''Lytoceras'' is an

ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...

genus that was extant during most of the Jurassic and Cretaceous periods, and is the type genus for the family

Lytoceratidae Lytoceratidae is a taxonomic family of ammonoid cephalopods belonging to the suborder Lytoceratina, characterized by very evolute shells that generally enlarge rapidly, having whorls in contact but mostly overlapping very sightly, or not at all. ...

. These cephalopods were fast-moving nektonic carnivores.

Description

Shells of ''Lytoceras'' are evolute, round or quadrate in section, covered with crinkled growth lines or riblets, and may have slight constrictions on internal molds. Some have fine striations, (parallel grooves running longitudinally along the flanks).

Distribution

Fossils of species within this genus have been found in the

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 Mya. The J ...

and

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

rocks all over the world, particularly in Western Europe, Morocco, Madagascar, South Africa and United States.

References

*Systematic descriptions, Mesozoic Ammonoidea, by W.J Arkell, Bernhard Kummel, and C.W. Wright. 1957. Treatise on Invertebrate Paleontology, Part L. Geological Society of America and University of Kansas press. Jurassic ammonites Cretaceous ammonites Ammonites of Europe Sinemurian genus first appearances Pliensbachian genera Toarcian genera Aalenian genera Bajocian genera Bathonian genera Callovian genera Oxfordian genera Kimmeridgian genera Tithonian genera Berriasian genera Valanginian genera Hauterivian genera Barremian genera Aptian genera Albian genera Cenomanian genus extinctions Ammonites of Asia Ammonitida genera Lytoceratidae {{ammonitida-stub