Dilophosaurus and Ceratosaurus are ceratosaurs, not carnosaurs (if you were
basing their placement in the Carnosauria by the fact that they have three
fingers, Dilophosaurus and Ceratosaurus do not, they have 5 [I think]).
Carnosaurs are only Allosaurs and close relatives (Sinraptorids,
Carcharodontosaurs). Please someone correct me if I am wrong.
Looks like it's time to over-technicalize this previously tame post :-) . It's looking more and more like ceratosaurs (as usually defined- including coelophysoids, Dilophosaurus, Ceratosaurus and abelisaurs) are not a monophyletic group, but successive outgroups to tetanurans. Although tetanuran phylogeny is currently controversial, spinosaurids were probably not carnosaurs, but instead a more primitive type of tetanuran, like megalosaurids. You are right in stating carnosaurs include allosaurids, sinraptorids and carcharodontosaurids (and perhaps some more primitive taxa like Monolophosaurus and Fukuiraptor...). As far as how many fingers these things had.... All "ceratosaurs" and non-coelurosaurian tetanurans (like carnosaurs and spinosaurids) had four fingers where known (coelophysoids, Dilophosaurus, Ceratosaurus, Carnotaurus, Xuanhanosaurus, Sinraptor, "Szechuanosaurus" zigongensis), except for Allosaurus, which had three.
As for Jonathan's original question, the only carnivorous dinosaur with a large dorsal sail is Spinosaurus. Modern research indicates this "sail" may have been a hump instead. This species was actually quite large, reaching lengths of fifty feet or so (as recently discussed on this list). It lived about 120-90 million years ago in the Cretaceous period in Egypt, Kenya, Morocco and Tunisia. It was originally found in 1915 and described by German paleontologist Ernst Stromer. The remains (consisting of a lower jaw, vertebrae and ribs) were later destroyed in World War II. Since then, more jaw remains, teeth and vertebrae have been discovered. Most of what we know about Spinosaurus comes from its relatives Baryonyx and Suchomimus, which are known from more complete skeletons. These three dinosaurs are all in the same family, the Spinosauridae.