Phylloceratidae is the predominant family of the

Phylloceratina The Phylloceratina comprise a suborder (biology), suborder of Ammonoidea, ammonoid cephalopods, belonging to the Ammonitida, whose range extends from the Lower Triassic to the Upper Cretaceous. Shells of the Phylloceratina are generally smooth w ...

with some 15 or more genera found in rocks ranging from the Lower

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

to the Upper

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

. Members of the Phylloceratidae are characterized by smooth, involute shells with very thin walls. Many are covered with fine growth lines but are usually without ribbing. Sutures are complex with the major and minor branches of the saddles with phylloid or spatulate endings.

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authore ...

Part L Mollusca 4, Ammonoidea, 1957

Evolution and phylogeny

The Phylloceratidae are probably derived from the Late Triassic

Discophyllitidae Discophyllitidae are discoidal, generally evolute Phylloceratina from the Upper Triassic, derived from the Ussuritidae, in which the principal saddles of the suture have bifurcated or trifurcated endings, described as being di- or triphyllic. Di ...

by increasing the sutural complexity and evolving involute coiling. The Discophyllitidae in turn have their origin in the

Ussuritidae Ussuritidae are ancestral, Triassic, Phylloceratina characterized by generally smooth, discoidal, evolute shells with rounded venters and little or no ornamentation and by sutures with primitive monophyllitic saddles with a single terminal branch ...

, also known as the Monophyllitidae. The Phylloceratidae gave rise at or near the beginning of the Jurassic to the ancestral

Lytoceratina Lytoceratina is a suborder of Jurassic and Cretaceous ammonites that produced loosely coiled, evolute and gyroconic shells in which the sutural element are said to have complex moss-like endings. Morphologic characteristics Shells are generally ...

, the early Lower Jurassic Peluroacanthitidae and Ectocentridae. The Phyloceratidae also gave rise at or near the beginning of the Jurassic to the

Psiloceratoidea Psiloceratoidea is a superfamily of Early Jurassic Ammonoidea, ammonoid cephalopods proposed by Alpheus Hyatt, Hyatt in 1867, assigned to the order Ammonitida. They were very successful during Hettangian and Sinemurian. Last of them, family Cym ...

which unites families of the Early Jurassic

Ammonitina Ammonitina comprises a diverse suborder of Ammonoidea, 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 the ...

. Other Jurassic Ammonitina are derived from the Lytoceratina. Later, phylloceratids are said to have given rise to Cretaceous Ammonitina included in the

Desmoceratoidea 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.Hoplitoidea Hoplitoidea, formerly Hoplitaceae, is a superfamily of mostly Upper Cretaceous ammonites comprising families united by a similar suture pattern with multiple similar elements that tend to decrease in size going toward the umbi ...

, and

Acanthoceratoidea Acanthoceratoidea, formerly Acanthocerataceae, is a superfamily of Upper Cretaceous ammonoid cephalopods belonging to the order Ammonitida, and comprising some 10 or so families.W.J Arkell ''et al''., Mesozoic Ammonoidea; Treatise on Invertebrat ...

Sutural morphology

Sutures in the Phylloceratidae vary in complexity and are usually described on the basis of the saddles, which diverge to the front. Saddle endings may be double (diphyllic), triple (triphyllic), or quadruple (tetraphillic). Branching may be asymmetric. Intervening lobes are variably branched with thornlike or spinose terminations as viewed in plan.

Subfamilies and genera

* Calliphylloceratinae Spath, 1927 **'' Calliphylloceras'' Spath, 1927 **'' Holcophylloceras'' Spath, 1927 **'' Ptychophylloceras'' Spath, 1927 **'' Sowerbyceras'' Parona & Bonarelli, 1895 * Phylloceratinae Zittel, 1884 **'' Calaiceras'' **'' Carinophylloceras'' Klinger et al., 1975 **'' Hantkeniceras'' **'' Hypophylloceras'' (Salfeld, 1924) **'' Partschiceras'' Fucini, 1920 **'' Phylloceras'' Suess, 1865 **'' Phyllopachyceras'' Spath, 1925 **'' Zetoceras'' Kovacs, 1939 *''

incertae sedis or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...

'' **'' Bonarellia''

References

{{Taxonbar, from=Q7188670 Ammonitida families Early Jurassic first appearances Late Cretaceous extinctions