I highly recommend the book "Ghosts of Evolution" about the lingering effects of these extinct megafauna on our lives today. Many of our ecosystems and even many species evolved in response to their presence.
A major theme of the book is how many of the fruits we see today (especially avocados, osange oranges, honey locust pods, possibly mangoes and many other large fruits) originally evolved to be eaten by megafauna. The idea is they would eat the fruit whole and swallow the pit, and poop it out somewhere. Evidence for this is that many of the trees have defenses against non-megafauna eating the fruits, or others have out-of-proportion defenses against any living animal today, the fact that many pits will only grow if they have been scoured (for example by the digestive system of an animal), and that the pits often seem over-defended, and the fact that many of these fruits are not eaten by any living animals and often fall from the tree and rot in place.
A major theme of the book is how many of the fruits we see today (especially avocados, osange oranges, honey locust pods, possibly mangoes and many other large fruits) originally evolved to be eaten by megafauna. The idea is they would eat the fruit whole and swallow the pit, and poop it out somewhere. Evidence for this is that many of the trees have defenses against non-megafauna eating the fruits, or others have out-of-proportion defenses against any living animal today, the fact that many pits will only grow if they have been scoured (for example by the digestive system of an animal), and that the pits often seem over-defended, and the fact that many of these fruits are not eaten by any living animals and often fall from the tree and rot in place.