Dinosaurs was a LEGO theme released in 2001. This theme included different kinds of dinosaur models, in adult for as well as smaller younger forms. This theme did not include any normal minifigures. This theme is the origin of the building style for many animals released later on such as the dewback in 4501 Mos Eisley Cantina from Star Wars.
The four larger sets (6719-6722) were packaged in plastic canisters. These canisters were black, and they had a cuboid form. They have the appearance of a block of stone, with "fossilized" bones being visible. The lid also serves as a stand for the built dinosaurs, even though it could be difficult to place them on it without them falling over.
Boxes and Polybags
The sets 5950 to 5953 and 7000 to 7003 are the smaller sets of the theme. They include baby/young versions of dinosaurs. Those sets are in fact the same, the only difference being 5950 - 5953 were packaged in Polybags, while 7000 - 7003 came in boxes.
The four main dinosaurs, packaged in canisters, include additional parts to rebuild the main dinosaur into another:
6719 Brachiosaurus can be rebuilt into a Diplodocus, Plateosaurus and a Plesiosaurus.
6720 Tyrannosaurus Rex can be rebuilt into an Ouranosaurus, Parasaurolophus and a Spinosaurus.
6721 Mosasaurus can be rebuilt into a Dimetrodon, Iguanodon and a Postosuchus.
6722 Styracosaurus can be rebuilt into a Camarasaurus, Centrosaurus and aTriceratops.
These are smaller sets in the theme that came in Boxes and Polybags , all released in 2001.