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RE: Monoclonius recurvicornis..a new generic name



I have often gazed at this specimen through the glass at the AMNH, with many
of your same thoughts. Frustratingly, it's totally inaccessible (sadly, more
dinosaur type specimens were lost to science during the renovation of the
AMNH's dinosaur halls than during World Wars I and II combined).

The original facial section of "Monoclonius recurvicornis" is heavily
reconstructed and covered in plaster. It's nearly impossible to tell what is
real morphology and what has been plastered over. The same goes for many of
Cope and Marsh's old ceratopsid specimens, including Triceratops alticornis.

I agree that the "extra" hornlet is interesting. Whether or not it's
taxonomically significant would require another specimen. This is certainly
not impossible. . .

The nasal horn is quite different from Einiosaurus, in that the horn of
Einiosaurus is compressed medio-laterally.

As for the rest of it, I will echo Jordan and Jaime's observations that
centrosaurines (and chasmosaurines) are so darned variable that you can't
say much about the M. recurvicornis type, other than that it's an
interesting specimen. Naming a new taxon would be hazardous at best (without
further material).

Andy

> -----Original Message-----
> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu] On Behalf Of
> heby@libero.it
> Sent: Tuesday, October 19, 2004 5:16 PM
> To: .. ...
> Subject: 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).
> 
> Lukas Panzarin
> 
> 
> 
> 
> 
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