Animals of the Mesozoic era

The end of the Cretaceous period is marked by a major extinction event. Though not as great as the extinction event at the end of the end of the Triassic period, as many as fifty percent of the Earth s species became extinct. Nevertheless it caused the demise of the dinosaurs and was the end of the age of reptiles. Why this event occurred is contentious but there may have been an asteroid impact which created the Chicxulub crater off the Yucatan peninsula, Mexico. The pterosams, many marine reptiles, some groups of foraminifera and ammonites also became extinct. 

There were major changes in the diversity, radiation and abundance of the angiosperms. All angiosperms reproduce via organs in the flower and they appeared suddenly c. 100 x 10 years ago. Their ancestry is unclear but they evolved and occupied a wide range of ecological niches rapidly in 

Modem humans (Homo sapiens) emerged by at least c. 250,000 years ago, and possibly 400,000 years ago, in east-central Africa. Their ancestors. Homo erectus, had already expanded beyond their centre of origin to reach Europe and Asia and had begun the process of domesticating carbon by harnessing fire. Subsequently modern humans arose in Africa and proved to be particularly successful. Not only did they colonize all continents except Antarctica but they have also exerted immense influence over almost all 

Limestones Calcium carbonate organic and inorganic origin 

Evaporites Various salts e g. gypsum, halite inorganic 

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