New ceratopsian - Eotriceratops xerinsularis

[Tim Williams <twilliams_alpha@hotmail.com>]

This just out...


Xiao-Chun Wu, Donald B. Brinkman, David A. Eberth, and Dennis R. Braman (2007)  
A new ceratopsid dinosaur (Ornithischia) from the uppermost Horseshoe Canyon 
Formation (upper Maastrichtian), Alberta, Canada.  Can. J. Earth Sci. 44: 
1243-1265 (2007)

Abstract: "A skeleton of a new ceratopsid dinosaur, _Eotriceratops 
xerinsularis_ gen. et sp. nov., is described in this paper.  It is the first 
associated vertebrate skeleton found within the upper 20 m of the Horseshoe 
Canyon Formation.  _Eotriceratops xerinsularis_ is a large chasmosaurine that 
differs from other chasmosaurines in a unique set of features in the 
premaxilla, nasal horn core, squamosal frill, and epijugal.  The most striking 
of those features includes an extremely tall, non-recessed narial process of 
the premaxilla; the presence of greatly elongate, spindle-shaped epoccipitals 
on the squamosal frill; a deep, well-demarcated fossa on the anteroventral 
surface of the squamosal frill; a sharply conical epijugal with a pronounced 
proximoposterior process and separate fossa-like facets for the jugal and 
quadratojugal; and the presence of an obliquely extending vascular trace 
meeting a transverse vascular trace ventrally on the anterior surface of the 
nasal horn core.  Our
 phylogenetic analysis suggests that _E. xerinsularis_ is nested within a clade 
including _Triceratops_, _Diceratops_ [sic], and _Torosaurus_, which are all 
from late Maastrichtian deposits.  The upper 20 m of the Horseshoe Canyon 
Formation comprises a coal-rich interval (Carbon–Thompson coal zone, unit 5), 
which previously has been assigned to upper Maastrichtian magnetochrons 31n and 
30r, and the _Mancicorpus gibbus_ miospore subzone.  The ceratopsid specimen 
was collected from between the Carbon and Thompson coal seams, and thus, is 
inferred to (1) occur near the top of magnetochron 31n and (2) have an age of 
67.6–68.0 Ma.  Large chasmosaurine ceratopsids, such as _Triceratops_ and 
_Torosaurus_, have not previously been described from the Horseshoe Canyon 
Formation or from magnetochron 31n or the _M. gibbus_ miospore subzone.  Thus, 
_Eotriceratops_ is distinctly older than any other ceratopsid in the 
_Triceratops_ group, and the discovery of _E. xerinsularis_ helps fill a
 biostratigraphic gap between early and late Maastri!
chtian chasmosaurines."

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