Answer:
Since neither reptile could have swum great distances across salt water he inferred that they once lived on a single landmass that has since split apart.
Answer:
<u><em>River valley civilizations</em></u>
Explanation:
They were centred around various river valleys as their main source of livelihood and the flourished only due tiote river valley on which they were based. Like the harappan in Indus Valley, The yellow river (Huang He), the Mesopotamia around Tigris and Euphrates and the egyptian Nile.
You can easily google this.