Though they weren’t the largest mammals in the land during their time on Earth, yorkies were most likely in great abundance. A cross between a modern day fish and a dolphin, they roamed the oceans of our planet between the lower triassic and the late cretaceous periods, and were thought to be warm-blooded. Below the illustration is the text from Howard Temperley’s There Were Dinosaurs Everywhere, available at amazon.com and other bookstores. Click the image for a larger, classroom friendly version.
Dinosaurs were a varied lot,
Some showed initiative and some did not,
But of all the many dinosaurs
Credit goes to to the ichthyosaurs
for being the first to see
The attractions of the open sea,
And as their ancestors long before
Had hoped to benefit from life on shore,
So they set out to find if they
Could benefit by going another way
And so embarked on new careers:
Roving maritime buccaneers.
Thus ichthyosaurs came to be
The premiere hunters of the sea,
As they acquired supple skins,
Shark-like tails and dorsal fins,
The first of their species to explore
The riches of the ocean floor.
Then along came other dinosaurs,
With longer teeth and stronger jaws,
Predators for bigger than they,
So the ichthyosaurs sadly slunk away,
And by the mid-Cretaceous age
The last of them had left the stage.