These hips did lie…

Every now and again, scientists make mistakes. Some of these are, as Bob Ross would call them, happy little mistakes, that end up being incredible scientific leaps (think Penicillin). In other cases, they’re less positive, but can still provide cautionary tales for future work. Today, I want to talk about one of the latter cases. This story starts with my discovery of a very delicate bone from the Dinosaur Park Formation in 2015. The bone, shown below, would perplex me for another two years, because it is very unusual and difficult to identify.

GFF_2252
UALVP 56200, the mystery bone in question.

There were some things that we could know about the mystery identity of the bone right off the bat. First, the bone has hollow spaces inside of it, which would have been filled with air or fat while the animal was alive. Very few animals have these spaces, and most notable among these are theropod dinosaurs (and their bird descendants), and pterosaurs, the ancient flying reptiles.

At first, we thought that the specimen must have been part of a theropod, because pterosaurs are very, very rare in Dinosaur Park. So, we compared it to almost every theropod bone we could think of. One clue that seemed to help us out is a very deep depression in the bone, that was clearly a socket for another bone. If we think about our own bodies, there aren’t many places where there are such ball-and-socket joints: the shoulders, the hips, and potentially the jaw joint. However, it just didn’t fit with any of these bones in a theropod dinosaur.

GFF_0269
The hips of a theropod dinosaur Nemegtomaia, showing that nothing really looks quite like UALVP 56200

So, we compared it to the other option: pterosaurs. At this point, I asked for the expertise of Liz Martin-Silverstone (read her blog here), a previous University of Alberta grad, who is an expert on pterosaurs. As soon as we started comparing the bone to the hips of pterosaurs, it started to make a lot of sense. It looked just like a pterosaur hip bone, but it was huge! This makes sense, when we consider what kind of pterosaurs are known from the Dinosaur Park Formation: large, semi-terrestrial azhdarchids, some of which get as big as planes. This was great, because we don’t know of any hip bones of azhdarchids, and the strong musculature and robust construction of this specimen supported previous hypotheses of terrestriality in azhdarchids.

Pelvic Illustration
Our interpretation of the bone as a pterosaur pelvis, showing the insertions of different muscles associated with walking. © Funston et al. 2017

A couple months later, we had the paper written and submitted. During the peer-review process, the reviewers were positive and agreed with our interpretation of the specimen. After making some changes they suggested, the paper was published and open to the world!

This is where things took a turn. A couple weeks after the paper came out, I got an email from the editor of the paper, saying that another scientist tweeted that our specimen was actually a tyrannosaur skull bone called a squamosal. I immediately had a sinking feeling in my stomach. With all the difficulty in identifying the specimen, is it possible that we missed something? In short, yes. After looking at some tyrannosaur squamosals in our collections, it became clear that what we had was actually a broken piece of a squamosal. We hadn’t considered the option because when a tyrannosaur skull is all in one piece, you can’t see the part of the bone we have–its covered by other bones. But, the other scientist was right, and we were wrong.

Correction Fig 2
Reinterpretation of the specimen (pictured at left) as a tyrannosaur squamosal (pictured at right) in top view (A,B) and side view (C,D). © Funston et al. 2018

This realization made me seriously doubt myself and whether I was qualified to be working on specimens like this. Luckily, I am surrounded by an extremely supportive group of peers and mentors, and they reassured us that mistakes happen and they in no way reflect our ability to be scientists. There was only one way to proceed, as hard as it may have been: we had to issue a correction to our error. We reinterpreted the specimen as a tyrannosaur squamosal, and talked about some of the features it showed that hadn’t been noted before.

This was a hard lesson to learn, but I’m glad that I learned it early in my career. It’s important to swallow your pride and admit your mistakes, especially in a constantly changing discipline like science. Science moves forward by proving our past theories wrong. Although it would have been nice for this hypothesis to stand more than two weeks, a good scientist accepts new evidence and lets go of previous ideas. The most important thing is that I learn from this, and learn to live with my mistakes–maybe with a little fun.

Sensu
A tyrannosaur, sensu (in the sense of) Funston et al. 2017

2 Replies to “These hips did lie…”

  1. I know you know this Greg as we’ve exchanged e-mails about it, but I’m happy to add publicly that I was one of the referees on this paper. I’ve worked on tyrannosaurs and pterosuars (as I know had the other ref) and I was quite happy with the interpretation too. We all make mistakes and unusual and broken bones are the easiest to get wrong. There should be no shame attached to making an error on this one.

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