Monoclonius
Name:
Monoclonius
(Single sprout).
Phonetic: Mon-oh-clo-nee-us.
Named By: Edward Drinker Cope - 1876.
Synonyms: Monoclonius lowei?
Classification: Chordata, Reptilia, Dinosauria,
Ornithichia, Ceratopsidae, Centrosaurinae.
Species: M. crassus
(type), M. lowei?
Diet: Herbivore.
Size: Unknown.
Known locations: USA, Montana. Possibly Canada.
Time period: Late Cretaceous.
Fossil representation: Partial skull and cervical
(neck) vertebrae.
So
the taxonomic history of Monoclonius goes a little
something like
this. In 1876 multiply dinosaur fossils were recovered from the
Judith River in Montana, USA. These fossils were sent to Edward
Drinker Cope (One of the two main figures in the Bone Wars) and
from these two new dinosaur genera were named, Monoclonius
and
Diclonius. Cope believed that both of these
dinosaurs were hadrosaurs
and gave them names which meant ‘single sprout’ and ‘double
sprout’, a reference to the observation that Monoclonius
had a
single row of teeth in use at any one time, and Diclonius
had two
rows.
In
1889 Othniel Charles Marsh (The other main figure in the Bone
Wars) named what would become one of the most famous dinosaurs of all
time, Triceratops.
Cope made a point to keep up to date with
Marsh’s work, and when he saw the work on Triceratops,
he realised
that he himself had made a mistake. Going over his fossils of
Monoclonius, as well as an earlier genus named Agathaumus
that he
had also named, Cope realised that these two genera when combined
with Triceratops would actually represent a whole
new group of what
would later become known as ceratopsian
dinosaurs.
When
Cope had first named Monoclonius he was unsure how
to piece it
together, resulting in the incorrect identification of it being a
hadrosaur. Now armed with the knowledge of Triceratops
however,
Cope re-assembled his Monoclonius fossils,
identifying the horn
core, neck frill, and cervical (neck) vertebrae, which he
originally thought were dorsal (back) vertebrae. This resulted in
a re-description published later in 1889, which saw Monoclonius
reconstructed as a ceratopsian dinosaur with a single large horn rising
up from its nasal bone. However cope achieved this by adding
additional fossil specimens to his existing Monoclonius
fossils. This
was also the start of the confusion about the meaning of the name
Monoclonius with many people interpreting it as
meaning ‘single
horn’ when in fact it still meant ‘single sprout’ with a
continued reference to the teeth.
After
this Monoclonius became what is known as a
‘wastebasket taxon’,
with any other slightly similar ceratopsian fossils being assigned to
Monoclonius. Even when the fossils were clearly
different, they
would simply become a new species, and eventually the Monoclonius
genus would attain nearly twenty species. Perhaps the main reason why
this happened is because what we now call the centrosaurine
ceratopsians commonly have single large horns, and short neck
frills, just like what Monoclonius was perceived
to have had.
In
1895 Cope sold much of his fossil collection to the American Museum
of Natural History in order to keep funding his work (The Bone Wars
had a terrible effect upon the personal finances of both Cope and
Marsh). After the deaths of both Cope and Marsh, John Bell
Hatcher, a former worker of Marsh’s was assigned the task of
completing Marsh’s unfinished monograph on ceratopsian dinosaurs,
this time including Copes fossils. When Hatcher got round to the
type specimen of Monoclonius, he concluded that
it was actually based
upon the fossils of several dinosaurs, not all of them necessarily
representing the same individual. This was finally published in
1907 after hatcher himself died and the monograph was finished by
Richard Swann Lull.
This
was not the beginning of serious doubts about the Monoclonius
genus,
in 1904, fossils of two species were used to create a new genus
called Centrosaurus,
which is today the type genus of the
Centrosaurinae. Other former species of Monoclonius
have now been
largely re-assigned into other genera including Avaceratops,
Brachyceratops,
Chasmosaurus,
Eoceratops and Styracosaurus,
while fossils that were not have often been described as too
indeterminate.
Palaeontologists
have always been at odds over how valid Monoclonius
is however.
Lawrence Lambe considered Centrosaurus to be very
distinct from
Monoclonius, while Barnum Brown thought that all Monoclonius
species
named at that time were synonymous with the type species that had been
based upon eroded fossils. In 1933 Richard Lull published a paper
citing that Centrosaurus should be a sub genus to Monoclonius,
while
in 1938 Charles Mortram Sternberg claimed that Monoclonius
fossils
were slightly older than Centrosaurus fossils,
and that Monoclonius
was a probable ancestor to Centrosaurus. In
1990 Peter Dodson
noted a clear difference in the parietal bone, while a 1997
study (Sampson et al) concluded that all remaining Monoclonius
fossils were dubious because analysis of the bone indicated that they
were either juveniles or subadults. A counter paper in 1998 by
Dodson and Tumarkin was of the opinion that these juvenile features
had been retained in adulthood, and noted that one of the M.
lowei holotype had the longest known interparietal bones of
any
centrosaurine ceratopsian dinosaur. A 2006 paper by Michael Ryan
however confirmed that the holotype skull of M. lowei
was indeed a
subadult, though one of exceptional size.
With
the history behind us, the state of Monoclonius
at the time of
writing is that it is usually treated as a dubious genus of ceratopsian
dinosaur by most authors. This is because the remains of the type
species M. crassus are not very diagnostic,
which makes it
difficult to establish the holotype of the species M. lowei
with
certainty, though it has also been considered to be synonymous with
the type species. With the history done with, there really isn’t
that much more to say about Monoclonius, though
briefly going on the
assumption that Monoclonius does actually represent
a valid genus,
then Monoclonius would have been a mid-sized
centrosaurine ceratopsian
dinosaur, perhaps most similar to Centrosaurus in
form.
In
popular science and fiction Monoclonius was once
one of the staple
ceratopsian dinosaurs that would be included in works about dinosaurs,
sometimes even rivalling Triceratops and Styracosaurus
for
popularity. The most iconic appearance of Monoclonius
in recent times
was in the 1984 classic short Prehistoric Beast, a go motion
animation which featured an encounter between a Monoclonius
and a
Tyrannosaurus,
and something that is well remembered by anyone who
grew up in the 1980s.
Further reading
- Descriptions of some vertebrate remains from the Fort Union Beds of
Montana. - Proceedings of the Academy of Natural Sciences of
Philadelphia 28: 248-261. - Edward Drinker Cope - 1876.
- On Reptilian remains from the Dakota Beds of Colorado. -
Paleontological Bulletin, 26: 193-197. - Edward Drinker Cope
- 1877.
- The horned Dinosauria of the Laramie. - American Naturalist,
23: 715-717. - Edward Drinker Cope - 1889.
- New genera and species from the Belly River Series
(mid-Cretaceous). - Geological Survey of Canada Contributions to
Canadian Palaeontology 3(2): 25-81. - Lawrence M. Lambe
- 1902.
- On the squamoso-parietal crest of the horned dinosaurs Centrosaurus
apertus and Monoclonius canadensis from
the Cretaceous of Alberta. -
Transactions of the Royal Society of Canada, series 2
10(4): 1-9. Lawrence M. Lambe - 1904.
- The Ceratopsia - Monographs of the United States Geological
Survey 49, 198 pages. - O. C. Marsh, J. B. Hatcher
& R. S. Lull - 1907.
- A complete skull of the horned dinosaur Monoclonius,
from the
Belly River of Alberta. - Bulletin of the American Museum of
Natural History, 33: 549–558. - Barnum Brown - 1914.
- On Eoceratops canadensis, gen. nov., with remarks on other
genera of Cretaceous horned dinosaurs. - Canada Geological Survey
Museum Bulletin 12, Geological Series 24: 1-49. - Lawrence
M. lambe - 1915.
- A complete skeleton of the horned dinosaur Monoclonius,
and
description of a second skeleton showing skin impressions. -
Bulletin of the American Museum of Natural History, 35:
709–716. - Barnum Brown - 1917.
- A revision of the Ceratopsia or horned dinosaurs. - Memoirs of
the Peabody Museum of Natural History 3(3): 1-175. -
Richard S. Lull - 1933.
- Monoclonius from southeastern Alberta compared
with Centrosaurus.
- Journal of Palaeontology, 12(3): 284-286. - C. M.
Sternberg - 1938.
- The ceratopsian subfamily Chasmosaurinae: sexual dimorphism and
systematics - T. M. Lehman - In. Dinosaur Systematics:
Perspectives and Approaches pp211-229, Cambridge University Press
- Kenneth Carpenter & Philip J. Currie - 1990.
- On the status of the ceratopsids Monoclonius
and Centrosaurus -
P Dodson - In. Dinosaur Systematics: Perspectives and
Approaches pp211-229, Cambridge University Press - Kenneth
Carpenter & Philip J. Currie - 1990.
- Why Monoclonius Cope Was Not Named for Its
Horn: The Etymologies
of Cope's Dinosaurs. - Journal of Vertebrate Paleontology
(Journal of Vertebrate Paleontology, Vol. 12, No. 3) 12
(3): 313–317. - B. S. Creisler - 1992.
- Craniofacial ontogeny in centrosaurine dinosaurs (Ornithischia:
Ceratopsidae): taxonomic and behavioral implications. -
Zoological Journal of the Linnean Society, 121: 293–337. -
S. D. Sampson, M. J. Ryan & D. H. Tanke -
1997.
- A heterochronic analysis of enigmatic ceratopsids. - Journal of
Vertebrate Paleontology, 18(supplement): 83A. - A. R.
Tumarkin & P. Dodson - 1998.
- The status of the problematic taxon Monoclonius
(Ornithischia:
Ceratopsidae) and the recognition of adult-sized dinosaur taxa. -
Geological Society of America Abstracts with Programs, 38(4):
62. - Michael J. Ryan - 2006.
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