expert is also an author on the paper. Through our press office he released a statement. It mentioned nothing about the supposed ‘perfect storm of events’, instead saying: ‘Although some types of dinosaurs were already declining in numbers before the famous asteroid impact, in most cases this impact is the smoking gun for the cause of the extinction.’ In other words, the asteroid was it for most groups.

Confused, I called him. He seemed to be as baffled as me. In the end, he concluded that the lead author from Edinburgh was likely just taking the case of the herbivore decline to hyperbole for the sake of a more exciting news story (it’s based on his own research), and that I should probably ‘quietly ignore it’.

*

This story raises a couple of interesting points. Doubtless, the versions of the story that suggest dinosaurs might have survived if the asteroid had hit at a different time will be read more and shared more. It is a more exciting story. But it’s not really what the study showed.

Sure, the paper’s point is also that there are few areas in the world with complete enough fossil records, and even where there are we can’t yet tease apart the effects of the asteroid and the last pulse of volcanism, which occurred at nearly the same time. This means the story could, and likely will, change again with more research, as most science does.

But for the lead author to put so much weight behind a singular case in the paper for the sake of a story is bizarre (not least because usually, when talking to the press, scientists rather emphasize the caveats and inconclusiveness of their results). I’m frankly surprised so many science correspondents went for it too. He must be quite the compelling character.

But for myself, even though I admit my story for the Museum will probably be read less (it’s hard to make ‘Yeah, it was the asteroid’ that compelling), I wanted to stick to the overall message of the study, quoted from the paper here:

Our current knowledge of the dinosaur fossil record provides no indication of obvious long-term declines in global biodiversity over the final 15 Myr of the Cretaceous (although some North American herbivores did diminish in diversity), no major dinosaur groups went extinct during this time, and a diverse assemblage of abundant dinosaur species persisted until the very end of the Cretaceous in local faunas in North America and Europe. Whatever killed the dinosaurs seems to have been focused at the very end of the Maastrichtian, within a few hundred thousand years of the K–Pg boundary [end of the Cretaceous period].

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