Size and Weight:
Ceratosaurus is one of those Jurassic dinosaurs that gives paleontologists fits: although it bore a distinct resemblance to other large theropods of its day (notably Allosaurus, the most common predator of Jurassic North America), it also had some anatomical quirks--such as the line of bony plates along its back--that weren't shared by any other predators. For this reason, Ceratosaurus is usually assigned to its own infraorder, ceratosauria, and dinosaurs that resemble it are classified as "ceratosaurs."
Whatever its place in the theropod family tree, it's clear that Ceratosaurus was a fierce predator, gobbling up pretty much anything it happened across--including fish, aquatic reptiles, and both herbivorous and carnivorous dinosaurs. The marine part of its diet can be explained by the fact that Ceratosaurus had a more flexible tail than other carnivores, allowing it to swim with greater agility.