Dinosaurs, with Special Reference to the American Museum Collections

OF DIN

d Differences Betwee

ed for a long era, estimated at nine millions of years, and about three times as long as the period which has elapsed since their disappearance. They survived vast changes in geography and climate, and became extinct through a combination of causes not fully understood

foot, tipped with sharp claws, and with a complete series of sharp pointed teeth. It would seem probable that these ancestors were mo

ize, some herbivorous, some carnivorous; some bipedal, others quadrupedal; many of them protected by various kinds

s of Dinosaurs. Scale about

Dinosaurs are customa

t, generally three-toed;[3] the fore-limbs adapted for grasping or tearing, but not for support of the body. T

tholestes-Upper

Albertosaurus, Ornithomim

he principal types-Anchisaurus after Marsh,

e limbs and feet, long neck and small head. Unarmored. Principal dinosaurs of this group in America are Brontos

erbivorous, with pelvis of peculiar type, with hoofs instead of claws, and many genera heavily armored. Mostly three short

ed cutting teeth, three-toed hind feet. Upper Jurassic, Comanch

us rows of small teeth set close together to form a grinding surface. Cretaci

d, body and tail armored with massive bony plates and often with large bony spines. Teeth in a single

to show the three chief types (T

ck, 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 bod

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

ting the two chief types (Saurischia

the discovery of more complete specimens of these animals, also clear up the true relationships of these primitive dinosaurs which have mostly been referre

urischia

on Huene (=Compsognatha

urid? Triassi

d? Jurassic

ssic and Comanch

thid? Juras

chypodosaur

Triassic, North

tid? Triass

teosa

poda Marsh (=G

rid? Jurassic

ontid? C

d? Cretacic,

sh (=Opisthocoelia Owe

rid? Jurassic

rosa

plod

eeley (=Orthopoda Co

opoda Marsh (Ig

rid? Jurassi

d? Jurassic a

anodo

? (=Hadrosauri

Stegosaur

urid? Jurassic

egos

d? (=Nodosaur

Ceratop

atopsid?

as ancestral respectively to

TNO

he lizards and other reptiles still surviving, with the lower animals and plants, we might well expect the lizards i

eropoda the inner digit is reduced to a small incomplete remnant, i