Gaudryceratidae

Belongs within: Lytoceratida. The Gaudryceratidae are a lineage of ammonites known from the Barremian to the Maastrichtian of the Cretaceous (Wright et al. 1996). Characters (from Wright et al. 1996): Whorl section typically rounded or elliptical, sometimes depressed; shell ornamented with lirae or fine riblets, occasionally smooth, and with constrictions; suture with symmetrically bifid saddles… Continue reading Gaudryceratidae

Tetragonitidae

Belongs within: Lytoceratida. The Tetragonitidae are a lineage of lytoceratidan ammonites known from the Upper Aptian to the Maastrichtian of the Cretaceous (Wright et al. 1996). Characters (from Wright et al. 1996): Whorl section rectangular or trapezoidal in early whorls, sometimes depressed; usually smooth, occasionally lirate or striate; constrictions on internal mold strongly prorsiradiate but… Continue reading Tetragonitidae

Lytoceratida

Belongs within: Neoammonoidea.Contains: Tetragonitidae, Gaudryceratidae, Crioceratites. The Lytoceratida are a lineage of ammonites known from the Jurassic and Cretaceous. Their sutures are characterised by denticulated saddles with bipolar frilling (Wiedmann & Kullmann 1981). Characters (from Engeser & Keupp 2002): Conch thin-walled, usually weakly sculptured. Suture line with primary sutural formula ELU2U1I; suture elements microphyll (strongly… Continue reading Lytoceratida

Phylloceratidae

Belongs within: Neoammonoidea. The Phylloceratidae are a group of ammonites with mostly smooth or feebly ornamented conchs, and phylloid saddle endings of the suture line (Engeser & Keupp 2002). They have a long stratigraphic range from the early Jurassic to the end of the Cretaceous. Phylloceratidae |–Phyllopachyceras Spath 1925 [Phyllopachyceratinae]DJ95 | |–*P. infundibulum (d’Orbigny 1841)… Continue reading Phylloceratidae

Ammonoidea

Belongs within: Cephalopoda.Contains: Parabactritidae, Coleoidea, Bactrites, Agoniatitina. The Ammonoidea sensu stricto are a highly diverse group of shelled cephalopods known from the Devonian to the Cretaceous. Most forms had coiled shells though some had straight or irregular conches. The siphuncle usually has a ventral position. Early forms had simple sutures, but sutures in later forms… Continue reading Ammonoidea

Ammonitida

Belongs within: Neoammonoidea.Contains: Ammonites, Arietitinae, Oxynoticeratidae, Eoderoceratidae, Polymorphitidae, Aptychophora, Dactylioceratidae. The Ammonitida (here used for the Ammonitina of some authors) are a group of ammonoids known from the Jurassic and Cretaceous with five-lobed primary sutures. Early members of this lineage retained a single hemispherical anaptychus with which to close the body chamber; this became divided into… Continue reading Ammonitida

Crioceratites

Belongs within: Lytoceratida. Crioceratites is a genus of ammonites with a tendency to become openly coiled, known from the Upper Valanginian to the Upper Barremian of the Lower Cretaceous (Wright et al. 1996). Characters (from Wright et al. 1996): Typically coiled in equiangular spiral, but spiral angle may increase with age; whorl section oval to… Continue reading Crioceratites

Douvilleiceratidae

Belongs within: Stephanocerataceae. The Douvilleiceratidae are evolute ammonites known from the Barremian to the Middle Albian of the Lower Cretaceous (Wright et al. 1996). Characters (from Wright et al. 1996): Evolute; whorl section ranging from depressed to circular or polygonal; ribs strong, with various combinations of umbilical, lateral, or ventrolateral tubercles. Suture with massive saddle… Continue reading Douvilleiceratidae

Aptychophora

Belongs within: Ammonitida.Contains: Grammoceratinae, Spiroceratidae, Phymatoceratidae, Hammatoceratidae, Graphoceratidae, Sonniniidae, Stephanocerataceae, Oppeliidae, Strigoceratidae. The Aptychophora are a clade within the ammonites characterised by the development of bivalved aptychi, calcified lower jaws that probably functioned as opercula to close the entrance of the shell. Such structures are first known from the lower Toarcian (in the lower Jurassic)… Continue reading Aptychophora

Perisphinctoidea

Belongs within: Stephanocerataceae.Contains: Tulitidae, Perisphinctidae, Morphoceratidae, Neocomitidae. The Perisphinctoidea are a group of ammonoids known from the middle Jurassic to the early Cretaceous, many of which exhibit evolute, planulate conches with sharp, branched ribs (Énay & Howarth 2019). The perisphinctoids are thought to include the ancestors of most later Cretaceous Ammonitida, except those included in… Continue reading Perisphinctoidea