A Giant From New Mexico: Titanoceratops

Many unknown dinosaurs await discovery in rock formations all over the world, but some new species are hiding in plain sight. One such animal, described in an in-press Cretaceous Research paper, had one of the largest heads of any dinosaur.

As recounted in the study by Yale paleontologist Nicholas Longrich, in 1941 the partial skeleton of a large horned dinosaur was found in the 74-million-year-old rock of New Mexico's San Juan County. The bones stayed in their field jackets for over five decades, and it was not until 1995 that they were prepared. Using the dinosaur Pentaceratops as a model—which is common in the New Mexico rock in which the skeleton was found—the giant dinosaur was completed and put on display at the Sam Noble Oklahoma Museum of Natural History, where it gained the Guinness World Record for the largest dinosaur skull ever found (a somewhat dubious distinction since the skull was incomplete and most of the frill was reconstructed with plaster).

But the Sam Noble specimen may not be a Pentaceratops at all. Longrich lists 22 features that distinguish the large specimen from the smaller Pentaceratops and more closely associate it with the subgroup of horned dinosaurs containing Triceratops, Torosaurus and their closest relatives (called the Triceratopsini). On this basis Longrich has called the unique specimen Titanoceratops.

The recognition of Titanoceratops generates new hypotheses about the evolution of the last of North America's horned dinosaurs. At about 74 million years old, Titanoceratops extends the range of the Triceratopsini back about five million years and may indicate that large body size evolved among this subgroup earlier than had been thought. Though certainly an impressive specimen, the main value of Titanoceratops may be in helping paleontologists trace the evolution of horned dinosaurs just before the catastrophic end-Cretaceous mass extinction.

Dinosaurs do not come with name tags, however, and as this study shows, specimens are subject to reassignment. Specimens thought to belong to one species have turned out to represent another, and dinosaurs thought to be unique have been found to be growth stages of an already known species. During the past year paleontologists have been actively debating whether or not the horned dinosaur Torosaurus is actually the adult stage of Triceratops, and e-mails sent through the Dinosaur Mailing List have already suggested that Pentaceratops and Titanoceratops may be growth stages of just one species as well. This is not something that will be resolved in a week, a month, or even a decade. Skeletal anatomy, the microstructure of dinosaur bone and the geological context of multiple specimens all come into play, and (as always) more fossils are needed for comparison. The animal Longrich has named Titanoceratops certainly did exist, but as with any other species, the animal's name is a scientific hypothesis that will likely be discussed and debated in years to come.

There was also an academic substory to the debut to Titanoceratops. The paper describing the dinosaur became available as an accepted, in-press manuscript, meaning that it has not officially been published yet. This raised some sticky questions about the way species are named and scientific papers are disseminated.

At Chinleana, paleontologist Bill Parker noted that the rules for naming new dinosaur species set forth by the International Commission on Zoological Nomenclature require that papers appear in print. Since we don't know when the Titanoceratops paper will be officially published, then, an unscrupulous onlooker could potentially muck up the whole process by rushing a description of the same animal into print by another route. This problem was also pointed out earlier last month by paleontologist Andy Farke, where he provided several examples of "zombie nomenclature" in which new species were described in online publications before becoming officially recognized.

Having pre-print papers is advantageous because it speeds up the dissemination of scientific ideas, but it can also be a risky move for authors. This issue could be resolved if the body charged with overseeing species names, the ICZN, changed their practices regarding electronic publications, but as Farke notes, this would be a bureaucratic nightmare that may take years to sort out. Something will have to change, though. I hope the transition will be sparked by the recognition that journals need to come to grips with online publication and not by an unfortunate case of claim-jumping.

References:

Longrich, N. (2010). Titanoceratops ouranous, a giant horned dinosaur from the Late Campanian of New Mexico Cretaceous Research DOI: 10.1016/j.cretres.2010.12.007

Riley Black | | READ MORE

Riley Black is a freelance science writer specializing in evolution, paleontology and natural history who blogs regularly for Scientific American.