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Monoclonius

2007 Schools Wikipedia Selection. Related subjects: Dinosaurs

                   iMonoclonius

                             Conservation status

   Extinct (fossil)
            Scientific classification

   Kingdom:    Animalia
   Phylum:     Chordata
   Class:      Sauropsida
   Superorder: Dinosauria
   Order:      Ornithischia
   Suborder:   Marginocephalia
   Infraorder: Ceratopsia
   Family:     Ceratopsidae
   Genus:      Monoclonius
               Cope ( 1876)

                                   Species

   See text.

   Monoclonius (meaning "single stem"; referring to the teeth, which have
   a single root) Cope 1876 was a ceratopsian dinosaur from the Judith
   River Formation of Late Cretaceous Montana and Canada. It is often
   confused with Centrosaurus, a similar species of ceratopsian (some
   think the two may even be the same, of a different age or sex).

History

   Monoclonius was Edward Drinker Cope's third named ceratopsian (after
   Agathaumas and Polyonax) and the only one of the three that has any
   validity. The type specimen was found in the summer of 1876 in Montana,
   only about 100 miles from the site of the Battle of the Little Bighorn
   that June. Although it was not an articulated skeleton, Cope recovered
   most of the animal (only the feet were entirely missing), including
   skull material and the base part of a long nasal horn. Since the
   ceratopsians were still unknown, Cope was uncertain about much of the
   skull material, not recognizing the horn core as being such.

   After O. C. Marsh's description of Triceratops in 1889, Cope reexamined
   his Monoclonius specimen and realized what it and Agathaumas were. In
   the same paper that Cope examined M. crassus, he also named three more
   Monoclonius species. He described Monoclonius as having a large nasal
   horn and two smaller horns over the eyes and a large frill ( parietal)
   with broad openings.

   Later, John Bell Hatcher (one of Marsh's workers and therefore in the '
   Yale Camp' of the Bone Wars), in continuing Marsh's monograph on the
   Ceratopsidae, derided Cope's collecting methods. Cope rarely identified
   specimens in the field with precise locations and often ended up
   describing composites, rather than single individuals. Hatcher
   reexamined the type specimen of M. crassus and the only skull remains
   that he could positively assign to this specimen was the left half of
   the parietal (dorsal part of the neck frill). He could not assign any
   of the several squamosals (side of the frill) in the collection to the
   type specimen and did not believe that Cope's orbital horn ( catalogued
   under a different number) belonged to it.

Centrosaurus intrudes

   In the years after Cope's 1889 paper, it appears that there was a
   tendency to describe everything from the Judith River beds as
   Monoclonius. The first dinosaur species described from Canada were
   ceratopsians in 1902 by Lawrence Lambe, including 3 new species of
   Monoclonius based on fragmentary skulls.

   In 1904, Lambe described Centrosaurus, based on a second specimen (a
   skull in better condition than the first) that he had attributed to
   Monoclonius dawsoni in 1902. With newer specimens collected by Charles
   H. Sternberg, it became clear that Centrosaurus was distinctly separate
   from Monoclonius, at least to Lambe. In a 1914 paper, Barnum Brown
   reviewed Monoclonius and Centrosaurus, dismissing most of Cope's
   species, leaving only M. crassus. Comparing Monoclonius to
   Centrosaurus, he determined that the M. crassus specimen had been that
   of an old animal and damaged by erosion and that the two were
   synonymous. In 1915, Lambe answered Brown in another paper (this is the
   review of Ceratopsia in which Lambe established three families),
   transferring M. dawsoni to Brachyceratops and M. sphenocerus to
   Styracosaurus. This left M. crassus, which he considered
   non-diagnostic, largely due to its damage and the lack of a nasal horn.
   Lambe ended the paper by attributing Brown's M. flexus to Centrosaurus
   apertus (the type species of Centrosaurus). The next round fell to
   Brown in a paper on Albertan centrosaurines, which, for the first time,
   analyzed a complete ceratopsian skeleton, which he named Monoclonius
   nasicornis (he contributed to the confusion even more by describing yet
   another species, M. cutleri).

   The matter bounced back and forth, over the next few years, until
   Richard Swann Lull published his "Revision of Ceratopsia", in 1933.
   Although, unlike the beautifully illustrated 1907 monograph, it has
   relatively few illustrations, it is known for the attempt to identify
   and locate all ceratopsian specimens then known. Lull described another
   specimen from Alberta (YPM 2015; Monoclonius (Centrosaurus) flexus) and
   decided that Centrosaurus was a junior synonym of Monoclonius, perhaps
   distinct enough to deserve subgeneric rank. (This specimen is exhibited
   at Yale's Peabody Museum in an unusual way: the left half shows the
   skeleton, but the right side is a reconstruction of the living animal.)
   Charles M. Sternberg, son of the above, in 1940 firmly established the
   existence of Monoclonius-type forms in Alberta (no further specimens
   have come from Montana since 1876) and showed that differences
   justified the separation of the two genera. Monoclonius-types are rarer
   and found in earlier horizons than Centrosaurus-types, seemingly
   indicating that the one is probably ancestral to the other.

Classification

   Monoclonius belonged to Centrosaurinae subfamiliy within the Ceratopsia
   (the name is Greek for "horned face"), a group of herbivorous dinosaurs
   with parrot-like beaks which thrived in North America and Asia during
   the Cretaceous Period, which ended roughly 65 million years ago. All
   ceratopsians became extinct at the end of this era.

Species

   Type:
     * Monoclonius crassus Cope 1876 [AMNH 3998]

   Other Species:
     * M. albertensis (Lambe, 1913/Leahy, 1987); included with
       Styracosaurus albertensis.
     * M. apertus (Lambe, 1904/Kuhn, 1964); included with Centrosaurus
       apertus.
     * M. belli (Lambe, 1902); included with Chasmosaurus belli.
     * M. canadensis (Lambe, 1902); included with Chasmosaurus canadensis.
     * M. cutleri (Brown, 1917); back half of skelton with some skull
       fragments, included with Centrosaurus apertus.
     * M. dawsoni (Lambe, 1902; including Brachyceratops dawsoni and
       Centrosaurus dawsoni), included with Centrosaurus apertus.
     * M. fissus Cope, 1889; isolated pterygoid (Cope identified it as a
       squamosal); nomen nudum .
     * M. flexus (Brown, 1914); included with Centrosaurus apertus.
     * M. longirostris (Sternberg, 1940/Kuhn, 1964); included with
       Centrosaurus apertus.
     * M. lowei (Sternberg, 1940); a large, somewhat flattened, skull,
       apparently that of a subadult (sutures are not completely closed).
       Sternberg pointed out the resemblances of this specimen to
       Brachyceratops
     * M. montanensis (Gilmore, 1914); included with Brachyceratops
       montanensis.
     * M. nasicornis (Brown, 1917); included part with Centrosaurus
       apertus and part with Styracosaurus albertensis (Dodson believes
       this is actually the female of Styracosaurus)
     * M. recurvicornis Cope, 1889; braincase, 3 horns and isolated
       fragments; nomen nudum included with Ceratops recurvicornis.
     * M. sphenoceras Cope, 1890; nasal horn and premaxilla; nomen nudum
       including Agathaumas sphenoceras, A. monoclonius and Styracosaurus
       sphenoceras).

Diet & Ecology

   Monoclonius, like all Ceratopsians, was a herbivore. During the
   Cretaceous, flowering plants were "geographically limited on the
   landscape", so it is likely that this dinosaur fed on the predominant
   plants of the era: ferns, cycads and conifers. It would have used its
   sharp Ceratopsian beak to bite off the leaves or needles.
   Retrieved from " http://en.wikipedia.org/wiki/Monoclonius"
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