It's been a week since I last wrote about Serendipaceratops, a glaring problem I'll now correct. A refresher: Serendipaceratops arthurcclarkei is a dinosaur named by Australian paleontologists Mark Rich and Patricia Vickers-Rich based on a single ulna. After seeing a Leptoceratops ulna shown to them by Canadian paleontologist Dale Russell, they decided it represented a neoceratopsian - living tens of millions of years before the other neoceratopsians and really far away from the family's predominant territory of Asia.
As luck would have it, on May 22, 2010, Argentinian Museum of Natural Sciences paleontologists Federico L. Agnolin, Martin D. Ezcurra and Diego F. Pais, joined by Steven W. Salisbury of the University of Queensland, published a sweeping reappraisal of the Mesozoic fauna of Australia and New Zealand. Huge thanks to commenter Jay, who tipped me off to this. I have been able to get a copy of the paper and took a look at it. It's been the subject of debate surrounding nomina dubia, "dubious names." Basically, it works like this: Paleontologist A describes a fossil and decides that it's unique and thus warrants the naming of a new species. Then, paleontologists B through K look at the specimen and decide that the fossil isn't actually that unique, or more associated fossils are needed to make the determination. Paleontologist A's name for the fossil is then considered a nomen dubium. Mickey Mortimer's Theropod Database Blog and Jamie Headdon's The Bite Stuff each have posts discussing their respective opinions on the topic.
As Jay said in his comment, Agnolin et al suggest that Serendipaceratops is probably not a ceratopsian, and cannot be confidently assigned beyond being an indeterminate Genasaurian. The clade Genasauria is a large group that includes the ceratopsians, the ornithopods (Iguanodon, the duck-bills, and their kin), the stegosaurs, and armored dinosaurs like Ankylosaurus and Edmontonia. Almost all ornithischian dinosaurs, except for a handful of the most primitive ones, fall under its umbrella.
The Australian ankylosaur Minmi, by Mariana Ruiz, via Wikimedia Commons.
The authors argue that Serendipaceratops simply doesn't have adequate fossil evidence to draw any strong conclusions as to what kind of critter it was, though they do note that "...the proportions of the ulna of Serendipaceratops are closer to Minmi sp. and other ankylosaurians than to any neoceratopsian." Thus, they decide that Serendipaceratops arthurcclarkei is a nomen dubium.
In the chance that Agnolin and his crew's ideas are borne out, it may be a good idea to horde some Serendipaceratops keychains.