heteromorph ammonites from southeastern France Ancyloceratida varied widely in size, ranging from diminutive
Ptychoceras, which was barely long, to
Baculites and
Diplomoceras, which could grow to in length. Some species were very widely distributed, for example some species of
Hamites can be found in
Eurasia,
South America,
Australia, and
Antarctica. Others, like those inhabiting the
Western Interior Seaway that covered much of the US, were much more localized. In the more primitive forms, the shell departs only slightly from being a perfect spiral, with only the last, outermost whorl being open, forming a hook underneath the main spiral. In such forms the spiral was the chambered,
buoyant part of the shell, and the hook was the living chamber in which the soft body of the ammonite resided. Examples of such types were
Ancyloceras,
Protanisoceras, and
Tropaeum. The more advanced heteromorphs departed from such forms radically. The shells of
Ptychoceras consisted of three or four shafts squashed together and connected with tight, 180 degree bends. Members of the genus
Hamites were much larger but had a similar sort of shape, though the shafts were open so that the whole thing looked rather like a big
paper clip. Many of the earlier heteromorph forms had regularly coiled shells barely distinguishable from the homomorph ammonites (for example, the Lower Cretaceous genus
Deshayesites). Some offshoots of the uncoiled varieties even went back to being regularly coiled. Most notable among these were the
Scaphites,
Hoploscaphites and their relatives, which were mostly regular spirals in shape except for a very slight hook at the end. The Late Cretaceous enjoyed the widest variety of heteromorphs, including the straight-shelled
Baculites and
Sciponoceras; the helically coiled
Turrilites; and the bizarre
Nipponites, which looked more like a ball of string than anything else. Some forms combined different coiling modes. For example,
Nostoceras started off with a helix like a
Turrilites, but had a planar hook hanging underneath, more like an
Ancyloceras. The thin shelled heteromorphic ammonites probably lived at depths . ==Classification==