The Open Museum Notebook - Torosaurus Style

A new paper on the Torosaurus / Triceratops issue was just published in PLoS ONE, bringing some additional analysis to the table. I won't comment on it any more here (I'm saving my thoughts for a formal reply on the PLoS ONE website itself), other than to refer you to my own paper and the Scannella & Horner response.

In any case, I have a pile of notes from my own work on Torosaurus (or whatever we should call it), and figured it was time I distribute them a little more widely. So, I just uploaded my notes on the Yale Torosaurus specimens to figshare.com. There isn't really anything earthshaking in there (most of the meat of it has been previously published), but in any case now other folks can use them. The sketches of real bone vs. reconstruction should be particularly useful.

My sincere hope is that at least a few other paleontologists will follow suit with their own notebooks - there are a lot of unused data that will never see the light of day otherwise. I also have a goal of gradually digitizing and posting my other museum notebooks, but that will probably take some time!

Citation and Link

Notes and Observations on Specimens of Torosaurus at the Yale Peabody Museum of Natural History. Andrew Farke. Figshare. Retrieved 15:40, March 02, 2012 hdl.handle.net/10779/664bf2cb5ac486da32c7fb7261e595cd

Update: Since this posted, I have uploaded a number of other notebooks. Find them on my figshare author page.

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.

Triceratops Combat?

Exactly how did Triceratops and other horned dinosaurs use their cranial weaponry? Today, my co-authors Ewan Wolff, Darren Tanke, and I published new research in the online, open access journal PLoS ONE, giving our take on the issue. In a study spanning four years and over a dozen museums, we have marshalled what we think is the best evidence to date that Triceratops may have locked horns with their own kind.

Restoration of Triceratops in horn-to-horn combat. Image copyright Lukas Panzarin, courtesy Raymond M. Alf Museum of Paleontology.

The Background
The ceratopsids, or horned dinosaurs, present a bewildering array of cranial headgear. Triceratops was one of the earliest discovered and best known, with its distinctive dual brow horns, single nose horn, and a solid frill of bone over the neck. Subsequent discoveries revealed a clade chock full of anatomical diversity - single horns, triple horns, and frills sporting all sorts of odd accessories. Consequently, a whole host of functional explanations have been dreamed up for these bones.

Defense against predators was an early, popular explanation. With threats such as Tyrannosaurus stalking the Cretaceous landscape, Triceratops and relatives surely would have used their horns for defense if they had to. Yet, this is not the primary function of the horns in modern animals. More commonly, horns, antlers, and other appendages are used for intraspecific combat and display--not against predators. A good example is the massive horns of the bighorn sheep. Careful behavioral studies have shown them to be employed in impressive visual display to other sheep, or for combat over territory, mating rights, dominance, etc. These modern analogs were quickly compared with ceratopsids.

In addition to the determination of function by analogy, some paleontologists noted odd markings on the skulls of some horned dinosaurs. Perhaps a chunk of the frill was missing, with evidence of healing. Maybe there was an abnormal, oddly positioned hole on the skull. Inevitably, these oddities were attributed to "horn gouge wounds." These alleged pathologies were interesting--but anecdotal. Without a broader context, any attempts to infer a cause for the "injuries" usually amounted to constructing a "Just So Story."

Recently, the tide has turned against the idea of horns-as-weapons in Triceratops and its relatives. Research by Kevin Padian, Jack Horner, Mark Goodwin, and others have suggested that the odd cranial ornamentation of many dinosaurs was for more peaceful purposes--specifically, species recognition (picking out members of their own kind amongst a sea of similar species). Although this idea certainly has its merits, I was never quite convinced that the horns of Triceratops were completely benign (and to be fair, I don't know that the species recognition proponents were suggesting this as the only function, either). At the same time, I wasn't exactly convinced that every single ding on a fossil skull should be considered evidence for combat.

What We Did
I've been really interested in the issue of horned combat in Triceratops for some time. Several years ago, I published a brief study, using plastic models, that demonstrated such combat was at least physically possible. I made some predictions about where we should expect injuries on the skull, noted similarities with published anecdotes of alleged injuries, and left the issue open for a follow-up study. The models were fun to play with, but I wanted to know if this combat actually happened in real life! And, I knew that paleopathology--the study of disease and injury in fossils animals--was probably the best approach. Unfortunately, I didn't know that much about the topic.

So, I teamed up with two experts. Darren Tanke works at the Royal Tyrrell Museum of Paleontology, and is an expert in both paleopathology and ceratopsian dinosaurs. Ewan Wolff recently finished his dissertation on oral pathology in archosaurs at Montana State University, and now is a student at the University of Wisconsin-Madison School of Veterinary Medicine. Ewan and Darren provided expertise in identifying and interpreting the markings we observed on the ceratopsid skulls.

Our logic was simple--if ceratopsid dinosaurs used their horns against each other in combat, evidence of this should be found in bony lesions on the skull. And, assuming that animals with different horn configurations fight differently (a fair assumption from observations of modern horned critters), we should find differing rates and patterns of lesions between different species of horned dinosaurs. If the horns were not used in combat (or specifically, patterns of horn locking that could result in injury to the skull), we should see no difference between various species.

So, we surveyed many, many specimens at over a dozen museums across North America. We looked for any evidence of pathology, and recorded its location on the skull. Two genera were the focus of our research--Triceratops (pictured at the top of the post) and Centrosaurus (pictured below this paragraph). Centrosaurus has only a single nasal horn (and no massive brow horns), so we assumed that it would be most likely to show differences from Triceratops if there were any to be found. After years of data collection, we subjected all of the numbers to statistical analysis. Lots of folks (Darren and I included) had described anecodotal reports of pathology before--but nobody had subjected them to the rigors of statistics.

One artist's concept (courtesy Wikimedia Commons) of Centrosaurus in combat.

What We Found
Briefly, we found that most bones of the skull that we examined did not show statistically significant differences (i.e., P>0.05) in rate of pathology between the two genera. Except, that is, for the squamosal bone of the frill (shown on the figure below). But what does this mean?

Schematic showing rates of pathology (number of pathological elements/total elements examined) for Triceratops (top) and Centrosaurus (bottom). The squamosal rates, highlighted here, were different from each other at P<0.05.

Did Triceratops Fight Each Other?
As you can probably guess by now, we postulate that the differences in rates of pathology between Triceratops and Centrosaurus were caused by behavioral differences. In other words, because Triceratops were locking horns with either other, they got injured. However Centrosaurus used its horns (whether for combat or display, or whatever), they didn't commonly cause injury to the squamosal bone. We do consider some alternative explanations for the lesions (predator attack, microbial origin, etc.), but generally discount these (read the paper for a full explanation).

As a reminder, if the horns were only being used for display (species recognition, or whatever), we wouldn't expect to have seen these differences in pathology rates between the two species. Thus, I am reasonably comfortable saying that the horns weren't "just for looks."

What Does This Mean for Dinosaur Research?
The statistical study presented here is some of the best evidence to date (in our opinion) for intraspecific combat in Triceratops. Centrosaurus may well have done the same, just in a very different manner (flank butting, or something like that). Or, maybe Centrosaurus was a more peaceful taxon--we just don't know yet. Lots more research is needed in this area.

Another big question is why these animals were fighting. Mating rights? Sexual dimorphism hasn't been demonstrated in the taxon, so it doesn't seem like males and females are set up any differently in terms of horn configuration (but further study may change this). Territory? Who knows (and good luck investigating this with fossils!). General bad temper? Your guess is as good as mine. We may never know the why in this case.

Centrosaurus came from an ancestor with big old brow horns--perhaps this ancestor lost the horns in favor of a kinder, gentler approach. The latest centrosaurines (living millions of years after Centrosaurus), such as Pachyrhinosaurus, ditched their horns altogether in favor of big bony pads on the skull. So, did centrosaurines evolve towards less risky forms of combat? Again, this is another hypothesis that should be tested more thoroughly. There's lots more work to do!

On a more methodological note, we hope that more studies of dinosaurian paleopathology will adopt a statistical approach. Anecdotes are interesting, and can be very informative in some cases, but they only tell part of the story. There is strength in numbers!

What Aren't We Saying?
Because cranial function is a contentious issue, I just want to make clear on what we aren't claiming. (I am speaking for myself here--my co-authors are probably largely in agreement)

• All injuries on ceratopsid skulls are attributable to combat. No, no, no. Just because there is a ding on the skull doesn't mean it's a combat wound. Almost certainly, some non-combat injuries are included in our sample--this is why we looked at overall patterns, rather than anecdotal cases. I would be willing to say, though, that the overall pattern of lesions (at least on the squamosal) suggests that most of them were caused by the horns of other ceratopids.
• Ceratopsid horns were only for combat. Again, no. This isn't the case in modern animals, and it likely wasn't the case for ceratopsids. As I (and Darren) have said elsewhere, ceratopsid horns were probably like Swiss Army Knives--multi-purpose tools. Fighting, defending, showing off, cooling off, you name it. I am just saying that now we shouldn't exclude fighting as a function.
• All ceratopsids used their horns identically. No. Different horn morphologies suggest different uses--and I would be willing to believe (as others have suggested) that animals such as Pachyrhinosaurus focused on flank-butting behavior (rather than head-to-head combat). Again, this will need more work.
  

Parting Thoughts
This has been a really, really fun study, and one that I hope will spur more research on the possibilities for skull function in horned dinosaurs. We haven't heard the last on this issue, rest assured. There are lots more specimens, new species to describe and discover, and many other people working to better understand these magnificant animals. I would also like to publicly thank my co-authors--I have learned so much about paleopathology and ceratopsids from you! Finally, a big thank you to our artist, Lukas Panzarin, who skillfully brought to life a long-vanished Triceratops battle.

Farke AA, Wolff EDS, Tanke DH (2009). Evidence of Combat in Triceratops. PLoS ONE, 4 (1):e4252. DOI: 10.1371/journal.pone.0004252
Read and download it for free at: http://dx.plos.org/10.1371/journal.pone.0004252

Coming soon. . .other goodies related to this paper, including the open source software used in the research, the open access publishing experience, and much more!