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Monoclonius recurvicornis..a new generic name
Monoclomius recurvicornis is one of the forgotten species named by Cope (based
on 3 horn, a braincase, and an occipital condylum); however, the generic name
is wrong: this animal was another kind of animal.
The "M." recurvicornis is often regarded as an indeterminate ceratopsid, but
the fragmentary holotype have some truly intriguing character present in no
other ceratopsid. Although the specimen is a subadult, the shape and dimension
of the horns are totally different from any other centrosaurine or
chasmosaurine. The suprahorbital horn are 210 mm high, completely erect, and
slighty procurved, totally different from Chasmosaurus (the only chasmosaurine
with short supraorbital horn), and only superficially similar to the new
Montana centrosaurine. Moreover, the orbital horn appear to be born from a
separate center of ossification (this feature would be unique in ceratopsian
kingdom). The nasal horn is a small version to that of Einiosaurus, and like
other subadult centrosaurine, the horn is split in two halves. In front of
right eyes there is an unespected formation: a small procurved hornlet; the
left side is no preserved, so one can?t tell if that horn was pathologic.
Unfortunately the frill is no preserved.
This combination of character (moderately erect suprahorbital horn, medium
sized, strongly procurved nasal horn and Maybe an extra pair of small hornlets
in the frontal) are not comparable to any known ceratopsid taxa, and probably
are diagnostic at generic level.
This animal should be renamed under another generic name, ?cause is totally
different from Monoclonius sensu stricto (indeterminate centrosaurines based on
subadult of Centrosaurus and Styracosaurus). However, the available material is
scrappy, and his relation with other ceratopsid remain unclear (without a
parietal or squamosal anyone can tell if this critter was a basal centrosaurine
or was member of the clade Chasmosaurus + Pentaceratops).
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