Archive for March, 2017

Buried Treasure – Dave Hone

I could hardly expect everyone else to write about their own papers without taking a turn myself at some point. In may case it’s a fairly recent paper that I’d like to cover, my paper in the Journal of Zoology on sorting out hypotheses for behaviour when dealing with fossil species. OK, so it’s only a few years old and things take time to accrue citations, but it does seem to have had very little impact given the raft of papers I have seen that (I think) would really benefit from taking a look at what I and my coauthor Chris Faulkes proposed.

Over the last few years I’ve become increasingly invested in looking at definitions and how they are used. When you are trying to look at multiple species and compare them, or get a sense of something of the state of play for an issue like the ratio of different life stages of animals, it’s enormously helpful if everyone is using the same definitions. Unfortunately the opposite is true, people use different words to mean broadly the same thing (without ever clarifying it), or the same word to mean very different things depending on context (again, without ever providing an explicit definition) and the whole situation becomes a bit of a mess. My paper on defining juveniles and adults for dinosaurs is a case in point and similarly, there’s lots of unhelpful use of the term ‘social’ with out reference to other works (especially on living taxa) as covered in my paper on Protoceratops and what it means to be ‘social’.

In short, we need to be careful about how things are defined because that’s important for making data comparable, but it’s also an issue for testing hypotheses. If it’s not clear what you mean by ‘juvenile’ then it’s very hard to say whether or not this is the correct assignment, or using it to assess a growth pattern etc. The other side of this, is whether or not a hypothesis is really credible in the first place. I think with palaeontology we are so used to dealing with incomplete specimens and limited data generally that hypotheses based on little evidence is the norm, but it does seem that when it comes to behaviour (and / or ecology) these can get erected based on almost nothing at all, and really only add to a long list of vague statements that don’t really add anything to our understanding of how animals lived. I won’t pick on any specific examples, but it’s not hard to find hypotheses like ‘this animal may have been a piscivore / scavenger / hunted in packs / migrated long distances’ and so on based on the flimsiest of lines of evidence. Statements about the sociality of whole clades of taxa based on a set of footprints of two individuals together is not something that should be taken seriously, but too often it’s not only published but then picked up and carried forwards.

So my paper on establishing hypotheses was designed to be something that could help provide guidance towards making hypotheses stronger. What lines of evidence would likely be useful to support a case, which would be weaker, how can that evidence be best integrated with available data or our understanding of the behaviour of living animals? Taken together, is an idea even supported by enough data to make it worth evoking as a formal hypothesis and if so, how can this best be formalised to the species or specimen in hand in a way that is supported by the evidence and is most amenable to further support or even formal testing later on?

I think this is really important. We as a field have become so much better at being rigorous when it comes to assessing ideas about descent, relationships, ages, functional morphology, evolutionary patterns and many more, but I do think that behaviour really lags here. Too many vague and unsupported hypotheses are not just in the literature, but are entering the literature and I do hope that the ideas in this paper will help slow up some of this and get people (authors, referees and editors) to take a more critical look at terms and how they are used, and in particular the support for hypotheses about behaviour.

Hone, D.W.E. & Faulkes, C.J. 2014. A proposed framework for establishing and evaluating hypotheses about the behaviour of extinct organism. Journal of Zoology.

Buried Treasure – Andy Farke

Sometimes, even research that gets a fair bit of press can get overlooked–particularly for little tidbits in the paper that might get obscured by the “big picture” stuff.

One of the coolest fossils I’ve ever worked on is a “baby” Parasaurolophus from southern Utah. The fossil–the smallest, youngest, and most complete of this kind of duck-billed dinosaur (hadrosaur) ever discovered–was found in 2009 by one of my high school students. The resulting 2013 paper received international press and has racked up a decent number of citations since. The fossil was even invited to travel to Japan as part of the 2016 Dinosaur Expo, where it was viewed by nearly a million people!

I am incredibly proud of the work, a collaborative effort with high school students, myself, and bone expert Sarah Werning, and consider it one of the best pieces of research I have ever published. Yet, there is one tiny angle that seems to get overlooked by a lot of people: the beak.

The skull on our baby Parasaurolophus is accompanied by an impression of the horny beak that lined the front bones of the upper jaw. Notably, it shows that the skull was not a terribly accurate representation of life appearance–the beak itself extended far beyond the bony anatomy.

Importantly, the baby Parasaurolophus was not the first hadrosaur to show this, either. Fossils of Edmontosaurus, reported as far back as the 1920s, revealed a similar structure, and strongly indicate that an elongated horny beak was pretty typical across “duck-bills”. In fact, they weren’t really duck-bills at all, but more like “shovel-beaks” (Brian Switek has a great post on this topic). The beak extension created a big scoop that was perfect for mowing off vegetation!

Long-beaked sauropod by Panzarin

Long-beaked hadrosaur by Lukas Panzarin

Despite a long history of knowledge about the beaks in these animals, very few artists include the structure in their reconstructions. I’m not sure why this is, but even very recent reconstructions by many talented artists simply follow the bony outline of the jaws. It is just a tiny blow to my ego that this tidbit from our Parasaurolophus paper (and work by others) gets overlooked!

Hadrosaurs looked quite a bit different than usually pictured. So, if you are an artist, or advising artists, give hadrosaur beaks an extra little bit of love!

Postscript

If I have to pick an underappreciated historical paper, I would say it has to be the classic monograph on the anatomy of Protoceratops by Barnum Brown and Eric Schlaikjer. It’s got a ton of careful anatomical description and some really brilliant thoughts on ontogeny (changes during growth). There is unfortunately a bit of a misconception arising that long-ago paleontologists didn’t think about ontogeny in any serious way–Brown and Schlaikjer show this isn’t true. Peter Dodson’s 1975 paper on ontogeny in hadrosaurs is another great one–he was one of the first people to show that what had been split into multiple species of duckbilled dinosaurs were in fact young and old individuals of a single species. This work by Brown, Schlaikjer, Dodson, and others paved the way for ongoing investigations of ontogeny today, many of which are using methods like histology to add another layer of data to the questions.

Citations

Brown, B., and E. M. Schlaikjer. 1940. The structure and relationships of Protoceratops. Annals of the New York Academy of Sciences 40:133–266.

Dodson, P. 1975. Taxonomic implications of relative growth in lambeosaurine hadrosaurs. Systematic Zoology 24:37–54.

Farke, A. A., D. J. Chok, A. Herrero, B. Scolieri, and S. Werning. 2013. Ontogeny in the tube-crested dinosaur Parasaurolophus (Hadrosauridae) and heterochrony in hadrosaurids. PeerJ 1:e182.

Morris, W. J. 1970. Hadrosaurian dinosaurs bills–morphology and function. Los Angeles County Museum Contributions in Science 193:1–14.

Versluys, J. 1923. Der Schädel des Skelettes von Trachodon annectens im Senckenberg-Museum. Abhandlungen Der Senckenbergischen Naturforschenden Gesellschaft 38:1–19.

A cornucopia of pterosaur papers

I’ve already covered here at some length my paper on the taxonomy of some of the Asian dsungaripterids as related to the rediscovery of some missing material of Noripterus. That paper is my entry to a volume that I have edited with Mark Witton and Dave Martill* and is the collected works that comes off the back of the 2015 Flugsaurier meeting in Portsmouth. This is being published by the Geological Society of London, an august institute to host this, and a nice hark back to the truly seminal 2003 volume they produced from the back of the Toulouse pterosaur meeting. It will be very hard to meet the standards of that collection (not least as it contained some absolutely fundamental papers on systematics and critical specimens) but I hope not to stand too much in that particular shadow.

Unlike many previous volumes this has the advantage of papers being published online as they come in and so we do not need to wait for the final paper to be sorted before the volume becomes available. That means that a number of papers are already available to read, even though not all of them are yet back from edits by authors and approval by the editorial team. We do hope to have the paper version out by the end of the year, but in the meantime there’s a pile of papers to enjoy.

There’s a diversity of subjects covered here with papers describing new specimens, revisions of existing taxa, new genera being named (or resurrected), a major new phylogenetic analysis, studies on muscles, jaws, and wings as well as various other bits and bobs. I won’t go through them one by one, you can see the list here (and it will continue to update as papers come in). The volume is, sadly, not OA but the production of PDFs means that authors have copies that can be readily disseminated so as with many papers, an e-mail should secure you a copy (and people like to know their work is being read). There should be something in here for everyone (provided of course you like pterosaurs) but here’s a select group of personal highlights so far (and some other important and interesting papers are coming).

First off would be Mark Witton’s excellent review of pterosaurs in food chains – both things they ate and that ate them. This deals exclusively with direct evidence of diet (stomach contents and the like) of which there is a fair bit, rather than so much work which is understandably often built on inferences about these relationships. It’s an excellent foundation for this area which is growing quite rapidly.

Next would be Chris Bennett’s paper with Paul Penkalski on a bizarre Pteranodon that has a striped skull. This isn’t (sadly) colour patterning or soft tissues but remarkably seems to be a pattern of the bone itself. It’s really quite strange and shows that even pterosaurs we know well can pop up with some big surprises.

Finally there’s Colin Palmer’s paper on the properties of pterosaur wing membranes. Although not the first to tackle this subject, since the last major review and set of hypotheses on their performance, we have learned a lot about the structure of the soft tissues, the layers that go into it, and the size and shape and extent of the main wing as well as the orientations in which it likely functions. That makes a synthesis like this very useful as both a review of where we are and what we might expect as well as giving us ideas to test.

I’ll leave that here for now and let readers explore the volume as it firms up. It only remains for me to thank my co-editors and the various referees as well as of course the authors themselves and the people at the Geological Society for their help with producing this volume and  look forwards to seeing the final printed version.

 

 

  • For the record as this kind of thing has caused consternation among some before, I did not have anything to do as editor with my own authored paper. It was handled entirely independently by the other editors and I had no access or input to the process (and nor did they to their own papers). In a small field like pterosaur research it’s hard if not impossible to find referees and editors who are truly independent, and it’s a bit odd to exclude people who have the knowledge to edit a volume from contributing to it, so this is the best solution. This really is common in lots of specialist volumes, but it’s worth noting that it was done as transparently and ethically as possible.

 

Buried Treasure – Jordan Mallon

What is my least appreciated paper? That’s an easy one:

Mallon, J. C., and Evans, D. C. 2014. Taphonomy and habitat preference of North American pachycephalosaurids (Dinosauria, Ornithischia). Lethaia 47:567–578.

This is a paper that I co-wrote with my good friend and colleague, Dave Evans. It’s been published for nearly three years now, and has garnered only two citations—both of which are from Dave and me! Despite this, the paper effectively debunks a widely held meme that North American pachycephalosaurs were mountain dwellers, à la big-horned sheep. This is an idea that gets a lot of play in both the popular media and textbooks (including some that have come out even after our paper was published).

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See what I mean? The belief that North American pachycephalosaurs lived in the mountains is all over the place!

 The idea for the project came to mind shortly after I started my postdoc at the Canadian Museum of Nature in 2013. I was reading some papers by my predecessor here, Charlie Sternberg, and repeatedly came across this notion of his that North American pachycephalosaur skull domes tend to be well worn, “as if they had been rolled down a stream” (C. M. Sternberg. 1970. Comments on dinosaurian preservation in the Cretaceous of Alberta and Wyoming. National Museums of Canada Publications in Palaeontology 4:1–9). For Charlie, the implication was that these pachycephalosaurs must have lifted in upland—even intermontaine—environments, and not in the ancient coastal plain environments where their skull domes are typically found. Others have run with the idea since then.

But was Charlie right? Are these pachycephalosaur domes typically water-worn? No one had done the hard work of looking over the original fossil material to find out. Fortunately, most of the domes that Charlie collected were available for examination at the Canadian Museum of Nature. Dave and I further supplemented our dataset with domes from the Royal Ontario Museum and the Royal Tyrrell Museum of Palaeontology. In all, we had a respectable dataset of 187 domes, which is nothing to sneeze at (particularly if you’re a dinosaur palaeontologist). Without going into the nitty gritty of how we assessed dome wear (you can read the paper for that), suffice it to say that we found that domes were not typically worn. We also found that dome wear does not correlate with distance from their presumed origin in the Rocky Mountains, nor are pachycephalosaur remains relatively more abundant in intermontaine deposits, which we could expect if the critters lived there.

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North American pachycephalosaurs almost certainly lived in the ancient coastal flood plains where we find their skull domes today. Image credit: Brett Booth.

Dave and I took this to mean that pachycephalosaurs must’ve been living where we find their remains: in the low-lying coastal floodplains, alongside the more common hadrosaurids and ceratopsids. It’s an important first step in understanding things like dinosaur community ecology and beta diversity. It’s also a good reminder that taphonomic processes like erosion can actually inform our understanding of the habits of fossil organisms, and are not simply information-destroying by nature.

If anyone wants a copy of the paper (which is behind a paywall), please fire me off an email at jmallon AT mus-nature.ca.

 


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