Baby Names Beginning With "S": Meaning: Treeless Plain?

Questions

What do the initials of the painter J M W Turner stand for?

What is the largest animal that has ever inhabited the planet Earth?

The Oubangi, Lulonga and Lamami rivers are tributaries of which river?

Holding hands at midnight, 'neath a starry sky' begins which George & Ira Gershwin song?

Tim Allerton & Linnet Doyle are characters from which Agatha Christie novel?