Ammonoceratites is an extinct genus of ammonoid cephalopod known from the Albian of British Columbia, Madagascar, New Zealand, and Japan, included in the Lytoceratidae.
Astiericeras is an ammonite from the Lower Cretaceous, the shell of which is evolute, stout; outer whorl with strong, well spaced, transverse ribs that cross smoothly over the broad venter; early whorls with lateral tubercles. The outer, mature whorl separates from the coil but hooks back quickly, referred to as a heteromorph.
Astieridiscus is an extinct lower Cretaceous ammonite. Its shell evolute, covered by dense, simple or branching, slightly flexuous ribs. The sides are slightly flattened, the venter rounded. No umbilical or other tubercles except on innermost whorl. Superficially resembles Olcostephanus.
Barremites is an ammonoid cephalopod belonging to the family Desmoceratidae, that lived during the Hauterivian and Barremian stages of the Early Cretaceous. Its shell is moderately to very involute, with the outer whorl strongly embracing the inner whorls, and variably compressed. Sides are generally smooth and marked with sinuous or falcate collars marking intervals of growth and bearing feeble striae to moderately distinguished ribs.
Desmoceratidae is a family belonging to the ammonite superfamily Desmoceratoidea. They are an extinct group of ammonoids, shelled cephalopods related to squid, belemnites, octopuses, and cuttlefish, and more distantly to the nautiloids, that lived between the Lower Cretaceous and Upper Cretaceous.
Ammonitina comprises a diverse suborder of ammonite cephalopods that lived during the Jurassic and Cretaceous periods of the Mesozoic Era. They are excellent index fossils, and it is often possible to link the rock layer in which they are found to specific geological time periods.
Nipponites is an extinct genus of heteromorph ammonites. The shells of Nipponites form "ox-bow" bends, resulting in some of the most bizarre shapes seen among ammonites.
Bostrychoceras is a genus of heteromorph ammonite from the family Nostoceratidae. Fossils have been found in Late Cretaceous sediments in Europe and North America.
Hoploscaphites is an extinct ammonite genus from the Upper Cretaceous, included in the family Scaphitidae.
Zetoceras is an extinct ammonoid cephalopod genus from the suborder Phylloceratina that lived during the Early and Middle Jurassic in what is now Europe, and is included in the (family) Phylloceratidae.
Perisphinctoidea, formerly Perisphinctaceae, is a superfamily of Middle Jurassic (Bajocian) to Lower Cretaceous (Barremian) ammonites, commonly with evolute shells with strong ribbing that typically divides about mid flank before crossing the venter.
Desmoceratoidea, formerly Desmocerataceae, is a superfamily of Cretaceous ammonites, generally with round or oval-whorled shells that are mostly smooth or weakly ribbed and rarely tuberculate, but commonly with constrictions. Regarded as monophyletic, the Desmocerataceae are derived from the Phylloceratidae, splitting off in the Early Cretaceous (Valanginian) and persisting to the end of the Maastrichtian.
Lytocrioceras is a genus of ancyloceratine ammonites from the Lower Cretaceous with a shell that resembles a safety pin. The shell begins as a loosely wound spiral, followed by a straight shaft which makes a U-turn to go back is somewhat the opposite direction, ending in a jog, offset from the original coil.
Ancyloceratidae is a family of heteromorphic ammonites that lived during the Early Cretaceous. Their shells begin as a loose spiral with whorls not touching which then turns into a straight shaft that ends in a J-shape hook or bend at end. Coarse ribbing and spines are common.
Hypophylloceras is a Cretaceous ammonite with a finely ribbed, compressed, involute shell; some having periodic stronger ribs or folds. The suture is complex, with large, asymmetric and finely divided lobes; the 1st lateral being much larger than the external (=ventral) and 2nd lateral lobes. Saddle endings commonly not phylloid.
Lytoceras is an ammonite genus that was extant during most of the Jurassic and Cretaceous periods, and is the type genus for the family Lytoceratidae. These cephalopods were fast-moving nektonic carnivores.
Neocomitidae is a family of Lower Cretaceous ammonitids comprising genera with strongly ribbed evolute to smooth, fairly involute shells.
Melchiorites is a desmoceratid ammonite genus included in the subfamily Puzosiinae. Member species are characterized by an essentially evolute shell in which the early whorls are smooth, with sinuous radial or oblique constrictions but in which later whorls have feeble intermediate ribs on the outer part of the sides and venter.
The Acanthoceratinae comprise a subfamily of ammonoid cephalopods that lived during the Late Cretaceous from the latter early Cenomanian to the late Turonian
Euomphaloceras is an early Upper Cretaceous ammonite genus,, included in the Acanthoceratinae until established as the type genus for the Euomphaloceratinae by Cooper, 1978.
