THE BEAKED DINOSAURS (Concluded.)
D. THE HORNED DINOSAURS, TRICERATOPS, ETC.
_Sub-Order Ceratopsia._
In 1887 Professor Marsh published a brief notice of what he supposed
to be a fossil bison horn found near Denver, Colorado. Two years later
the explorations of the lamented John B. Hatcher in Wyoming and
Montana resulted in the unexpected discovery that this horn belonged
not to a bison but to a gigantic horned reptile, and that it belonged
not in the geological yesterday as at first thought, but in the far
back Cretacic, millions of years ago. For Mr. Hatcher found complete
skulls, and later secured skeletons, clearly of the Dinosaurian group,
but representing a race of dinosaurs whose existence, or at least
their extraordinary character, had been quite unsuspected. It appeared
indeed that certain teeth and skeleton bones previously discovered by
Professor Cope were related to this new type of dinosaur, but the
fragments known to the Philadelphia professor gave him no idea of what
the animal was like, although with his usual acumen he had discerned
that they differed from any animal known to science and registered
them as new under the names of _Agathaumas_ 1873 and _Monoclonius_
1876. Professor Marsh re-named his supposed bison "_Ceratops_" (_i.e._
"horned face") and gave to the closely related skulls discovered by
Mr. Hatcher the name of _Triceratops_ (_i.e._ "three horned face"),
while to the whole group he gave the name of Ceratopsia.
[Illustration: Fig. 37.--Skulls of Horned Dinosaurs. The lower
row, _Ceratops_, _Styracosaurus_, _Monoclonius_, are from the
Middle Cretacic (Belly River formation) of Alberta;
_Anchiceratops_ is from the Upper Cretacic (Edmonton formation) of
Alberta; _Triceratops_ and _Torosaurus_ from the uppermost
Cretacic (Lance formation) of Wyoming.]
These were the first of a long series of discoveries which through
scientific and popular descriptions have made the Horned Dinosaurs
familiar to the world. Most of them are still very imperfectly known,
and of their evolution and earlier history we know very little as yet.
But we can form a fairly correct idea of their general appearance and
habits and of the part they played in the world of the late Cretacic.
So far as known they were limited to North America. The most striking
feature of the Horned Dinosaurs is the gigantic skull, armed with a
pair of horns over the orbits and a median horn on the nasal bones in
front, and with a great bony crest projecting at the back and sides.
In some species the skull with its bony frill attains a length of
seven or even eight feet and about three feet width; the usual length
is five or six feet and the width about three. In the best known
genus, _Triceratops_, the paired horns are long and stout and the
front horn quite short or almost absent, while in _Monoclonius_ these
proportions are reversed, the front horn being long while the paired
horns are rudimentary.
The teeth are in a single row but are broadened out into a wide
grinding surface. The animal was quadrupedal, with short massive limbs
and rounded elephantine feet tipped with hoofs, three in the hind
foot, four in the fore foot, a short massive tail that could hardly
reach the ground, a short broad-barrelled body and a short neck
completely hidden on top and sides by the overhanging bony frill of
the skull. In many respects these animals are suggestive far more than
any other dinosaurs, of the great quadrupeds of Tertiary and modern
times, rhinoceroses, hippopotami, titanotheres and elephants, as in
the horns they suggest the bison. For this reason although less
gigantic than the Brontosaurus or Tyrannosaurus, less grotesque
perhaps, than the Stegosaurus, they are more interesting than any
other dinosaurs. While thus departing far from the earlier type of the
beaked dinosaurs (the Iguanodonts) they are evidently descended from
them.
[Illustration: Fig. 38.--Skull of _Triceratops_ from the Lance
formation in Wyoming, one-eighteenth natural size. The length of
the horns is 2 feet, 9-1/2 inches. The rostral bone or beak, and
the lower jaw, are lacking; in the illustration on the cover they
have been restored in outline. This fine skull was discovered by
George M. Sternberg, and purchased for the Museum by Mr. Charles
Lanier in 1909.]
TRICERATOPS.
This is the best known of the Horned Dinosaurs, as various skulls and
partial skeletons have been found from which it has been possible to
reconstruct the entire animal. There is a mounted skeleton in the
National Museum, another will shortly be mounted in the American
Museum, and there are skulls in several American and European
museums.
_Triceratops_ exceeded the largest rhinoceroses in bulk, equalling a
fairly large elephant, but with much shorter legs. The great horns
over the eyes projected forward or partly upward; in one of our skulls
they are 33-1/2 inches long. During life they were probably covered
with horn increasing the length by six inches or perhaps a foot. The
ball-like condyle for articulation of the neck lies far underneath, at
the base of the frill, almost in the middle of the skull.
[Illustration: Fig. 39.--Skull of _Monoclonius_, a horned dinosaur
from the Cretacic (Belly River formation) of Alberta.
One-fifteenth natural size. The horns over the eyes are
rudimentary, and the nasal horn large, reversing the proportions
in _Triceratops_.]
_Monoclonius, Ceratops, etc._ The _Triceratops_ and another equally
gigantic Horned Dinosaur, _Torosaurus_, were the last survivors of
their race. In somewhat older formations of Cretacic age are found
remains of smaller kinds, some of them ancestors of these latest
survivors, others collaterally related. None of these have the bony
frill completely roofing over the neck as it does in _Triceratops_.
There is always a central spine projecting backwards and widening out
at the top to the bony margin of the frill which sweeps around on each
side to join bony plates that project from the sides of the skull top.
This encloses an open space or "fenestra," so that the neck was not
completely protected above. Sometimes the margin of the frill is
plain, at other times it carries a number of great spikes, like a
gigantic Horned Lizard (_Phrynosoma_).
[Illustration: Fig. 40.--Outline sketch restoration of
_Triceratops_, from the mounted skeleton in the National Museum.]
In _Ceratops_ the horns over the eyes are large and the nasal horn
small. In _Monoclonius_ the nasal horn is large and those over the
eyes are rudimentary. The great variety of species that has been found
in recent years shows that these Horned Dinosaurs were a numerous and
varied race of which as yet we know only a few. Of their evolution we
have little direct knowledge, but probably they are descended from the
Iguanodonts and Camptosaurs of the Comanchic, and their quadrupedal
gait, huge heads, short tails and other peculiarities are secondary
specializations, their ancestors being bipedal, long-tailed, small
headed and hornless.
The fine skulls of _Triceratops_, _Monoclonius_, _Ceratops_ and
_Anchiceratops_ in the Museum collections illustrate the variety of
these remarkable animals. Complete skeletons of the first two genera
are being prepared for mounting and exhibition.