Plants has changed much since the time of the dinosaurs.  However, not so very much as many imagine.  Mosses, lycophytes and ferns existed long before the dinosaurs.  Cycads and conifers existed as well as deciduous trees with more or less hand fan-shaped leaves.  In addition there was a group of extinct plants called seed ferns.  The oldest fossils of flowering plants are from the early Cretaceous.  Both herbs, shrubs and trees arose relatively quickly.  These started to become common during the middle of the Cretaceous.  At the same time grasses evolved although they were not common.  One may imagine flowers coming out among seed ferns.

During the Triassic there were jungles in two areas of the world.  These were southern North America and what is now southern China.  Dense, temperate forests were found at both poles.  As Pangaea drifted northwards the largest forest area moved from the South to the North Pole.  Later during the Jurassic the long-necks become huge.  Their influence on the vegetation prevented dense forests.  Not only did animals this size need to eat loads of plants.  Where they walked around the vegetation was trampled down.  So when they spread across the world dense forests disappeared.  During the Cretaceous there were neither any but open woods were widespread.

The largest dinosaurs as such did not live in jungles.  Instead they were found in open woods, savannahs and shrublands.  Dinosaurs up to the size of an elephant could have lived in deserts too.  In contrast, few of them lived in wetlands.  During the Jurassic and the early Cretaceous there was something comparable to tundra.  Sensibly, dinosaurs of elephant size could also have survived there.  A cold climate was not a problem to most dinosaur groups.  All were more or less warm-blooded.

There were many different animals which people associate with dinosaurs.  One of them were the ichthyosaurs which origin is uncertain.  The only thing known for sure is them being descended from quadrupeds which their skeleton makes obvious.  Early forms of ichthyosaurs survived the Permian-Triassic mass-extinction.  During the course of the Triassic the plesiosaurs gradually evolved.  These then lived on during the entire age of dinosaurs.  In contrast, ichthyosaurs went extinct before that.  I think they were outcompeted by the less famous mosasaurs.  The latter were most closely related to present-day snakes and lizards.  I have previously mixed them up with short-necked plesiosaurs.

Most early reptiles more or less resembled lizards.  Turtles arose during the Triassic by way of the animals’ ribs gradually fusing into a shell.  Snakes later evolved as a group of legless lizards.  This was in the middle to late Cretaceous.  Please note that several groups of lizards have evolved limblessness since then.  Since these have arisen independently they are not considered true snakes.

Mammals already divided from reptiles before the age of dinosaurs.  Proto-mammals rapidly evolved legs which were constructed as those of crocodilians.  This meant their feet could be strait below their shoulders and hips.  However, their elbows and knees still sprawled a little to the sides.  Later strait mammalian legs evolved, first in the form of hind legs and later also front legs.  When fur evolved is more uncertain.  The cynodonts evidently had whiskers so they had to have been fur-covered.  The evolution of their teeth can be used to determine when mammary glands arose.  Those which only changed them once likely suckled as young.

When the dinosaurs took over most proto-mammals were outcompeted.  Those which survived were the ones avoiding to compete with the dinosaurs and their juveniles.  It was a matter of small animals which were mostly nocturnal.  During the rest of the age of dinosaurs there were only small and medium sized mammals.  I think the largest of them was the size of a badger.  Larger than this they did not get.

Uploaded on the 29th of August 2024.