Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Protostomia
Cladus: Spiralia
Cladus: Lophotrochozoa
Phylum: Mollusca
Classis: Cephalopoda
Subclassis: †Ammonoidea
SubOrdo: Lytoceratina
Superfamilia: Tetragonitaceae
Name
Lytoceratina Hyatt 1889
References
Kennedy, W. J., Landman, N. H., Cobban, W. A., & Johnson, R. O., (2000). "Additions to the Ammonite Fauna of the Upper Cretaceous Navesink Formation of New Jersey" American Museum Novitates 3306(1):1–30
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 evolute, with all whorls exposed and touching, some are gyroconic with whorls separated by a space. Whorl sections vary from subcircular to narrowly compressed. The venter, or outer rim, is generally broadly arched but in some is keeled. Sides are either smooth or ribbed. Sutural elements are typically complex, referred to in the literature as moss-like, with adventious and secondary subdivisions. Saddle endings tend to be rounded but usually not phylloid, lobes tend to be more jagged with thorn-like endings. Aptychi are single valved and concentrically striated (Anaptychus)
Derivation and phylogeny
The Lytoceratina, which constitute a suborder within the Ammonitida, are derived from the Triassic Ussuritidae or Discophyllitidae, families belonging to the Phylloceratina, or both (which would make them polyphyletic). They in turn gave rise to the main body of Jurassic Ammonitina and to the Cretaceous Ancyloceratina.
Included Families
Twelve families have been described of which the Lytoceratidae dominate. The Lytoceratidae also have the longest range, from the Lower Jurassic to the Cenomanian stage in the Upper Cretaceous.
References
Arkell et al., Mesozoic Ammonoidea, Treatise on Invertebrate Paleontology, Part L, Mollusca 4; Geol Soc of America & Univ. Kansas press, 1957.
The Paleobiology Database - Lytoceratina 4/05/10
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