Ancyloceratida Fossil range: Jurassic - Cretaceous
A reconstruction of an heteromorph ammonite, Hamites sp
Scientific classification
Kingdom: Animalia Phylum: Mollusca Class: Cephalopoda Subclass: Ammonoidea Order: Ammonitida Suborder: Ancyloceratina Wiedmann, 1966
Superfamilies
See text Ancylocerataceae Douvilleicerataceae Turrilitaceae Deshayesitaceae Scaphitaceae

The Ancyloceratina were a diverse suborder of ammonite most closely related to the ammonites of order Lytoceratina. The Jurassic is a geologic period and system that extends from about Ma (million years ago to  Ma that is from the end of the Triassic to the beginning The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of Hamites ("Hook-stone" is a Genus of heteromorph Ammonite that evolved late in the Aptian stage of the Early Cretaceous Molluscs are animals belonging to the phylum Mollusca. There are around 250000 extant Species within the phylum with an estimated 70000 The cephalopods ( Greek plural (kephalópoda "head-feet" are the Mollusc class Cephalopoda characterized by Ammonites are an extinct group of marine animals of the subclass Ammonoidea in the class Cephalopoda phylum Ammonites are an extinct group of marine animals of the subclass Ammonoidea in the class Cephalopoda phylum In Biological classification, family ( Latin Classification of Ancyloceratida Superfamily Turrilitaceae ("Tower Stones" was a superfamily of heteromorph Ammonites of the suborder Ancyloceratina that lived during the Cretaceous Ammonites are an extinct group of marine animals of the subclass Ammonoidea in the class Cephalopoda phylum Lytoceratina is a Suborder belonging to the extinct Cephalopod subclass Ammonoidea. They evolved during the Late Jurassic but were not very common until the Cretaceous period, when they rapidly diversified and become one of the most distinctive components of Cretaceous marine faunas. The Jurassic is a geologic period and system that extends from about Ma (million years ago to  Ma that is from the end of the Triassic to the beginning The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of They have been recorded from every continent and many are used as zonal or index fossils. Index fossils (also known as guide fossils or zone fossils are Fossils used to define and identify geologic periods (or faunal stages The most distinctive feature of the majority of the Ancyloceratina is the tendency for most of them to have shells that are not regular spirals like most other ammonites. These irregularly-coiled ammonites are called heteromorph ammonites, in contrast to regularly-coiled ammonites, which are called homomorph ammonites.

A ammonite of the genus Hoploscaphites from South Dakota. Much of the original nacre shell is still present. Nacre, also known as mother of pearl, is an organic-inorganic Composite material produced by some Mollusks as an inner shell layer

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. In Physics, buoyancy ( BrE IPA: /ˈbɔɪənsi/ is the upward Force on an object produced by the surrounding liquid or gas in which it is Examples of such types were Ancyloceras, Protanisoceras, and Tropaeum. Ancyloceras is an extinct Genus of Heteromorph Ammonite Cephalopod found throughout the world during the Cretaceous Tropaeum ("Trophy" is an extinct Genus of Ammonite Cephalopod found throughout the oceans of the world during the Early 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. Hamites ("Hook-stone" is a Genus of heteromorph Ammonite that evolved late in the Aptian stage of the Early Cretaceous A paper clip (or sometimes paperclip) is a device which holds several sheets of Paper together by means of Pressure: it leaves the paper intact and

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. Baculites ("walking stick rock" is a Genus of extinct marine animals in the Phylum Mollusca and Class Nipponites ("Stone of Nippon " is an extinct Genus of Heteromorph Ammonites The species of Nipponites (primarily 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.

Not all the Ancyloceratina had such strangely shaped shells; 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. Scaphites ( Greek skafh, "a boat or anything dug or scooped out" is a Genus of extinct Cephalopod belonging to the

Scaphites sp. - specimen is 2. 8 cm top to bottom

The biology of the heteromorph ammonites is not clear, but one certainty is that their uncoiled shells would have made these forms very poor swimmers. Open shells, particularly ones with spines and ribs, create a lot of drag; but more importantly, the orientation of the shell, with the body hanging below the buoyant part of the shell, would have created a serious impediment to efficient swimming. It's more likely these ammonites either drifted in the plankton, collecting small animals on long tentacles like modern jellyfish, or else they crawled along the sea floor feeding on sessile or slow-moving animals such as clams. Plankton consist of any drifting Organisms ( Animals Plants Archaea, or Bacteria) that inhabit the Pelagic zone of Tentacles can refer to the elongated flexible organs that are present in some animals especially Invertebrates and sometimes to the hairs of the leaves of some insectivorous Jellyfish are free-swimming members of the phylum Cnidaria. They have several different basic morphologies that represent several different cnidarian classes including the Clam is a word which can be used for all some or only a few Species of Bivalve Mollusks the word is a Common name which has

Ancyloceratida varied widely in size, ranging from diminutive Ptychoceras, which was barely 3 cm long, to Baculites and Diplomoceras, which could grow to 1-2 m in length. Some species were very widely distributed, for example some species of Hamites can be found in Eurasia, South America, Australia, and Antarctica. For the superstate in George Orwell 's novel see Nations of Nineteen Eighty-Four. South America is a Continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a For a topic outline on this subject see List of basic Australia topics. Others, like those inhabiting the Western Interior Seaway that covered much of the US, were much more localized. The Western Interior Seaway, also called the Cretaceous Seaway, the Niobraran Sea, and the North American Inland Sea, was a huge inland Sea

See also

• Nautiloid
• Lituites
• Orthoceras

External links

• Scientific report on the functional morphology of Cretaceous heteromorph ammonites