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.