Horned Dinosaurs: When It Rains, It Pours

2010 will surely go down as the annus mirabilis of horned dinosaur research. Between the publications of the horned dinosaur symposium volume (with its myriad new taxa and other exciting pieces of research), a "bagaceratopsid" in Europe, a true ceratopsid in Asia, the hypothesis that Torosaurus and Triceratops are growth stages of the same taxon, and more, it's really tough for a "ceratophile" (to borrow Peter Dodson's term) to keep up!

Today continues the embarrassment of ceratopsian riches. With my co-authors Scott Sampson, Mark Loewen, Cathy Forster, Eric Roberts, Alan Titus, and Josh Smith, I'm pleased to introduce you to Utahceratops gettyi and Kosmoceratops richardsoni (at top and bottom, respectively, in the image at right), freshly published in PLoS ONE. Although it's been a long time coming, our hope is that these new critters will really knock your socks off!

So what's so special about these two animals? Well, for one they're new dinosaurs. And new horned dinosaurs at that. On a broader note, our new critters (along with careful radiometric dating of the Kaiparowits Formation, the rock unit in southern Utah from which they originated) provide important evidence for dinosaur provincialism during the Late Cretaceous. In other words, these big, elephant-sized dinosaurs weren't traveling far. They're the same age as dinosaurs known from much further to the north, yet represent a very different part of the horned dinosaur family tree. This is strange, especially when you consider that today there is only one (or maybe two, depending on whom you ask) elephant species in all of Africa! 75 million years ago, there were three or four closely related species of horned dinosaur living simultaneously on that little strip of beachfront property that comprised western North America. And that's not counting a few more less closely-related horned dinosaurs (centrosaurines) that lived at the same time! Truly weird.

There's been a lot said more eloquently elsewhere about these animals, so I'm just going to close with an answer to the question that should be at the top of many people's minds. Given the possibility that Torosaurus and Triceratops might be growth stages of a single species, how do we know that Utahceratops and Kosmoceratops aren't just growth stages of one species? After all, they lived at the same time in the same place, and end up somewhat close together on the phylogenetic analysis. Well, we certainly haven't done much in the way of histology yet, which would lay the issue completely to rest. However, as readers of the paper will note, we have obvious juveniles (based on sutural fusion and cranial element size) of both species. Although these remain to be published, in my opinion they pretty firmly demonstrate that both species of dinosaur were very different very early on in their development.

So, go read the paper!

Full disclosure: I am a section editor at PLoS ONE, the journal at which this new paper was published. However, I had absolutely no involvement in the handling of the manuscript (assigning the academic editor, selecting reviewers, making a publication decision, etc.).

Image credit: Lukas Panzarin

Citation
Sampson, S., Loewen, M., Farke, A., Roberts, E., Forster, C., Smith, J., & Titus, A. (2010). New horned dinosaurs from Utah provide evidence for intracontinental dinosaur endemism PLoS ONE, 5 (9) DOI: 10.1371/journal.pone.0012292