In the movie Pacific Rim, a Kaiju's resembles the earth's dinosaurs(except the dinosaurs lay eggs). It also resembles rhinoceros with its hard skin and the Godzilla. Which creature(s) inspired its design the most?
Oddly, it's essentially the opposite of what you're looking for. Their aim was to not mimic existing creatures or monsters, their goal was to come up with new, alien intimidating creatures:
"[Director] Guillermo del Toro wanted original designs that would redefine the genre," says Barlowe... In particular, del Toro really wanted the team of creature designers to steer clear of homages to earlier monsters or other films.
At the same time, these creatures aren't supposed to look like any Earth creatures at all — even though some early designs have a bit of hammerhead shark or bat wings in them. "It was not Guillermo del Toro's intent to evoke Earth creatures with the kaiju," says Barlowe. When del Toro was doing his monster "American Idol" to choose the best monsters, "the vetting process was based solely on what would look intimidating to the viewer," he says — so if there was a particularly scary creature that had an analogue on Earth, it did [sic] get advanced on that basis alone.
That "[sic]" marks what I'm pretty sure is a typo, there's likely a missing "not" there.