Interesting article. I highly recommend the book "The Ghosts of Evolution" by Connie Barlow, it's about the concept of ecological anachronisms. Mainly it's about plants whose seed dispersal is best accomplished by megafauna, osage-orange is an extreme example of this. It was almost extinct when the first white settlers found it (and subsequently planted it all over as a living fence before barbed wire). So now it's reclaimed much of it's original range, which they know used to be pretty large from pollen sediments. No native animal disperses the seeds, squirrels pick apart the fruit to get to the seeds but don't spread them anywhere. Some sorts of megafauna would have eaten the fruits whole and spread the seeds far and wide. Pawpaw and honeylocust are less extreme examples of anachronistic fruit.
The book also goes into come things besides fruit, such as thorns. Hawthorn thorns are too far apart to deter deer, which just nibble around them, but a larger browser that takes in whole twigs at a time wouldn't want to mess with it. Honeylocust and holly trees have thorns at the base but not toward the top, but they go up 20 feet or so, much higher than any animal that's been here since the Pleistocene. Even pollination may be anachronistic in such plants as the pawpaw. Their known to be poorly pollinated even in the wild natural settings. Flies are the primary pollinator now but the flower isn't shaped for optimal pollination by flies, so the theory is they may have used to attract certain beetles that were numerous when there was lots of megafaunal dung around.
One thing that book doesn't get into however is the effects that the browsing of these animals themselves must have had, considering how there's a noticable difference in the ecosystems from high deer populations, it's pretty staggering what it must have been like back when all the megafauna were around.