The Dinosaurs of Wyoming - Wyoming State Geological Survey ...

CHAPTER XIX
Animals Which Lived with the Dinosaurs
In relating the association of Mesozoic animals with the
dinosaurs we shall speak more fully about the back-boned
animals. The lower groups of animals, called invertebrates,
were present in abundance in fresh waters and in the seas.
The only possible relation between invertebrates and dinosaurs
is that the former may have furnished the reptiles with
food, although the majority of known dinosaurs were plant
feeders, living on soft verdure along the lakes, marshes and
rivers, or on higher land, cropping leaves and twigs of such
trees and bushes as still exist, for, by the close of the Age of
Reptiles, flowering plants, woody trees, grasses and other
plants had assumed a modern aspect. The poplar, willow,
oak and maple were trees then as now.
The fishes were abundant throughout the Mesozoic, but
were mostly marine. Only three kinds of lung-fishes (dipnoans),
at present found in Africa, have been made known
from the Dinosaur beds. "0.'e do not know that the fishes
were important to the dinosaurian reptiles.
Mesozoic amphibians are few, and scantily known. Some
years ago I reviewed our knowledge of the frogs and salamanders
of the Age of Dinosaurs-but they hardly differ from
the frogs and mud-puppies which we see today. -
Birds are known from American dinosaur beds only by
fragments. I am showing here (Figure 46) a Mesozoic bird,
combining many characters. Marine birds, large wingless,
toothed, aquatic, fish-eating types and small, winged, toothed,
possibly fish-eating birds, about the size of a pigeon, are
known from the Kansas chalk.
The distinguishing character of all birds, ancient and modern,
is the possession of feathers. No other animal has them.
Birds may have arisen from reptiles, but those reptiles are
yet unknown, nor do we know the stages in the derivation of
feathers from scales. Bird fossils are among the rarest gems
of paleontology, but vve know a few complete fossil birds, some
fossil feathers and a few fossil eggs.
Before the close of the mesozoic turtles had diversified
into land-living, marine, and river or swamp turtles.
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