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Mercuriceratops, new chasmosaurine ceratopsian from Montana and Alberta



From: Ben Creisler
bcreisler@gmail.com

A new dinosaur taxon:

Michael J. Ryan, David C. Evans, Philip J. Currie & Mark A. Loewen (2014)
A new chasmosaurine from northern Laramidia expands frill disparity in
ceratopsid dinosaurs.
Naturwissenschaften (advance online publication)
DOI: 10.1007/s00114-014-1183-1
http://link.springer.com/article/10.1007/s00114-014-1183-1

[Mercuriceratops gemini]

A new taxon of chasmosaurine ceratopsid demonstrates unexpected
disparity in parietosquamosal frill shape among ceratopsid dinosaurs
early in their evolutionary radiation. The new taxon is described
based on two apomorphic squamosals collected from approximately time
equivalent (approximately 77 million years old) sections of the upper
Judith River Formation, Montana, and the lower Dinosaur Park Formation
of Dinosaur Provincial Park, Alberta. It is referred to Chasmosaurinae
based on the inferred elongate morphology. The typical chasmosaurine
squamosal forms an obtuse triangle in dorsal view that tapers towards
the posterolateral corner of the frill. In the dorsal view of the new
taxon, the lateral margin of the squamosal is hatchet-shaped with the
posterior portion modified into a constricted narrow bar that would
have supported the lateral margin of a robust parietal. The new taxon
represents the oldest chasmosaurine from Canada, and the first
pre-Maastrichtian ceratopsid to have been collected on both sides of
the Canada–US border, with a minimum north–south range of 380 km. This
squamosal morphology would have given the frill of the new taxon a
unique dorsal profile that represents evolutionary experimentation in
frill signalling near the origin of chasmosaurine ceratopsids and
reinforces biogeographic differences between northern and southern
faunal provinces in the Campanian of North America.