The soft vinyl kit "T-Rex vs. Triceratops" (Photo 1) released by Aoshima in the late 80s incorporated new dinosaur imagery into a traditional showdown. While its ambition is commendable, it went a bit too far, and the T-Rex, unfortunately, ended up looking like it was in a yoga pose. In the same 80s Clover 1/50 soft vinyl dinosaur series, only the Gorgosaurus (Photo 2) had a nice forward-leaning posture (though its tail was disproportionately short and hanging low).

Speaking of new ornithischians, in addition to the horizontal posture, there's the cheek pouch. I believe the first example of this was Kaiyodo's galloping Iguanodon by Araki. Around that time, I also made things like this myself (Photo 3). It's supposed to be a Camptosaurus.
Finally, let me introduce an unorthodox Triceratops model born during the transitional period of dinosaur imagery (Photo 4). It's based on the innovative reconstruction depicted in "Dinosaurs: A New Look at the Old Dinosaurs" (McLoughlin, 1982), where the frill is covered in muscle. This theory didn't seem to be very popular, as it's not mentioned in other books, and as far as I know, this is the only model of it. It certainly looks uncool...