It's been a while since I noticed this, but I haven't posted about it so, yeah, here it is. I've noticed the problem is with many things, such as paleoart, and people getting in to dinosaurs, laymen, and people wanting to study dinosaurs, is that a lot of people seem to think the whole ecosystem is JUST dinosaurs, filling every niche and dominating everything. It's time to educate people that this is far from the truth. For example, if you look at the Candeleros Formation, you have the dinosaurs, like the superpredator Giganotosaurus and the unique (fine, from a unique family) heron-like Buitreraptor and the vacuum cleaner-mouthed Limaysaurus. But we have a great record of non-dinosaurians there too. For example, the primitive snake Najash, is known from this formation, as is the terrestrial Araripesuchus and the saber-toothed "squirrel" Cronopio. Sphenodontians, turtles, frogs, and fish can be found here too.
And then, when you look at Hell Creek, we have an astounding record of non-dinosaurians. Quetzalcoatlus was like a giant marabou stork, and then we have plenty of mammals too, like Alphadon and Didelphodon, which could have preyed on young dinosaurs. The formations of Early Cretaceous China show plenty of niches being occupied and reveal plenty of non-dinosaurians; the astounding amount of pterosaurs, Hyphalosaurus, Repenomamus (a near badger-sized mammal that preyed on baby dinosaurs), Xianglong, etc. In earlier Chinese rocks, we see the relatively big otter-niche Castorocauda, the flying squirrel-like Volaticotherium, and the giant spider which could have eaten baby scansoriopterygids, Nephila jurassica.
And the dinosaurs weren't stopping anything from being big either. The giant azhdarchids, Quetzalcoaltus, Hatzegopteryx (=Quetzalcoatlus?), Arambourgiania, etc, were already nearly giraffe-height with wingspans the size of small airplanes (a cliched fact in dinosaur books), and they all lived in an ecosystem with dinosaurs. Mammals also were getting big too, the aforementioned Didelphodon was the size of a Virginia opossum, Repenomamus giganticus was a meter long, as was the platypus Kollikodon (originally going to be named Hotcrossbunodon, which means it would be excluded from every book ever), and Castorocauda was the size of a female platypus. And while I've been saying "non-dinosaurians" this whole post, I want to include some birds in this too. Gargantuavis was a rhea to emu-sized bird from Late Cretaceous France, and the possible bird Samrukia was the size of a large ostrich. Lizards such as Palaeosaniwa were 6ft long, perhaps somewhat like a savannah monitor. Madtsoiia was 20-30ft long, if I recall correctly. Several terrestrial crocodiles neared 10-20ft long. It's well-known that many aquatic/semiaquatic crocodiles reached 20-40ft long, but since non-avian dinosaurs don't really dominate this niche at any point, it's safe to exclude them. Dinosaurs weren't the only big animals around.
And dinosaurs weren't the most dominant either, especially near the end of their reign. In Brazil and Pakistan, Baurusuchus and Pabweshi, respectively, overthrew the reign of dinosaurs and became 6-10ft long apex predators. Hatzegopteryx (=Quetzalcoatlus?) and Bakonydraco were the apex predators of their area, and they were pterosaurs. The aforementioned Madtsoiia could have been a contender for apex predator.
So anyways, the point of this long post that it's time to educate that dinosaurs weren't all superior. Many other creatures got big during their reign, many coexisted with them, and many were fierce contenders. Truthfully, most of the research on animals that coexisted with dinosaurs, is passed by and focused on, well, dinosaurs. It's time to educate, research, and change this view.