I mean, if you start including insects the tree on land is way deeper. There's more size niches in land photosynthesizers for whatever reason, so there's more variety in herbivore size too.
Interesting, I don't think it's true on the extremes but I reckon that is true when you think of the abundance of megafaunal herbivores on land, like there's a dugong and a few decent sized fishes, but there's no proliferation of deer, goats, rhino giraffe etc.
Not true at the extremes I say because pelagic ecosystems have small single cells handling their primary productivity, you have microscopic copepods starting the grazing at the same size as the smallest herbivorous insects, and until recently you had stellars sea cow weighing in at 8-10 t, more than an African elephant.
Not true at the extremes I say because pelagic ecosystems have small single cells handling their primary productivity, you have microscopic copepods starting the grazing at the same size as the smallest herbivorous insects, and until recently you had stellars sea cow weighing in at 8-10 t, more than an African elephant.