A Paleontology-Specific Impact Factor for PLoS ONE

The threads at SV-POW! are hopping right now, particularly with one commenting on open access in Journal of Vertebrate Paleontology. One question that came up is how much, if at all, the impact factor of PLoS ONE (4.411 for 2010) indicates the reach of paleontology papers in that journal. In other words, if PLoS ONE just published paleontology papers, what would its IF be?

Naturally, I had to calculate it out. I used the standard IF formula, and looked just at citations in 2010 for papers published in 2008 and 2009. Citation counts were derived from Web of Science, which is linked to from each individual article at the PLoS ONE website. Articles under consideration from 2008 and 2009 were harvested from the PLoS ONE Paleontology Collection; one or two articles in there were only tangentially paleontological, but I kept them in anyhow just for consistency.

I calculated a "paleontology IF" of 3.317 for 2010 - a little lower than 4.411 for the overall journal but still higher than in other more field-specific publications. So, not too shabby.

This omits the issue of whether or not impact factors are worth anything, but I won't delve into that here. Love it or loathe it, we scientists still like to talk about IF!

PLoS ONE 2011 - Final Round-Up

Back before the new year, I reviewed all 17 of the new fossil taxa that were published in PLoS ONE during 2011. Here, I look at the general trends for paleontology in the journal, both last year and over its entire history.

Topics and Biases

Paleontological Topics in PLoS ONE, 2011

The chart above shows the general topics covered by PLoS ONE papers in paleontology during 2011 (for those of you adding the numbers, a handful were counted in two categories). Just as for new taxa, there is a major skew towards archosaurs. Much as I love dinosaurs, we really need to get a broader diversity of taxonomic coverage. Part of this is probably the result of different cultures of publishing among different groups of specialists - dinosaur workers are comfortable with PLoS ONE, whereas trilobite workers aren't. We need some pioneers in invertebrate paleontology, paleoicthyology, and elsewhere.

The Big Picture
By my count, there were around 65 paleontology-related articles published in PLoS ONE last year (2011). This is up from 39 articles in 2010, and reflects a continuing increase since PLoS ONE was founded in 2006.

Trends in Number of Paleontology Papers at PLoS ONE

Compare this count of 65 for PLoS ONE with 95 papers in Journal of Paleontology and 120 papers in Journal of Vertebrate Paleontology during 2011. PLoS ONE is still smaller than some "conventional" journals, but I think it is safe to say that it may overtake these alternatives in annual volume within the next year or two. Whether or not this is a good thing for PLoS ONE and paleontology is another question - if the quality of the papers submitted to the journal as well as the editing process can be maintained (or improved where necessary), perhaps yes.

Many paleontologists clearly are warming up to the idea of PLoS ONE. It is tough to know what factors are behind this - whether it's availability of high-resolution color figures, cost-effective outlets for lengthy papers, frustration with "conventional" journals, the impact factor, broader acceptance of open access, or something else altogether. Other paleontology journals - and paleontological societies that publish their own journals - would be wise to see what they can do to match or improve upon the attractive points of PLoS ONE. As much as I love PLoS ONE, the last thing I want is a publishing monoculture. Unless others journals adapt, though, this may be the result.

The oldest Eucalyptus in the world - from South America! Modified after Gandalfo et al., 2011

[note: although I am a volunteer editor at the journal, this post reflects only my personal opinions]

New Fossil Species of 2011 - A PLoS ONE Retrospective

What do sauropods, primates, crabs, cats, and crocodiles have in common? They're all animals in the fossil record that had new species named in PLoS ONE this year!

Chela (claw) of Geograpsus severnsi, from Paulay & Starmer, 2011

As 2011 winds down, I'm going to devote two posts to some navel-gazing at paleontology in the online, open access journal PLoS ONE. PLoS ONE really has been a ground-breaking publication, partly responsible for spawning the term "megajournal" as well as inspiring clones from the very publishers who invested some effort over the past few years in downplaying the worth of the PLoS ONE publishing model.

[Note before we continue: Although I do have an "official" volunteer role as one of the academic and section editors for the journal, any opinions in this post are entirely my own.]

Skull of Arenysuchus gascabadiolorum, from Puértolas et al., 2011

In any case, let's start our 2011 retrospective with a look at some of the new taxonomy that appeared this year. 17 new species of extinct organism were named on the "pages" of PLoS ONE this year, but these were not by any means distributed evenly across the tree of life.

Five out of 17 were mammals, only one was a non-vertebrate (a lonely, recently extinct land crab from Hawaii), and three - THREE!!! - were sauropodomorph dinosaurs. What kind of crazy world is this where sauropodomorph taxa outnumber crocodylimorphs, and arthropods? Dinosaurs as a whole did quite well, with seven new non-avian dinosaurs gracing the HTML code of PLoS ONE.

New Fossil Taxa Named in PLoS ONE - 2011
Arenysuchus gascabadiolorum (crocodyliform)
Boutakioutichnium atlasicus (theropod footprint)
Gaudeamus aslius (rodent)
Gaudeamus hylaeus (rodent)
Geograpsus severnsi (crab)
Kawichthys moodiei (chondrichthyan)
Khoratpithecus ayeyarwadyensis (primate)
Leonerasaurus taquetrensis (sauropodomorph)
Leyesaurus marayensis (sauropodomorph)
Linhevenator tani (troodontid)
Lycophocyon hutchisoni (carnivoramorph mammal)
Panthera zdanskyi (felid)
Paravipus didactyloides (theropod footprint)
Pissarrachampsa sera (crocodyliform)
Talos sampsoni (troodontid)
Tapuiasaurus macedoi (sauropod)
Tonsala buchanani (bird)

In 2012, I would love to see the following trends:

• An expansion in the number of new taxa published in PLoS ONE (assuming that high scientific standards are maintained - no junk taxa, please).
• Greater diversity in the taxonomic groups represented. Archosaurs are cool and all, but where are the plants? Where are the brachiopods? This will probably just take time, and perhaps a pioneer in each field of study to raise awareness of the journal. I first seriously considered publishing in PLoS ONE because a high-profile dinosaur worker published there, and I suspect other folks in other fields have similar thoughts.
• More authors taking advantage of the format of PLoS ONE when submitting their new taxonomy. With few or no practical limits on figures (color, size, number) and text, every new description could potentially (and should, with few exceptions) get the monographic treatment. I am happy to say that most authors did just this, but there is always room for improvement!

Skull of Tapuiasaurus macedoi, from Zaher et al., 2011

In the next post: PLoS ONE is now a major force in paleontological publishing. What were the overall trends in 2011? What might the future bring?

Life After Death At Yellowstone: An Interview with Josh Miller

In my last post, I introduced a ground-breaking study recently published in PLoS ONE, that shows how we can infer long-term trends in animal populations just from their bones. This work has big implications for ecology, conservation, and public policy, and is also a really neat piece of science. For this post, I talked to the author of the study, Josh Miller, about his work and some of the tidbits that didn't make it into the paper.

Yellowstone NP gets a lot of visitors, and you surely must have had some interactions with them during your fieldwork. How did they react to what you were doing?

JM: I work in areas that are generally well off trail and in places most Yellowstone visitors just don't see. Over the years, there are have been very few times when tourists actually ever saw my teams conducting our bone work. Most of the time, conversation with the public occur in the evenings back at camp. We generally use the public campgrounds for our homebases and my research will often come up in conversation with tourists. When folks learn what my teams and I are up to, they are always very interested and ask lots of questions. Our National Parks are an important resource, and I think people like to be reminded of their biological and scientific value. At the same time, I think it gives folks a way of looking at Yellowstone in a new and exciting way. I know lots of people who talk to us one day and keep an eye out for bones the next.

Miller studying bone survey data sheets on Northern Range, Yellowstone National Park. Photo by Scott Rose.

You looked at hundreds of bones during your survey. Was there any particular specimen that stuck out in your mind? What about it was interesting?

JM: I looked at over 20,000 bones during my work in Yellowstone. And you are right, there are a few that really stand out. Some of the most memorable bones are those of animals with severe bone maladies. In some individuals we found severe arthritis or broken bones that didn’t heal properly. Other memorable bones include rare and unusual species. One of the most exciting finds was the skull of a mountain lion. We just stumbled upon on it one afternoon walking from one transect to another. This beautiful rounded huge cat skull just lying in the grass staring up at us –a rare and amazing site.

This paper focused on bones from large animals, but surely there are a lot of small animal bones out there too - rodents, bats, rabbits, etc. Do you think they would show a similar correlation over time between abundance in life and death? Or are the taphonomic effects too different between large and small animals to expect the same pattern?

JM: Stay tuned! I kept careful attention to the bones of the small mammals we found. My bone survey teams were amazingly good at finding bones of all shapes and sizes (from bison skulls to limb bones of squirrels). One of the challenges, unfortunately, is the lack of high-quality data on the living populations in Yellowstone. One thing I'll say at the moment, however, is that the record of small-bones is surprisingly rich and diverse on the Yellowstone landscapes.

I see that you used the open source stats program R to do your data analysis. Was this something you picked up just for your dissertation work? Why did you choose R over some of the other commercial packages that are out there?

JM: I was introduced to R during the early days of my graduate work. R is a very powerful statistics language, in part, because of the large community of scientists and academics that use R and contribute to its ever-expanding utility. Another reason I use R is that I can completely control all aspects of the analysis. In canned programs, much of the analysis sits under a black box and uncovering exactly how the data were analyzed can be very difficult. But most of all, R just fits how I do science.

Thank you for your time, Josh!

Citation

Miller, J. (2011). Ghosts of Yellowstone: Multi-Decadal Histories of Wildlife Populations Captured by Bones on a Modern Landscape PLoS ONE, 6 (3) DOI: 10.1371/journal.pone.0018057

Note: I'm an academic editor at PLoS ONE, but had no role in the handling of this paper.

Life After Death at Yellowstone

Taphonomy - the study of what happens to an organism after it dies - is integral to reconstructing the past. Perhaps the most important lessons come in inferring ecological interactions. Did that group of animals live and die together, or were they jumbled long after death? Were all of those shark teeth with the plesiosaur bones from a feeding frenzy, or just a fluke of currents? How closely does a set of fossils represent the relative abundance of the different species during their lifetime? Such examples are numerous, and thus we commonly think of taphonomy as a study in deep time. This is certainly true, but also certainly incomplete. In fact, some of the most ground-breaking taphonomic work has been done in contemporary ecosystems. Kay Behrensmeyer, for instance, has spent decades studying bone accumulations in Kenya, and a 1927 work by Johannes Weigelt (complete with photos of dead cattle) is still considered a classic.

A new study by paleontologist and taphonomist Josh Miller, just published in PLoS ONE, shows some of the great insights that can arise from looking at taphonomy in modern settings. Josh and his field assistants trekked through Yellowstone National Park (one of the western USA's oldest and best-known parks), cataloging the identity and physical condition of every animal bone sitting out on the surface (an elk skeleton from the project is shown at right; photo courtesy of and copyright Josh Miller). Using these data, Josh found that you can actually infer the major ups and downs of animal populations from their old bones. This is quite exciting, not just from a gee-whiz factor, but because it may be possible to infer population trends for areas where historical surveys are absent or spotty. Such data are important not only for ecologists, but for informed public policy. It sounds magical, so how was the study done?

Based on other studies (in combination with radiometric dating), it's known that bones in excellent condition usually came from animals that died only recently, whereas bones in crummy condition are from animals that died longer ago. By using the condition of the bones as a proxy for time since death, Josh estimated how long the various bones of various animals had been around. Then, based on the bone ages, he estimated the relative population of each type of animal a given number of years ago. We have very good wildlife census data for Yellowstone, and it turns out that estimates from the bones match the "real" values quite nicely. Boom years for animals (such as elk) mean lots of bones going into the system, bust years mean few bones, and these trends shows up in bone surveys.

You can read all about it at PLoS ONE, or here, here, and here. I recently talked to Josh to get a few behind-the-scenes tidbits. Stay tuned for the interview later today! [update: now posted here]

Citation
Miller, J. (2011). Ghosts of Yellowstone: Multi-Decadal Histories of Wildlife Populations Captured by Bones on a Modern Landscape PLoS ONE, 6 (3) DOI: 10.1371/journal.pone.0018057

Note: I'm an academic editor at PLoS ONE, but had no role in the handling of this paper.

Nedoceratops - Random Thoughts

The last two posts here have focused on my most recently published paper, fully describing the skull of the horned dinosaur known as Nedoceratops hatcheri and critiquing the hypothesis that it, along with Torosaurus latus, is simply an older individual of what we call Triceratops. Because I've already talked about the science of the paper, and some collegial interactions, I'm going to spend this final post in the series talking about a few odds-and-ends that just didn't fit anywhere else. Most of these are little windows into the process behind the paper - from writing to review to revision. And we'll start with. . .

Open Source Composition

I'm proud to say that every single step of the authoring process for my paper happened in open source software. I wrote the manuscript in OpenOffice.org Writer, formatted most of the references in Zotero, did initial image editing (contrast adjustment and background removal) in GIMP, assembled the figures in Inkscape, and submitted the manuscript through the journal website on the browser Firefox, all of which were running on various releases of Ubuntu. Score one for open source software (and open access publishing)!

On Organizing the Paper

I'm under no illusion that everyone (?anyone?) will agree with my conclusion that Nedoceratops is a valid taxon. In fact, I'm quite accepting of the possibility that I may be wrong. But even if this is the case, I still want my paper to be useful. So, I made my best effort to separate data from interpretation in the description section of the paper. Of course, I couldn't be completely successful on this point - after all, I had to compare Nedoceratops with Triceratops and Torosaurus (the most likely candidates for synonymy) - but I like to think that I mostly achieved my goal. If nothing else, I have pretty pictures. And. . .

Speaking of Pictures

My figures went through some pretty drastic changes during the evolution of this paper. In the first round of reviews, it was pointed out that in the text I kept referring to various structures illustrated in the figures, but only a ceratopsian geek could figure out what I was talking about.

For example, we have this lovely sentence:

The narial strut is inclined rostrally towards the dorsal end of the element, and enough original bone surface is preserved to indicate that a posterior internarial flange did not project from the caudal surface of this structure (Figure 4).

My original Figure 4 looked like this:

The photo is relatively pretty, but only a die-hard ceratopsian nerd could locate the narial strut or know where to look for a posterior internarial flange if such a thing even existed in this animal. So, for my next iteration I added some labeling:

Of course, all of the abbreviations are explained in the caption (not shown here). "ns" refers to the narial strut I was talking about above. Finally, the editor mentioned that I should do a better job of indicating the "cpf" (canal at the edge of the premaxillary fossa). It wasn't just at the tip of the arrow, but over a somewhat broader area. Thus, that brings us to version 3:

This, with the extra arrows showing the position of the canal, was the version that appeared in the paper.

If I learned anything from this experience, it was about the importance of good labeling and interpretive drawings for non-expert readers. Most of the labeled interpretive drawings alongside photographs (with the exception of parts B and D in Figure 1) were added at the direct request of the editor. Looking at the end product, this addition was a major improvement to the paper. Of course, I must also admit that having relatively unlimited space in an online journal allows this luxury!

Editorial Ethics

It's probably not a surprise to many of you that I am a volunteer academic editor at PLoS ONE. And those of you who have been paying attention probably noticed that the Nedoceratops paper was just published in that very same journal. This sounds pretty problematic on the face of it.

Thankfully, PLoS ONE has pretty strict editorial controls when one of their own editors submits a paper (in addition to a competing interests policy that covers this and similar situations). My experience as a submitting author was exactly the same as for any other author. Once the "submit" button was pressed, I had to wait just like everyone else. I couldn't control which editors handled it, who reviewed it, or even have a sneak peek at the reviews on-line. In other words, the system functioned exactly as it should.

My authorial feet were held to the fire by Leon Claessens, the handling editor for my submission. Leon, in my opinion, did a very professional job and didn't let me get away with anything (even sending the manuscript back to me a second time for a few last corrections and improvements). The reviewers - Michael Ryan and Peter Dodson - also did their jobs (in my opinion). And, as mentioned in my last post, comments by John Scannella and Jack Horner offered additional constructive feedback.

One thing I really like about PLoS ONE is that my competing interest - as an editor at the journal - is stated up-front in the paper. Although it's somewhat scary seeing it there, I think such notices are certainly appropriate.

Final Thoughts

It's nice to finally have this paper out there - these ideas have been floating around in my head for awhile, and I've always had a secret desire to be the person to describe Nedoceratops. I'm relatively pleased with the final product (of course, there are always one or two typos that slip through, and why couldn't some of the figures in the PDF have been bigger?), and look forward to the discussion that this paper generates. Thank you to all who helped out (see the acknowledgments for a comprehensive list)!

Nedoceratops - A Full Description at Last

Every group of animals has at least one notable yet neglected specimen. In horned dinosaurs, a particular example is a large skull at the Smithsonian discovered in Wyoming during the closing years of the 19th century. Unfortunately, this specimen has suffered a twisted and sometimes tragic history.

The skull of Nedoceratops hatcheri, modified from Farke 2011

The collector of the fossil, John Bell Hatcher, wrote a paper about the specimen, but died before he could publish it. So, the task fell upon Yale's Richard Lull, who gave this nearly complete skull the name of Diceratops hatcheri. It looked much like a Triceratops (the famous three-horned face), but differed from the standard "Trike" in having a tiny nose horn, several holes in the frill, and a handful of other characteristics. Later on, other scientists decided that these differences were probably just the result of individual variation, injury, or other illness. So, Diceratops became just another Triceratops to most workers (a 1986 paper by John Ostrom and Peter Wellnhofer was influential in this regard). Still, there wasn't unanimity in that thought - Cathy Forster, for one, published the opinion (in 1996) that Diceratops was indeed distinct from Triceratops.

Nedoceratops hatcheri, as restored by Nobu Tamura.

In 2000, the skull (which was on exhibit at the Smithsonian) was damaged when some rowdy museum visitors crashed through a barricade and broke the snout. Fortunately, the museum's preparators were able to fix it. As if to add insult to injury, it turned out that the name Diceratops wasn't unique. A German entomologist (coincidentally named Förster) had applied the name to an insect way back in 1868, so a new name had to be found for the dinosaur. Unfortunately, this didn't happen in the most organized way. Two researchers independently published the replacement names of Diceratus (in 2008) and Nedoceratops (in 2007). The second one, although less elegant (in my opinion), had priority because it was published first.

But wait - there's more! The story of Nedoceratops took an interesting twist last year, when John Scannella and Jack Horner suggested that it represented a life stage of Triceratops, halfway through its transformation into Torosaurus (see the figure below). This was not an evolutionary transformation, of course, but ontogenetic (one that happened as an individual animal got older). So, our three animals - Triceratops, Nedoceratops, and Torosaurus - were all just the same thing! Such revelations happen frequently in paleontology. For instance, the duck-billed dinosaur Procheneosaurus turned out to be young Corythosaurus, Lambeosaurus, Hypacrosaurus, and the like. But, not all horned dinosaur experts are convinced that this was what was going on with Nedoceratops and Torosaurus.

From left, life restorations of Triceratops, Nedoceratops, and Torosaurus (all modified after originals by Nobu Tamura). The arrows indicate the relative age of each animal, as proposed by Scannella and Horner. If they all are the same thing, Triceratops is the "young" life stage, and Torosaurus is the "old" life stage, with Nedoceratops being a transitional form. The big question: are these the same animal, or different species?

Named, renamed, renamed again, broken, pieced together, and declared invalid, Nedoceratops has had a checkered past. Yet, the skull has never received a fair treatment in the scientific literature. I'm not just talking about people's opinions of the specimen. Instead, I'm talking about a full description.

Descriptions - detailed accounts of a specimen's characteristics - are the data upon which much of paleontology relies. But, the skull of Nedoceratops was never fully described. A few paragraphs have been written about it here or there, but it turns out that many aspects of these were inaccurate or incomplete. Given the controversy over this skull, an accurate and complete description of the animal was particularly important. So, I set out to fix the situation. In my recent PLoS ONE paper, I published the first comprehensive description and illustration of Nedoceratops hatcheri.

At risk of boring you readers with endless details, I'll just mention a few minor points. For instance, it turns out that many of the early drawings of the specimen were inaccurate (missing bone was shown as present, for instance). I was able to correct these errors, and talk about areas of the skull that were well-preserved but never discussed in the literature before. My paper also includes detailed and never-before-published photographs of the skull in various views, which I hope will be useful for folks who can't see the skull first-hand.

Finally, and probably of the broadest interest, I go out on a limb and say that Nedoceratops hatcheri is a unique species - not the same as Triceratops or Torosaurus. In my opinion (and it is but an opinion), there are just too many features that are different between these animals, and few features can be chalked up to injury or growth changes. Will this opinion stand the test of time? Maybe, maybe not. My opinion on the validity of Nedoceratops is probably the most tentative conclusion I've ever published, so my feelings won't be terribly hurt if I turn out to be wrong (although of course, I'd rather be right).

And what about the idea of Triceratops being a junior version of Torosaurus? I argue that Torosaurus and Triceratops are indeed distinct species, not just old and young versions of the same animal. Why is this?

• Triceratops and Torosaurus have vastly different numbers of bony bumps - called epiparietals and episquamosals - on the edges of their frills. If Torosaurus is the younger version of Triceratops, this means that Triceratops added a bunch of these bumps to the frill during growth. Yet, there is no good evidence that any other horned dinosaur did this.
• Triceratops has a solid frill, and Torosaurus has big holes in its frill. In all other horned dinosaurs we know (such as Protoceratops and Centrosaurus), if adults have holes, the young ones have holes. Thus, it doesn't make a lot of sense that Triceratops/Torosaurus would only add these holes when it got really big. [of course, I will admit that just because something doesn't make sense doesn't mean it couldn't happen - just that it is much less likely]
• It was previously claimed that there were no good examples of "young" Torosaurus. But, a skull at Yale (collected by Hatcher, the same person who discovered the Nedoceratops skull) fits all of the characteristics of a young animal. Its skull sutures are all open, or unfused, and the bone has a smooth texture typical of young dinosaurs. In my mind, this is probably the best evidence that Torosaurus is not a grown-up Triceratops.

Undoubtedly, many other paleontologists will have something to say about these issues. Some will agree, some will disagree, some will show parts of my paper are incorrect, and others will present more supporting data (at least I hope, on all counts). I suspect the next few years will feature much, much more discussion on these fascinating horned dinosaurs!

Coming Up: It is safe to say that I have had more fun with this project than with anything else I've done recently. Why is that? In part, it's been due to some very stimulating discussions with John Scannella and Jack Horner, who recently published the "Toroceratops" hypothesis. See my next post for more!

Citations

Farke, AA (2011) Anatomy and taxonomic status of the chasmosaurine ceratopsid Nedoceratops hatcheri from the Upper Cretaceous Lance Formation of Wyoming, U.S.A. PLoS ONE, 6 (1) DOI: 10.1371/journal.pone.0016196

Forster CA (1996) Species resolution in Triceratops: cladistic and morphometric approaches. J Vertebr Paleontol 16: 259–270.

Förster A (1869) Synopsis der Familien und Gattungen der Ichneumonen. Verhandlungen des Naturhistorischen Vereins der Preussischen Rheinlande und Westfalens 25: 135–221.

Hatcher JB (1905) Two new Ceratopsia from the Laramie of Converse County, Wyoming. Am J Sci, series 4 20: 413–422.

Mateus O (2008) Two ornithischian dinosaurs renamed: Microceratops Bohlin, 1953 and Diceratops Lull, 1905. J Paleontol 82: 423.

Ostrom JH, Wellnhofer P (1986) The Munich specimen of Triceratops with a revision of the genus. Zitteliana 14: 111–158.

Scannella JB, Horner JH (2010) Torosaurus Marsh, 1891, is Triceratops Marsh, 1889 (Ceratopsidae: Chasmosaurinae): synonymy through ontogeny. J Vertebr Paleontol 30: 1157–1168.

Ukrainsky AS (2007) A new replacement name for Diceratops Lull, 1905 (Reptilia: Ornithischia: Ceratopsidae). Zoosystematica Rossica 16: 292.

Citation Format Wars

Over at SV-POW!, Mike Taylor recently addressed the issue of how to format in-text citations. Writing in his inimitable style, he makes the case that PLoS ONE is simply doing it all wrong; the majority of commenters there have agreed. I posted a lengthy comment there, but realized that it would be appropriate to revise and republish those thoughts here too.

First off, let's have a quick recap of the issue. When writing a scientific paper (or any paper, for that matter), it is essential to credit the sources of information and ideas. Not only does it allow the reader to learn more about the topic, it's the ethical thing to do. Rather than a simple reference listing at the end of the paper, most scholarly works also reference the relevant works within the text. This is called an in-text citation, and allows the reader to know precisely which information was associated with which author.

Two Worlds
Two styles of in-text citation dominate the scientific literature. The first of these is author-year, which looks something like this: (Farke, 2010). The second is numbered, which looks like this: [1]. This number then refers to a specific bibliographic entry at the end of the paper. Many variants of each style exist.

PLoS ONE uses numbered citations, in common with many other high profile journals (such as Nature), and in marked contrast to most of the paleontological, geological, and anatomical literature (such as Journal of Vertebrate Paleontology, The Anatomical Record, Geology, and others). The SV-PoW! post, of course, argues that the numbered format is vastly inferior to the author-year format. Let's boil the argument down to its essentials, and delve into the pros and cons of both formats in more detail.

Two essential reasons are given for why the author-date format are preferable: 1) ease of reading for authors familiar with the literature; 2) paleontologists don't like it. PLoS ONE thus chose a numbered reference format simply because they wanted to copy the glamour magazines. Do any of these arguments hold up?

Advantages of Author-Year (and disadvantages of Numbered)
Of course, there are some significant advantages to the author-year format. These include:

1. It's easy for readers who are familiar with the literature to know exactly what's being discussed. If I quote from my 2010 JVP paper on ceratopsian sinuses, "Less detailed descriptions have been published for other chasmosaurine and some centrosaurine ceratopsids (e.g., Gilmore, 1917; Lehman, 1990; Sampson, 1995; Sampson et al., 1997)," a long-time ceratopsian worker will know right off the top of her or his head that I'm talking about the Gilmore Brachyceratops monograph, Tom Lehman's paper in the Dinosaur Systematics volume, Scott Sampson's description of the Two Medicine centrosaurines in JVP, and the ZJLS paper with Scott, Michael, and Darren. I see pages from those papers when I close my eyes, and I could almost write the citation for each of them off the top of my head.
2. You don't have to flip back and forth between the main text and the reference list. For the ceratopsian expert described above, there's no need to waste time skipping around the paper (or PDF). It's just easier.
   
3. It helps readers new to the field to become familiar with the major names and papers. See the names "Wedel," "Taylor," "Wilson," "Curry-Rogers," and others often enough, and you probably have a good picture of a few of the major recent workers in sauropods.
   
4. It's easier for authors to keep their references straight. When writing and revising without use of a citation manager, the numbered system can get very unwieldy. If you add a reference in the middle of the paper, you not only have to renumber the entire bibliography after that reference, you also have to change the numbers within the manuscript itself. Miss one, and your readers are going to be grumpy when the number and citation don't match up.
5. It's familiar to the paleontological community. As mentioned above, "It's Got What Paleontologists Crave."
   

Disadvantages of Author-Year (and Advantages of Numbered References)
As you might have guessed, there are some disadvantages, too:

1. The author-year format is helpful only if you are already familiar with the relevant literature. Otherwise, you're still in the game of flipping back and forth to the reference section. Anticipating that most of my readers are savvy to vertebrate paleontology, but not to the latest in tectonics, contrast my above example in point 1 with this example (Najman et al., 1997, Geology 25:535-538): "Why is this so, as crustal thickening and metamorphism are thought to have occurred by this time (Frank et al., 1977; P. Zeitler in Hodges and Silverberg, 1988; Inger and Harris, 1992; Searle, 1996, and references therein; Vanny and Hodges, 1996)?" Although I understand the meaning of the sentence, the names and dates have absolutely no meaning to me, other than to help me find the appropriate citation in the back. I'm not familiar with that literature, so I'm annoyed by the extra text.
   
2. Not every reader wants to become an expert on a given subspecialty. Believe it or not, I may not be reading a plate on Indian tectonics (or sauropod vertebrae) because I want to become an expert on said subject. Let's say that I'm chasing the above-mentioned example from Najman because I want to know the context for some fossils I found in a format described in that paper. I just want the bare minimum of info, and I don't care about Frank, or Zeitler, or Hodges, or Silverberg, or Inger, or Harris, or Searle, or Vanny. Sure, maybe I'll chase some of those references for alternate opinions, but once that's done the names will probably never cross my mind again. This leads to the next point. . .
3. The author-year format clutters the text. I'm not the first person to state this, and I'm not the last. By editing my ceratopsian quote above, you now get: "Less detailed descriptions have been published for other chasmosaurine and some centrosaurine ceratopsids [1-4]." Try the same with the Najman quote. Much shorter and more easily readable. A comment on the SV-POW! post by Zen Faulkes gives some more nice supporting opinions.
4. Most of the rest of the scientific world uses numbered citations. I think people are giving Science and Nature a little too much credit for driving the numbered citation game. Yes, they certainly are the most visible journals to those of us in paleo/geo/zoological sciences, but that's a rather myopic view. I did a quick survey of the other 99 percent of the scientific literature, and numbered citations simply dominate. Even arXiv - the epitome of digital presentation with no real standard format - has a vast majority of papers with the [1,2,3] style (in fact, the only counterexamples I found were in a handful of biologically-oriented papers). The medical literature (medically oriented papers are the great majority of PLoS ONE submissions), computing literature, physics literature, etc., most often use numbered citations. Let's face it - paleontologists are not the biggest fish in the sea. It doesn't mean we're wrong or can't change things, just that it's a very uphill battle.

Closing Words
So, I have to say that the arguments for author-year and against numbered references are not as simple as one might hope. Major advantages and disadvantages characterize both formats. In the end, I suspect much of it comes down to "what we were born into." I like the author-year format because that's all I've ever known. My spouse, who is a physicist, surely thinks otherwise, but then again all she has ever known is the numbered format. She also thinks paleontologists are silly because we don't use LaTeX (and good luck getting that instituted, no matter how easy it would make things for us).

Interestingly, I came into this with a strong preference towards the author-year citation format, but after thinking about it I'm not sure that numbered citations are the Great Evil that they have been made out to be. What are your thoughts?

Update: The above-mentioned Zen Faulkes has a post strongly coming down on the side of numbered references. He argues that numbered references decrease overall manuscript length, greatly improve readability, and level the playing field for both readers and cited authors. The last argument is particularly novel, and strikes at the heart of the true purposes of citations. I'm not sure I totally agree, but it's definitely food for thought. [12 January 2011]

(As an interesting side-note, the author-year referencing style may be so common in the paleontological and zoological literature because of a historical accident - the format was apparently invented by a Harvard zoologist, and spread throughout the zoological part of the literature. I suspect the weight of the Harvard name didn't hurt.)

Disclaimer: Although I am a volunteer editor at PLoS ONE, this posting is written strictly as my private opinion.

Thank you to the many commenters at the SV-POW! blog, whose thoughts inspired this post.

Back to the Late Jurassic, With Chris Noto

If you ask the average person to imagine the Age of Dinosaurs, odds are quite good that they might envision a scene from the Morrison Formation. This Late Jurassic-aged (156 - 147 million year old) rock unit of the western United States has given us such dinosaur greats as Stegosaurus, Apatosaurus, Allosaurus, and more. Many of these animals are known from exquisitely-preserved, complete skeletons - and thus their anatomy has been described in pretty ridiculous detail. The functional morphology (how these animals moved, breathed, ate, and fought) has also gotten a lot of attention. But, this only tells us about the individual lives of the organisms. To really understand their world, we need to think bigger.

Chris Noto, my friend and academic brother (we had the same Ph.D. advisor), has devoted his scientific career to a big-picture understanding of dinosaur ecology. He has a special place in his heart for the dinosaurs of the Morrison Formation, and has been chipping away at their ecology for quite awhile now. Thus, it was really exciting to see his recent co-authored paper in PLoS ONE, about that very topic. Also of note was that this paper served as Chris's contribution to the 2009 Paleo Project Challenge!

Chris was kind enough to offer a little behind-the-scenes look at his project and the research results. I hope you'll find it enlightening!

How did you get the idea for your project?
Well, this involves going back a ways. I have always been fascinated by extinct organisms, particularly what they were like as living, breathing individuals in their environment. As an undergraduate at the University of Chicago I had the privilege of working with two really great scientists: Paul Sereno and Fred Ziegler. Paul is a well known paleontologist who has worked all over the world. Fred’s work was responsible for many of the paleogeographic and paleoclimate maps used today. Working with Paul got me thinking about how dinosaurs varied over space and time; working with Fred introduced me to global climate patterns and changes in continental arrangement.

Once I got to graduate school at Stony Brook University I was taught the fundamentals of ecological theory. I started formulating an idea for looking at variation in dinosaur communities (the collection of all the different types of organisms that live in an area) and how those differences may be related to climate, but wasn’t sure how to approach it. Enter my good friend (and coauthor) Ari Grossman, who suggested applying this method, called Ecological Structure Analysis, commonly used in the study of fossil mammals. After some discussion on the appropriate way to adapt this method to the type of information available for dinosaur fossils, we agreed to work together on this project.

What was the most challenging part of writing the manuscript?
Like many papers, this one languished half done for many years. This was a side project of ours, and unfortunately our dissertation research had to come first. Every time I started working on it again I would realize that the data needed to be changed or updated, and this would sometimes change the results and our interpretation. I am a stickler for details and want to make sure all the data are as accurate as possible. But this project was simply too cool to let go. Once I graduated I decided to finish this manuscript as a first priority. It actually didn’t take too long after that once I put my mind to it; in the end I think that the paper was all the better for it. I learned a lot in the meantime, which contributed to making it a stronger manuscript. The hardest part by far though was actually submitting it to PLoS ONE for consideration. No one likes to be rejected, especially after putting so much work into a project! But this is the way the peer-review system works.

I noticed that you used the program PAST for your statistical analyses - how did you decide on that program? Were there any particular challenges to using this software?
I was attracted to PAST because it could perform the analyses I needed to do without a lot of unnecessary complication. Best of all, it was free, and I was a poor graduate student at the time. Most commercial statistics programs are expensive and difficult to use. PAST has a relatively simple interface and the results are easy to interpret, which is important. The major challenge with using PAST is in data management. If the data are not arranged in exactly the right way the analysis will not work correctly. Therefore it requires arranging the data first in a program like Microsoft Excel, and then copying and pasting it into PAST.

What was the most interesting thing you learned while doing your research?
First of all, I wasn’t sure what to expect when I started doing this research. No one has looked for large-scale patterns like this in dinosaurs before. One interesting thing I learned is that such patterns exist in the fossil record and are preserved over the immense spans of time between when these communities existed and when they were recovered. The most exciting result for me has to be the fact that the proportion of different “ecomorphs”, such as high-browsing herbivores vs. low-browsing herbivores or bipeds vs. quadrupeds, varies with climate. So, we can draw a connection between the climate, environment, and adaptations of organisms living in an area (see figure below). This is no surprise for any ecologist working today, but has not been shown in a terrestrial ecosystem as ancient as the Jurassic (~155 million years ago). This opens up new areas of research into the role climate change plays on the structure of ecosystems over time.

Cartoon showing variation of environment and dinosaur ecomorphs. Drier conditions are on the left, where very large herbivores dominated among relatively sparse plant life. Communities under seasonal conditions are towards the center, and include a greater diversity of feeding modes among increased ground cover. To the right are moister conditions, where smaller herbivores are more prevalent within a more densely vegetated environment. Green=high browser, orange=intermediate browser, blue=low browser, red=ground forager. After Noto and Grossman 2010.

Thanks, Chris! For more about his research, check out his web site.

[Disclaimer: Although I am an editor at PLoS ONE, I had no role in the handling of this paper]

Citation
Noto, C., & Grossman, A. (2010). Broad-scale patterns of Late Jurassic dinosaur paleoecology PLoS ONE, 5 (9) DOI: 10.1371/journal.pone.0012553

Welcome, Hippodraco and Iguanacolossus!

Iguanodonts certainly have been a fertile ground for study lately - for a short summary, check out Darren Naish's excellent posts here, here, and here. Although the European iguandonts (such as the classic Iguanodon) get much of the attention, their North American cousins were also apparently pretty speciose.

Today, a new study headlined by the University of Pennsylvania's Andrew McDonald names two genera and species from the Early Cretaceous-aged Cedar Mountain Formation of Utah - Iguanacolossus fortis and Hippodraco scutodens (pictured below). [full disclosure: I was the academic editor at PLoS ONE who handled this manuscript]

Hippodraco scutodens (left) and Iguanacolossus fortis (right); modified from original artwork by Lukas Panzarin, in McDonald et al. 2010. Scale bar equals 1 m.

Each animal is known from a rather nice partial skeleton, allowing relatively confident phylogenetic placement of the two animals. McDonald and colleagues did a fantastic job describing and illustrating both taxa; all of the known elements are shown in some detail, which will be a huge help for other researchers who may not have easy access to the original material in Salt Lake City. The PDF weighs in at 35 pages, and 39 high resolution figures can be downloaded from the PLoS ONE web page for the paper.

Although there are already three other iguanodonts named from the Cedar Mountain Formation (Eolambia caroljonesa, Planicoxa venenica, and Cedrorestes crichtoni), McDonald lays out substantive morphological and geological evidence for the distinctness of the new taxa. Odds are good that there will be (or are) differing opinions from other paleontologists, so I suspect we're going to be hearing much more about the Cedar Mountain iguanodonts in the near future!

Citation
McDonald AT, Kirkland JI, DeBlieux DD, Madsen SK, Cavin J, Milner ARC, Panzarin L (2010) New basal iguanodonts from the Cedar Mountain Formation of Utah and the evolution of thumb-spiked dinosaurs. PLoS ONE 5(11): e14075. doi:10.1371/journal.pone.0014075

Big Pterosaurs Really Did Fly: Interview with Mark Witton Part II

A new paper in PLoS ONE, by Mark Witton and Mike Habib, re-evaluates claims that big pterosaurs were too big to fly. To make a long story short, multiple lines of evidence suggest that giants like Quetzalcoatlus really did take wing! One of my previous blog posts summarized the paper and featured the first part of an interview with senior author Mark Witton. That part of the interview focused on many of the scientific aspects of the research. Today, we'll highlight some of the other highlights. I think you'll find it illuminating!

This paper has received a fair bit of press coverage. Is there anything about the research that you wish had received more attention?
Our coverage was really good: as mentioned above, we ended up in the most unlikely of places along with getting pieces in much more familiar territory. In that respect, I can’t complain but, at the same time, the press really focused on the quadrupedal launch idea [illustrated at right, with a Pteranodon launching itself in this fashion; figure from Witton and Habib 2010] which, while still quite novel to most, was actually first proposed (in print) by Mike back in 2008. There was a fair amount of press coverage for the idea back then, too. Prior to that, though, both Mike [Habib] and Jim Cunningham, who developed the same idea independently of Mike, had given the idea considerable airing on the Dinosaur Mailing List. Bottom line: this latest paper really isn’t the first to comment on it in any capacity. We talked about it a lot, but we’re definitely not its origin. Still, the press really ran with it, despite the fact that the main thrust of our paper is that pterosaurs and birds are generally incomparable beyond very basic aspects of their flight mechanics, and that previous assumptions that they were had lead to probably incorrect assumptions about their way of life. Their disparate launch mechanisms are a particularly important part of our considerations, but they are only one part of many. It’s no big deal, really, but I’m a little concerned that some people will now associate quad launching with this paper and I really don’t want to steal the thunder away from Mike and Jim: they did the real work on it. I’m sure People in the Know will realise the score, but I’ve already had e-mails about the presentation of the quad launch in our new paper like we proposed it. Tell the world, folks: quadrupedal launch came from Mike and Jim! They’re the real geniuses here!

With you in the UK and Mike in the US, the paper is a very international collaboration. What sort of challenges, if any, were particular to this sort of cross-border work?
Mike and I met up twice during the work on the project at different conferences, but, that aside, we worked entirely through e-mail. Trite as it sounds, the internet is amazing: a project like this would be so much harder and longwinded without it. Throwing drafts of the MS at each other, bouncing ideas around and working on the figures was no sweat at all. We could have revisions done and sent back to each other as fast as we could turn them around. In that respect it was as efficient as working with someone in the same department, if not slightly more so, as meandering chats and tangential fieldwork anecdotes – always a risk of visiting the office of any academic – were largely kept out of our online conversations (we made up for it at conferences, though). The long duration spent putting the paper together, mentioned above, was mainly thanks to my workload with the pterosaur models, not anything to do with working internationally. The paper spent a long time sitting on my desk as my time for writing disappeared amidst a blur of fake fur, bluefoam and acrylic paints. So no, working internationally presented very few obstacles. I’m sure the story would be very different if we were working 20 years ago or so, but, today, you can work with whoever you want, wherever they are without a hitch. Well, assuming they check their in-box regularly, that is.

Thank you, Mark, for an informative interview!

Citation
Witton, M., & Habib, M. (2010). On the size and flight diversity of giant pterosaurs, the use of birds as pterosaur analogues and comments on pterosaur flightlessness. PLoS ONE, 5 (11) DOI: 10.1371/journal.pone.0013982

[full disclosure: I am an editor at PLoS ONE, the journal in which this paper appeared]

Big Pterosaurs Really Did Fly: Interview with Mark Witton

Pterosaurs - winged denizens of the Mesozoic skies - get a bum rap. It's bad enough that their name is smeared by the general public, when animals like Pterodactylus are confused with dinosaurs in the news media and in just about every cheap set of plastic dinosaurs. Lately, some scientists have suggested that the largest of these animals just couldn't fly. Is it true that Quetzalcoatlus (pictured here; image from Wikimedia Commons), with its 10 meter wingspan, had wings that were too narrow, a body that was too portly, and bones that were too weak to support flight? Some of the most recent studies have certainly suggested this!

Yet, extraordinary claims require extraordinary evidence, or at least extraordinary scrutiny. Thus, a study by pterosaur experts Mark Witton and Mike Habib takes a close look at the idea of super-lame flightless giant pterosaurs. Using new body mass estimates, revised reconstructions of the wing dimensions, bone strength calculations, and many other lines of evidence, Mark and Mike argue that even the biggest Quetzalcoatlus could fly after all.

This paper, published in PLoS ONE [full disclosure: I am an editor for this journal], has been featured all over the mainstream news media and blogosphere. For a slightly different take on the matter, I decided to go straight to the source. Mark Witton (pictured below; thanks to Mark for the picture, copyright him) was kind enough to answer a few questions about the study - not just on its methods, results, and conclusions, but also on some of the behind-the-scenes doings that led up to this work.

I've split this interview into two parts. For starters, we'll talk about the genesis of the paper, and some of its major findings.

How did this study come about? Did any particular event spur you and Mike [Habib] into working on this issue of flight in giant pterosaurs?
I reckon a paper like ours has been a long time coming, really. There’s been a lot of talk in recent years that pterosaurs may not be what Greg Paul termed ‘ultralight airbeings’, and numerous blogs and internet forums have responded with comments what this may mean for their flight dynamics. It was only a matter of time before the flight of realistically massed pterosaurs was considered in the technical literature (well, beyond saying they couldn’t fly). We were kicked into action, though, when press reports of an abstract presented by Katsufumi Sato et al. were released in April 2009, saying giant pterosaurs couldn’t fly. Keen members of the palaeoblogsphere may remember this ruffled a fair few feathers when it was released, and their paper (Sato et al. 2009) followed shortly to similarly raised-eyebrows. Most folks even vaguely familiar with large pterosaurs were astonished to see them cap flight at such a low size: 41 kg and 5 m wingspans are very middling in the spectrum of pterosaur size (10.5 m spans and 250 kg body masses are considered maximum in our paper). Because plenty of clearly-flight adapted forms got much larger than this, I got to work on a response. Mike and I have fairly regular correspondence and were talking about the project soon after I started, and it wasn’t long before we realised that working together would make the project much stronger.

Plus, I had giant pterosaurs on the brain at that time. I’d just started work on a massive modelling project where I had to build several models of the largest pterosaurs going. The logistics and costs of building a 13 m span pterosaur against a 10 m span animal is quite something, so I figured a little checking of the wingspans of these poorly known animals wasn’t the worst way to spend an afternoon as it would avoid having to find a bigger workshop. The timing of this was spot on for the project with Mike, too, as it meant we could ensure the size estimates for our flight analysis were as accurate as we could make them. These two events combined to form the beginnings of the paper and reminds me that we started it well over a year ago: where did that time go?

What was the most surprising finding to you, and why?
The most surprising? Hard to put my finger on one thing exactly: we covered quite a lot of topics, and each had their own intriguing little revelations. I mean, the 13 m span estimates of Arambourgiania, the giant pterosaur from Jordan, always seemed a little iffy to me because they were based on a single neck vertebra, but not Hatzegopteryx. Being based on forearm material, I figured the 12 m span estimate for this critter was a sound bet but, no, the material just seems distorted to appear bigger than it actually is. The numbers generated in the flight analysis for the speed of flying giant pterosaurs were impressive, too. The thought of a giraffe-sized pterosaur pumping its wings to scream overhead at 75 mph is staggering: this is real ‘if I had a time machine…’ stuff.

That said, for all these little surprises, the biggest ones came from the paper’s release and press coverage: I was really blown away to see just how much interest we had. To be honest, we did want to make a splash because, following the Sato et al. abstract, the internet is awash with articles saying giant pterosaurs couldn’t fly. We wanted to balance it out a little (this is also, incidentally, why we chose PLoS ONE as our venue: we want interested people of all backgrounds to be able to see our rationale for flighted giants: open access is definitely the way forward, folks). However, I was truly taken aback when our work was quoted directly alongside some half-naked chick in the British tabloids newspaper, The Sun. How often do science stories penetrate that far into the press, let alone those dealing with relatively unimportant extinct flying reptiles? I can only assume that pterosaurs are becoming more exciting and cool with every new discovery, or it was a slow news day. Either way, I’ve not stopped telling people about that since.

Next Time. . .the ins and outs of trans-Atlantic collaborations, and what the media should have mentioned.

Citations
Sato, K., Sakamoto, K., Watanuki, Y., Takahashi, A., Katsumata, N., Bost, C., & Weimerskirch, H. 2009. Scaling of soaring seabirds and implications for flight abilities of giant pterosaurs. PLoS ONE, 4 (4), DOI: 10.1371/journal.pone.0005400.
Witton, M., & Habib, M. (2010). On the size and flight diversity of giant pterosaurs, the use of birds as pterosaur analogues and comments on pterosaur flightlessness PLoS ONE, 5 (11) DOI: 10.1371/journal.pone.0013982

Ancient Beavers in PLoS ONE: Interview with Josh Samuels

An earlier post here detailed a study just published in PLoS ONE, which focused on unraveling the relationship of an extinct Chinese beaver, Sinocastor, to its modern cousins in the genus Castor. Using a combination of morphometrics (shape analysis) and good old fashioned description, a team led by paleontologist Natalia Rybczinski concluded that Sinocastor is indeed quite distinct from today's Castor.

Yesterday I caught up with one of the co-authors of the study, Josh Samuels. Josh is an expert on fossil rodents (especially beavers) and morphometrics, working as a paleontologist at John Day Fossil Beds National Monument. He was kind enough to answer a few questions about his part in the project.

You have quite a track record of working with beavers and other rodents. How did you get interested in this group in the first place?
Ever since I was a kid, I have been interested in understanding how extinct species lived. In college I became interested in studying the evolution of mammals, particularly their dietary and locomotor specializations. I learned that rodents are the most species rich group of mammals and have amazingly diverse ecologies, with everything from semi-aquatic carnivores to gliding herbivores and blind burrowers. Despite their diversity, the evolution of rodents has not been as well studied as some other groups. Beavers, in particular, are known for their dramatic impact on ecosystems and have an excellent fossil record. Given their importance today, I find working to understand their evolution to be quite fascinating.

The PLoS ONE paper certainly was a collaborative effort - what role did you play in the research?
Some of my past research used geometric morphometrics to examine how skull shape in rodents relates to their ecology. Natalia approached me about the possibility of using similar techniques to examine how Sinocastor was related to living and extinct beavers. I helped design the methods and ran most of the analyses, and writing the paper was definitely a group effort. Having a group of collaborators with different skills really helped the project come together smoothly.

Was there anything particularly surprising to you about the results?
Given the broad geographic range of Eurasian and North American beavers today, I was surprised to find subtle, yet consistent differences in shape among species. One of the specimens in our analysis was from a peat bog in England, but its skull shape was almost identical to individuals from China and Russia. This really gives me hope that these techniques could be used an effective way to look at the phylogenetic relationships of extinct species.

Thanks, Josh!

Citation
Rybczynski, N., Ross, E., Samuels, J., & Korth, W. (2010). Re-evaluation of Sinocastor (Rodentia: Castoridae) with implications on the origin of modern beavers. PLoS ONE, 5 (11) DOI: 10.1371/journal.pone.0013990

Full disclosure: I am an editor at PLoS ONE
Image credits: National Park Service website

Re-Evaluating Ancient Beavers

Beavers are some of the most distinctive (and largest) rodents around today. Two species of the extant beaver, Castor, are found throughout the northern hemisphere, and these animals have an enormous effect on their landscapes. Beavers are perhaps most famous for their dam-building activities, altering the flow of streams and generating valuable wetlands used by other animals. Surely, the impact of this group extends far back in geological time.

Many early beavers were fossorial, or burrowing, with little indication of aquatic tendencies. For instance, the 25 million year old Palaeocastor produced giant spiraled burrows known as "devil's corkscrews." Perhaps the acme of beaver evolution occurred during the Miocene (~23 to 5 million years ago). At least 12 genera lived worldwide; only one of these, Castor, survived to the present day. An obvious question for paleontologists thus concerns the when and where of modern beavers' origins.

Enter Sinocastor. This genus was named in 1934 by famed Chinese paleontologist C.C. Young, for several species recovered in China and Mongolia from rocks deposited during the last 5 or 6 million years. Almost immediately, other authors lumped Sinocastor into Castor, and there Sinocastor has stayed for the most part. Was this a valid opinion, or did such lumping obscure a more interesting paleontological pattern?

Fortunately, the exquisitely-preserved type (first described) specimen for Sinocastor anderssoni was recently restudied by a team of paleontologists from Canada and the United States. Led by Natalia Rybczynski of the Canadian Museum of Nature, the paper describing their findings appeared this week in the open access journal PLoS ONE.

The authors of the new paper used geometric morphometrics, a type of shape analysis, to see just how similar the skull of Sinocastor (at right) was to modern and recently extinct Castor. For additional comparison, the early European beaver Steneofiber castorinus was also thrown into the mix. Points on the various skulls were digitized from photographs and run through computer programs that calculated the similarity between the specimens.

In the end, the skull of Sinocastor fell well outside the anatomical range for modern and even most extinct beavers. Rather substantial shape differences distinguish Sinocastor from Castor; for instance, the snout is shorter and the braincase broader in Sinocastor. Although genera are always somewhat subjective, Rybczynski and colleagues argue that the major differences between Sinocastor and the species of Castor warrants the retention of Sinocastor as its own genus.

Based on several other lines of evidence (including tooth anatomy), it is suggested that Sinocastor may be the sister taxon (closest relative) to modern beavers. In concert with dated fossils, this means that the common ancestor of these two kinds of beaver may have originated in eastern Asia and then spread westward into Europe and eastward into North America. The arrival of modern beavers on that landscape must have had massive ecological consequences - only more investigation of the fossil record will tell!

Stayed tuned: Tomorrow, an interview with Josh Samuels, one of the paper's authors!

Citation
Rybczynski, N., Ross, E., Samuels, J., & Korth, W. (2010). Re-evaluation of Sinocastor (Rodentia: Castoridae) with implications on the origin of modern beavers PLoS ONE, 5 (11) DOI: 10.1371/journal.pone.0013990

Full disclosure: I am an academic editor at PLoS ONE, the journal at which the paper described here was published.
Image credits: Image at top from Wikimedia Commons (by Steve); fossil skull modified from Figure 14 in Rybczynski et al., 2010.