suborder
Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized ...
of
ammonoid
Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...
cephalopods, belonging to the
Ammonitida
Ammonitida, or true ammonites, are an order of Ammonoidea, ammonoid cephalopods that lived from the Jurassic through Paleocene time periods, commonly with intricate ammonitic sutures.
Ammonitida is divided into four suborders, the Phylloceratina ...
, whose range extends from the Lower
Triassic
The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...
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 ...
. Shells of the Phylloceratina are generally smooth with small to large umbilici and complex sutures with leaf-like phylloid saddle endings and lobes with thornlike projections.
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
Phylogeny
The Phylloceratina are most likely derived from the
Ceratitid
Ceratitida is an order that contains almost all ammonoid cephalopod genera from the Triassic as well as ancestral forms from the Upper Permian, the exception being the phylloceratids which gave rise to the great diversity of post-Triassic ammon ...
Deineroceratidae, which is thought to have given rise early in the Triassic to the Ussuritidae. The Ussuritidae is the ancestral family of the Phylloceratina. The Ussuritidae extend through the Upper Triassic but not into the Jurassic, and gave rise to the Upper Triassic Discophyllitidae. The Discophyllitidae is the probable source for the L Jurassic - U Cretaceous Phylloceratidae and possibly for the L Jurassic Juraphyllitidae.
The Phylloceratina gave rise early in the Jurassic through the Phylloceratidae to the Lytoceratina, which in turn gave rise to most of the Ammonitina The Phylloceratidae also gave rise 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 ...