Dinosaurs - Chronology - 127 million years ago

The Early Cretaceous period was a time of great change in animal life on land - new types of dinosaurs were appearing that would later be some of the most numerous on land - the ornithopods.

Small versions of these dinosaurs had actually been around since the Early Jurassic period, but only now did they come into their own. Iguanodon was one of the earliest of these large plant eating ornithopods; there were several species in Europe, Asia and North America.

Cheeky chewers
Although smaller than the sauropods, the ornithopods were more numerous. They were able to chew their food, and hold it in their cheeks whilst they did so. Chewing broke their food into smaller pieces, greatly reducing breakdown time. Sauropods didn't chew their food at all and so they needed huge bodies so their guts could break down food over several days. As they didn't have cheeks, they had the big reptilian smile we see in modern lizards and crocodiles.

Bird-like dinosaurs
New kinds of theropods also appeared in the Early Cretaceous period. These were the kinds popularly known as 'raptors, such as Utahraptor and Velociraptor. These theropods were some of the most bird-like dinosaurs that ever existed; they had fairly long arms and a more bird-like pelvis. Birds are descended from theropod dinosaurs like these - over a hundred characters in the skeleton link these two groups together. Fossil evidence of several of these dinosaurs associated with an ornithopod from the USA indicates that these types of dinosaurs may have hunted in packs.

The power of flight
The earliest known bird - Archaeopteryx - comes from the Late Jurassic period, in Germany. By the Early Cretaceous period birds had radiated and diversified. Fossils have been found in Spain and China. Most of these early birds look very primitive and some still have teeth. But by the Late Cretaceous period they looked look far more modern and had diversified into different niches. Some wading or diving birds had even lost their power of flight.

Giant gliders
The largest animals ever to fly were pterosaurs. With wingspans of up to 12m, they could be as big as a small modern glider. Pterosaurs were, to our eyes, a peculiar mixture of bird and bat. Their long beaks remind us of birds, but they had membraneous wings like bats.

These were attached to their legs and they walked on all fours, with an erect, rather than sprawling posture. Although not necessarily very speedy on land, they were competent, especially the tailess ones. Their tracks have been found in rocks around the world.

There are actually two kinds of pterosaurs, ones with and others without tails. The tailed pterosaurs lived from the Late Triassic period to the Late Jurassic period, when they were replaced by the tailess ones. It is this second group, including Ornithocheirus, which grew to great sizes.

A world of colour
In the plant kingdom there were great changes too. Flowering plants appeared in the Late Jurassic period, and in the Early Cretaceous period the first flowers appeared. Soon flowers and flowering plants were to become the most common plants on the earth.

The earliest known fossil flower is very small. It was found in the Wealden Formation sediments of southern England. During the Early Cretaceous period, southern England was a low-lying, richly vegetated river floodplain.
The climate was humid and sub-tropical, although their may have been wet and dry seasons, as there is evidence for forest fires. By the Late Cretaceous period the world would have looked rather more familiar to us, although there were still no grasses.