DINOSAURS
Chapter 9:
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.
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.
Fig. 38.—Skull of Triceratops from the Lance
formation in Wyoming, one-eighteenth natural size.
The length of the horns is 2 feet, 9½ 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 33½ 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.
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
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. |
