Dinosaurs | Page 6

of Dinosaurs, illustrating the principal
types--Anchisaurus after Marsh, the others from American Museum
specimens.]
II. Amphibious Dinosaurs or Sauropoda. With blunt-pointed teeth and
blunt claws, quadrupedal, with elephant-like limbs and feet, long neck
and small head. Unarmored. Principal dinosaurs of this group in
America are Brontosaurus, Diplodocus, Camarasaurus (Morosaurus)
and Brachiosaurus, all of the Upper Jurassic and Comanchic periods.
III. Beaked Dinosaurs or Predentates. With a horny beak on the front
of the jaw, cutting or grinding teeth behind it. All herbivorous, with
pelvis of peculiar type, with hoofs instead of claws, and many genera
heavily armored. Mostly three short toes on the hind foot, four or five
on the fore foot. This group comprises animals of very different
proportions as follows:
1. Iguanodonts. Bipedal, unarmored, with a single row of serrated
cutting teeth, three-toed hind feet. Upper Jurassic, Comanchic and
Cretacic. Camptosaurus is the best known American genus.
2. Trachodonts or Duck-billed Dinosaurs. Like the Iguanodonts but
with numerous rows of small teeth set close together to form a grinding
surface. Cretacic period. Trachodon, Hadrosaurus, Claosaurus,
Saurolophus, Corythosaurus, etc.
3. Stegosaurs or Armored Dinosaurs. Quadrupedal dinosaurs with
elephantine feet, short neck, small head, body and tail armored with
massive bony plates and often with large bony spines. Teeth in a single
row, like those of Iguanodonts. Stegosaurus of the Upper Jurassic,
Ankylosaurus of the Upper Cretacic.
[Illustration: Fig. 8.--Hind Feet of Dinosaurs, to show the three chief
types (Theropoda, Orthopoda, Sauropoda).]
4. Ceratopsian or Horned Dinosaurs. Quadrupedal with elephantine
feet, short neck, very large head enlarged by an enormous bony frill
covering the neck, with a pair of horns over the eyes and a single horn

in front. Teeth in a single row, but broadened out and adapted for
grinding the food. No body armor. Triceratops is the best known type.
Monoclonius, Ceratops, Torosaurus and Anchiceratops are also of this
group. All from the Cretacic period.
Classification of Dinosaurs. It is probable that the Dinosaurs are not
really a natural group or order of reptiles, although they have been
generally so considered. The Carnivorous and Amphibious Dinosaurs
in spite of their diverse appearance and habits, are rather nearly related,
while the Beaked Dinosaurs form a group apart, and may be
descendants of a different group of primitive reptiles. These relations
are most clearly seen in the construction of the pelvis (see fig. 9). In the
first two groups the pubis projects downward and forward as it does in
the majority of reptiles, and the ilium is a high rounded plate; while in
the others the pelvis is of a wholly different type, strongly suggesting
the pelvis of birds.
[Illustration: Fig. 9.--Pelves of Dinosaurs illustrating the two chief
types (Saurischia, Ornithischia) and their variations.]
Recent researches upon Triassic dinosaurs, especially by the
distinguished German savants, Friedrich von Huene, Otto Jaekel and
the late Eberhard Fraas, and the discovery of more complete specimens
of these animals, also clear up the true relationships of these primitive
dinosaurs which have mostly been referred hitherto to the Theropoda or
Megalosaurians. The following classification is somewhat more
conservative than the arrangement recently proposed by von Huene.
ORDER SAURISCHIA Seeley. Suborder Coelurosauria von Huene
(=Compsognatha Huxley, Symphypoda Cope.) Fam. Podokesauridæ
Triassic, Connecticut. " Hallopodidæ Jurassic, Colorado. " Coeluridæ
Jurassic and Comanchic, North America. " Compsognathidæ Jurassic,
Europe. Suborder Pachypodosauria von Huene. Fam. Anchisauridæ
Triassic, North America and Europe. " Zanclodontidæ } "
Plateosauridæ } Triassic, Europe.* Suborder Theropoda Marsh
(=Goniopoda Cope) Fam. Megalosauridæ Jurassic and Comanchic. "
Deinodontidæ Cretacic. " Ornithomimidæ Cretacic, North America.
Suborder Sauropoda Marsh (=Opisthocoelia Owen, Cetiosauria Seeley.)

Fam. Cetiosauridæ } " Morosauridæ } Jurassic and Comanchic. "
Diplodocidæ } Order ORNITHISCHIA Seeley (=Orthopoda Cope,
Predentata Marsh.) Suborder Ornithopoda Marsh (Iguanodontia Dollo)
Fam. Nanosauridæ Jurassic, Colorado. " Camptosauridæ } "
Iguanodontidæ } Jurassic and Comanchic. " Trachodontidæ
(=Hadrosauridæ), Cretacic. Suborder Stegosauria Marsh. Fam.
Scelidosauridæ } Jurassic and Comanchic. " Stegosauridæ } "
Ankylosauridæ (=Nodosauridæ), Cretacic. Suborder Ceratopsia Marsh.
Fam. Ceratopsidæ Cretacic.
* Regarded by Dr. von Huene as ancestral respectively to the
Theropoda and Sauropoda.
FOOTNOTES:
[Footnote 2: If some vast catastrophe should today blot out all the
mammalian races including man, and the birds, but leave the lizards
and other reptiles still surviving, with the lower animals and plants, we
might well expect the lizards in the course of geologic periods to
evolve into a great and varied land fauna like the Dinosaurs of the
Mesozoic Era.]
[Footnote 3: The ancestral types have four complete toes, but in the
true Theropoda the inner digit is reduced to a small incomplete remnant,
its claw reversed and projecting at the back of the foot, as in birds.]
CHAPTER IV.
THE CARNIVOROUS DINOSAURS, ALLOSAURUS,
TYRANNOSAURUS, ORNITHOLESTES, ETC.
SUB-ORDER THEROPODA.
The sharp teeth, compressed and serrated like a palaeolithic spear point,
and the powerful sharp-pointed curved claws on