Ok, there are several similarities.
Both are Sharpteeth.
Both attack a major character's mother and bring her down to the ground, bleeding and hurt. (In Chomper's mother's case, it luckily wasn't fatal.)
Both ended up getting injured by a major character before the final confrontation. (In the case of Sharptooth, it was his eye. In the case of the Plated Sharptooth, Chomper bit him in the tail.)
Both seem to have special jumping powers and be extra evil and kinda nuts. (In Sharptooth's case, he was snapping at air, just eager to get at the kids, even though he couldn't fit through the opening. In the Plated Sharptooth's case, he went and tore the bush where they had been, apart, even though they weren't there anymore.)
Both are foiled from killing the Gang by the timely arrival of characters at the last minute. (In the case of Sharptooth, it was Cera. In the case of the Plated Sharptooth, it was Chomper's parents.)
Both try and take someone with them before their downfall. (In Sharptooth's case: Petrie. In the Plated Sharptooth's case: Chomper.)
Both presumably drown.
Both have red eyes and green skin.
Do you think that the way the Plated Sharptooth was designed was a throwback to Sharptooth himself or am I reading too much into this?