A new species of ceratopsid (horned) dinosaur has been identified from bones discovered a decade ago in the Judith River Formation in Montana.
An artist’s rendering of Spiclypeus shipporum. Image credit: Mike Skrepnick.
The species, named Spiclypeus shipporum by Dr. Jordan Mallon from the Canadian Museum of Nature and co-authors who documented it, lived in North America about 76 million years back.
“Spiclypeus is a combination of two Latin words meaning ‘spiked shield,’ referring to the impressive head frill and triangular spikes that adorn its margins,” the scientists explained.
“The name shipporum honors the Shipp family, on whose land the fossil was found near Winifred, Montana.”
Spiclypeus shipporum belonged to a group of dinosaurs called ceratopsids (Ceratopsidae), which were herbivorous dinosaurs with horns and huge neck frills.
“Ceratopsidae is a clade of megaherbivorous dinosaurs that arose during the Late Cretaceous and rapidly diversified in Asia and North America to become one of the most speciose dinosaur groups of their time,” Dr. Mallon and co-authors said.
“Ceratopsids are most easily distinguished by their horned crania and expansive parietosquamosal frills, which were typically ornamented for display.”
About half of Spiclypeus shipporum’s skull, as well as parts of the dinosaur’s legs, hips and backbone had been preserved in the silty hillside that once formed part of an ancient floodplain.
What sets this species apart from other ceratopsids such as Triceratops is the orientation of the horns over the eyes, which stick out sideways from the skull.
There is also a unique arrangement to the bony ‘spikes’ that emanate from the margin of the frill — some of the spikes curl forward while others project outward.
“This dinosaur is special because of the shape of its horns and frill. The sideways projection of the brow horns is uncommon, and the arrangement of the frill spikes is unique: near the midline they curl forward, while the others radiate outward,” the paleontologists said.
“Spiclypeus shipporum is transitional between more primitive forms in which all the spikes at the back of the frill radiate outward, and those such as Kosmoceratops in which they all curl forward,” Dr. Mallon said.
Skull reconstruction of Spiclypeus shipporum: the darker color indicates the portions of the skull that preserved and were collected. The skull is 2.54 m long x 1.22 m wide x 1.16 m high. Image credit: Mallon J.C. et al.
The remains also tell us much about this individual’s life history, which was rife with suffering — an upper arm bone shows significant deformities from arthritis and osteomyelitis (bone infection).
“If you look near the elbow, you can see great openings that developed to drain an infection,” Dr. Mallon said.
“We don’t know how the bone became infected, but we can be sure that it caused the animal great pain for years and probably made its left forelimb useless for walking.”
Despite this trauma, analysis of the annual growth rings inside the dinosaur’s bones by the team suggests it lived to maturity. The dinosaur would have been at least 10 years old when it died.
“There are now nine well-known dinosaur species — including Spiclypeus shipporum — from Montana’s Judith River Formation,” the scientists said.
“Some are also found in Alberta, which has a much richer fossil record, but others such as Spiclypeus shipporum are unique to Montana.”
“None of the species are shared with more southerly states, suggesting that dinosaur faunas in western North America were highly localized about 76 million years ago.”
The results were published online May 18, 2016 in the journal PLoS ONE.
_____
Mallon J.C. et al. 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
