Did Thomas Jefferson ask Lewis and Clark to look for dinosaurs?

Answer 1

While he did not ask Lewis and Clark to look for dinosaurs, he did ask them to examine the remains of any animal they found to be rare or extinct. In other words, any fossils and/or bones. Here are Jefferson's words:

"Other objects worthy of notice will be the soil & face of the country, it's growth & vegetable productions, especially those not of the US; the animals of the country generally & especially those not known in the US; the remains & accounts of any which may be deemed rare or extinct..."