Serendipaceratops arthurcclarkei, an Australian Mystery

Serendipaceratops arthurcclarkei is one of the mysteries of dinosaur-kind, lurking Gollum-like in the shadows, threatening to overturn everything we know about the ceratopsians, sowing doubt and confusion. Well, maybe not everything, but possibly their origins and certainly their geographical distribution. In March of 2004, National Geographic News posted a story about the Dinosaurs of Darkness traveling exhibition curated by Monash University paleontologist Patricia Vickers-Rich, and the story briefly mentions the strange new dinosaur from Australia:

Other dinosaurs from southern Australia include Serendipaceratops arthurcclarkei, one of the oldest horned, or frilled, dinosaurs known, which suggests that horned dinosaurs may have originated in the southern polar region.

"That group is most well known from Mongolia, where Protoceratops occurs in the very late Mesozoic/late Cretaceous. The material of Australian origin is early Cretaceous," Vickers-Rich said.

Nat Geo's reporter, John Roach, may have misunderstood Vickers-Rich; her quote doesn't claim that horned dinosaurs originated in Australia (and I've been unable to find any quotes from her that do), but refers specifically to those ceratopsians to which Serendipaceratops is most closely related. It's still a puzzling story.


Leptoceratops by Peter Trusler, via Wikimedia Commons.

Known only from a single ulna - and possibly another pulled from the nearby Dinosaur Cove fossil locale - Serendipaceratops is a huge question mark. Initially skeptical, Vickers-Rich and her partner-in-paleontology, Thomas Rich, decided that the ulna belonged to a ceratopsian based on its strong resemblance to the corresponding bone of Leptoceratops, a well-known Late Cretaceous dinosaur from North America. Lepto is closely related to the more famous Protoceratops, also known only from the Late Cretaceous. Therein lies the problem: if you accept the protoceratopsian nature of Serendipaceratops, it lived tens of millions of years before anything that resembled it. What the heck is it doing in Australia?

It may not seem like a big deal, but consider the following:

• Yinlong, the earliest confirmed ceratopsian, hails from Jurassic China.
• Every other ceratopsian known to paleontologists comes from Asia, Europe, or North America.
• The vast majority of protoceratopsians come from China and Mongolia.

At the time of Yinlong, the continents we know today were still mashed together into the supercontinent Pangaea (click for map). Pangaea was a great C-shaped landmass, with the areas we know as Australia and China at opposite ends. It's possible that ceratopsians might have ranged between Australia and China; it simply would have required populations to travel between those terminal points of the "C" via Africa or South America, and possibly India. You would expect to find something similar to either protoceratopsids or primitive ceratopsians somewhere in these places. To date, none have been found (save for one dubious jawbone from South America that has been lost), but there also aren't many rich, temporally relevant dinosaur-bearing deposits in those regions.

In the recent description of Sinoceratops, the only non-North American ceratopsid, Xu Xing wrote that the apparent endemism of ceratopsids to North America probably reflects gaps in the fossil record rather than actual limitations on the family's Cretaceous range. The mystery of Serendipaceratops is complicated by much larger gaps. And at least Sinoceratops has the decency to have been contemporary with its ceratopsid kin.

It seems simpler to me that the ulna's resemblance to that of Leptoceratops is a coincidence. That's where my money would be, if gambling on paleontology was a sane thing to engage in. Hopefully, the notoriously stingy Australian strata will give up more related material. At the very least, if Serendipaceratops is not a ceratopsian, it's a totally unique Australian dinosaur. That's a pretty good resolution, and still a worthy tribute to the man it was named for.

Ceratopsian Wrangling

Here's a roundup of links relating to some of the new ceratopsians we've been delighting in recently. Of course, many of the new taxa introduced in the last couple of weeks come from the long-awaited new book New Perspectives on Horned Dinosaurs: the Royal Tyrrell Museum Ceratopsian Symposium. The symposium was held in the autumn of 2007, and brought together a couple hundred experts in the field to share recent research.

Michael J. Ryan talks Medusaceratops lokii
The Vancouver Sun has an article about Medusaceratops featuring New Perspectives on Horned Dinosaurs lead editor, paleontologist Michael J. Ryan. Regarding the name he gave the new ceratopsian, he tells the paper, "One of the things I have a problem with as a paleontologist is how some of my colleagues come up with terribly unpronounceable names... I like to give my dinosaurs names that roll off the tongue and actually evoke an image." Hear, hear.

Jim Kirkland writes about Diabloceratops eatoni
In a guest post at Dave Hone's Archosaur Musings, paleontologist Jim Kirkland sums up what's cool about the new, also-wonderfully-named Diabloceratops. There are some fine photos of the skull, which is a thing of beauty.

Four foot horns from Mexico

Reconstruction by Lukas Panzarin

Coahuilaceratops magnacuerna is the new ceratopsian from Mexico, making news because of its enormous horns. I'd expect a story about it from Nat Geo soonish, as they partially funded the Utah Museum of Natural History dig.

Ojoceratops fowleri
The Bisti-De-Na-Zin Wilderness of New Mexico recently produced the tyrannosaur Bistahieversor, and now gives us Ojoceratops, a mid-size ceratopsian. Discovered by a team led by Robert M. Sullivan of State College of Pennsylvania, Ojoceratops gets its name from the Ojo Alamo Formation in which its bones were found. It's a controversial rock formation, as it is right at the boundary of the Cretaceous and the Paleocene, the first age of the post-dinosaur world. Paleontologist Jim Fassett has argued for years that dinosaurs may have survived a while after the Chicxulub impact based on fossils found in this layer. Sullivan has argued against this, so I doubt that any such assertions will be in the description. There's a great summary of the Ojo Alamo controversy at Laelaps; articles on Ojoceratops at the Santa Fe New Mexican and Pennlive.com.

These are the few that have received coverage; there are more that haven't had much written about them, including Rubeosaurus, Utahceratops*, and Tatankaceratops. I wrote a bit on Ajkaceratops and a bit more on Sinoceratops. A good place to keep up with recent discoveries, including plenty I haven't had the time to write about, is Dinosaur Central.

Finally, if you're a Facebooker, Ceratopsians have their own fan group, moderated by the Royal Tyrrell's Darren Tanke. More exciting than the Beyonce group, for sure.

*Kind reader 220mya has informed me that Utahceratops is not included in this title, and not yet described.

Yinlong and the Roots of the Ceratopsian Family Tree

In December, I wrote about one of the coolest toy lines I've seen in a long time: Evolvems, plush animals that reveal one of their evolutionary descendants when turned inside out. The Evolvem I posted was the lone dinosaur pair in the line: Yinlong-Styracosaurus. Styracosaurus is one of the most popular ceratopsids, appearing in children's books and toy lines for years because of its handsome, spike-studded frill. Yinlong, however, is pretty obscure.

It's easy to understand why. It's a recently discovered dinosaur, its Chinese name (meaning "hidden dragon") doesn't immediately suggest "dinosaur" to English-attuned ears, and it's not exactly a giant. To most people, it probably seems pretty humble.


Yinlong downsi by Andrey Atuchin, via the Natural History Museum, London

But the Evolvems brain trust picked Styracosaurus' partner-in-plush for a good reason. Discovered in China in Jurassic rock, Yinlong downsi is the oldest ceratopsian yet discovered. It lived alongside Guanlong wucai, an early relative of T. rex. If you were going to give T. rex and Triceratops the "Muppet Babies" treatment, you could set it in Late Jurassic China.

This spells out a likely Asian origin for the ceratopsians. Sinoceratops, the new Chinese ceratopsid, opens the possibility that these more derived members of the group may also have their origin in China, rather than arising in North America after more primitive ceratopsians found their way there via the Asian-Alaskan land bridge formed in the Cretaceous. It's also plausible, to me at least, that Sinoceratops or its recent ancestors wandered back to Asia from North America. Perhaps something about its biology - more generalized, mixing traits of the centrosaurines and chasmosaurines - made it better suited for its Chinese habitat, thus making this hypothetical migration - probably occurring over many generations - a reasonable pursuit. Bear in mind, I haven't read anyone put this forward, so it's just my idle speculation. Hopefully some earlier Cretaceous strata will cough up some ceratopsids of their own.

Sinoceratops and the Ceratopsian Family Tree

I think I'll keep the ceratopsian train chugging along here. First, a correction. Yesterday I mentioned that the Sinoceratops description in the Chinese Science Bulletin puts forth the idea that the ceratops-ians may have originated in Asia. Actually, Xu Xing and his coauthors write this of the ceratops-ids. Those couple letters make a big difference. My lovely brain has a nasty habit of fudging subtle details like those suffixes. Maybe laying out the context into which these new dinosaurs fit will be a sort of mental strength training.

When I began writing today, I figured I'd talk about Yinlong, an important basal ceratopsian from China. But I think it may be better to draw the big picture, the ceratopsian family tree, if you will, and save Yinlong for tomorrow. This will dip into the often maddening world of taxonomy, the classification of living things, which is an even more difficult undertaking when dealing with a source of data as fragmentary as the fossil record. While I'm not looking to get granular, I'll preface this by saying that names of groups and the members therein may change as paleontologists find new fossils and debate how the old ones relate to each other.

The ceratopsians are a member of the largely herbivorous clan of dinosaurs called the ornithischians, which I discussed a bit in a post from last August. Most of the ceratopsians, save for some of the most primitive, are quadrupedal, and the group ranges widely in size, from as big as a dog to larger than an elephant.


The pelvic differences between saurischians and ornithischians. By yours truly, a derivative work based on separate diagrams by wikimedia user Frederik.

The ceratopsians all share a completely unique bone called the rostrum, which forms the top half of their beaks. Find one of these, and you've got a ceratopsian for sure.

There are many families under the ceratopsian umbrella, but I'm not going to get into the details of all of them. As this review is spurred by the Sinoceratops discovery, I'll instead discuss its family, the ceratopsids: the largest ceratopsians, distinguished from each other by a variety of ornaments on their skull. The basics are the bony frill extending from the back of their heads and the horns, bumps, and knobs on their faces - working from these basic elements, the variety is astounding.

Based on these ornaments, the ceratopsids are then divided into two main posses: the centrosaurinae, which generally bear larger nose horns with smaller frills and brow horns, and the chasmosaurinae, which have the opposite arrangement. Looking at those horns is a good way to get a rough idea of what kind of ceratopsid you're dealing with - just as you might look at the shape of a beak to begin to identify a strange bird in your yard. Some prominent chasmosaurines are Triceratops, Chasmosaurus, and the new Medusaceratops; the centrosaurines include Styracosaurus, Einosaurus, and Centrosaurus. Sinoceratops is notable for the blend of centrosaurine and chasmosaurine characteristics in its skull, which is the basis for Xing's idea of an Asian origin for the ceratopsids.


Centrosaurines, by Nobu Tamura, via Wikimedia Commons

It used to be a given that if a new ceratopsid was discovered, it would be from western North America in Cretaceous rock. Sinoceratops naturally flips the geographical part of that on its head, and raises questions about how wide the range of this classically North American group could have been. Xing floats two guesses as to why ceratopsids are mostly found in North America. First, there may have been factors that limited the ceratopsids geographically, and what we see is what we get. This is certainly plausible, but a bit shaky considering how few windows to the Cretaceous the rocks give us. He favors the second option, which is that we simply haven't found everything. Sinoceratops is a tantalizing look at what may be there waiting to be unearthed.

Hellraising Hornheads

You may have noticed a ridiculous number of news stories about ceratopsians - the beaked, frilled, frequently horn-sporting relatives of Triceratops - in the last week or so. Or maybe you don't have a Google Alert set up for "dinosaurs," in which case I should advise you to set one up ASAP. You'll be delighted by how much it raises your esteem with your peers.

Sober social advice aside, the hornheads have been popping up all over the place, due in part to the release of New Perspectives on Horned Dinosaurs from Indiana University Press. The book includes descriptions of a number of new species, including Diabloceratops eatoni, Medusaceratops lokii, and Coahuilaceratops magnacuerna. Coahuilaceratops is making waves for its enormous brow horns and for being Mexico's first ceratopsid, which is the largest, most lavishly ornamented group of horned dinosaurs.

Not to be outdone, China now has one of its own as well; it's named Sinoceratops zhuchengensis and is described in a new paper in the Chinese Science Bulletin. Both of these national firsts extend the group's known western North American range. Smaller, primitive ceratopsians like Psittacosaurus and Protoceratops are well-known from Asia, so the Sinoceratops discovery is especially significant. The authors of the study present their own revision of the ceratopsid family tree and state that the ceratopsians may have originally arisen in Asia, flourishing generations later in North America. The recently introduced Ajkaceratops - which was a member of the broader ceratopsian family - would seem to support this idea, as its ancestors were likely also of Asian descent.

If you want to impress people by picking a favorite dinosaur that's a little left-field, cool-looking and cool-sounding, you've got some solid options here. Personally, I'm going with Medusaceratops - check out the amazing Luis Rey reconstruction here.

Also cool is that the cover model for New Perspectives on Horned Dinosaurs is none other than LITC's patron dinosaur, Chasmosaurus. Cleveland Museum of Natural History paleontologist Michael Ryan, lead editor of the book, identifies the artist as the Royal Tyrell Museum's Donna Sloan.