I was looking for my favorite book as a child when I stumbled across this website. It was a hardcover (thinner) book on Dinosaurs. The covers were gray, I believe it had a Tyrannosaurus Rex on the front cover, possibly in red writing.
Regretfully I don’t remember the exact title, just Dinosaurs, it was purchased around 1992.
Each page showed large depictions of each dinosaur in its natural habitat and some pictures were quite scary (or maybe that’s because I was a kid).
On the back cover or towards the back of the picture book it had a depiction of a Saber Tooth Tiger attacking or eating another dinosaur.