New species of horned dinosaur with a spiked ‘shield’

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A chance fossil discovery in Montana a decade ago has led to the identification of an audacious new species of horned dinosaur, Spiclypeus shipporum, according to a study published May 18th, 2016 in the open-access journal PLOS ONE by Jordan Mallon, from the Canadian Museum of Nature, Canada, and colleagues.

The new dinosaur, Spiclypeus shipporum, is described from bones representing the skull, part of the legs, hips and backbone of an individual preserved in a silty hillside that once formed part of an ancient floodplain. While the fossil now has a scientific name, it is more commonly known by its nickname "Judith," after the Judith River geological formation where it was found. What sets Spiclypeus shipporum apart from other horned dinosaurs is the orientation of the horns over the eyes, which stuck out sideways from the skull, and a unique arrangement of bony "spikes" that emanated from the margin of the frill–some spikes curled forward while others projected outward.

Close examination of some of its other bones may also suggest a life lived with pain. Judith's upper arm bone (humerus) showed distinct signs of arthritis and bone infection. Despite this trauma, analysis of the annual growth rings inside the dinosaur's bones suggested that it lived to maturity, and would likely have been at least 10 years old when it died.

There are now nine well-known dinosaur species from Montana's Judith River Formation, some of which were also found in Alberta, while others such as Spiclypeus are unique to Montana. The authors note that none of the species have been found in more southerly states, suggesting that dinosaur faunas in western North America may have been highly localized about 76 million years ago. Jordan Mallon's prior research has shown that such species-rich communities may have been enabled by dietary specializations among the herbivores, a phenomenon more commonly known as niche partitioning.

"This is a spectacular new addition to the family of horned dinosaurs that roamed western North America between 85 and 66 million years ago," explains Mallon, who collaborated with researchers in Canada and the United States. "It provides new evidence of dinosaur diversity during the Late Cretaceous period from an area that is likely to yield even more discoveries."

The name Spiclypeus is a combination of two Latin words meaning "spiked shield," referring to the impressive head frill and triangular spikes that adorn its margins, and the name shipporum honors the Shipp family on whose land the fossil was found near Winifred, Montana by Dr. Bill Shipp.

"Little did I know that the first time I went fossil hunting I would stumble on a new species," explains Shipp, a retired nuclear physicist who became a fossil enthusiast after moving to his dinosaur rich area of Montana. "As a scientist, I'm really pleased that the Canadian Museum of Nature has recognized the dinosaur's value, and that it can now be accessed by researchers around the world as part of the museum's fossil collections."

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Adapted by PLOS ONE from release provided by the author

In your coverage please use this URL to provide access to the freely available paper: http://dx.plos.org/10.1371/journal.pone.0154218

Citation: Mallon JC, Ott CJ, Larson PL, Iuliano EM, Evans DC (2016) Spiclypeus shipporum gen. et sp. nov., a Boldly Audacious New Chasmosaurine Ceratopsid (Dinosauria: Ornithischia) from the Judith River Formation (Upper Cretaceous: Campanian) of Montana, USA. PLoS ONE 11(5): e0154218. doi:10.1371/journal.pone.0154218

Funding: The authors have no support or funding to report.

Competing Interests: The authors have declared that no competing interests exist.

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