''Tropaeum'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

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 cuttlefis ...

s found throughout the oceans of the world during the Early

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 ...

. As with many other members of the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Ancyloceratidae Ancyloceratidae is a family of heteromorphic ammonites that lived during the Early Cretaceous. Their shells begin as a loose spiral with whorls not touching which then turns into a straight shaft that ends in a J-shape hook or bend at end. Coar ...

, there was a trend among species within this genus to uncoil somewhat, in a very similar manner to the genus ''

Lytoceras ''Lytoceras'' is an ammonite genus that was extant during most of the Jurassic and Cretaceous periods, and is the type genus for the family Lytoceratidae. These cephalopods were fast-moving nektonic carnivores. Description Shells of ''Lytoceras ...

''. The largest species, ''T. imperator'' of

Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...

, had a shell a little over one meter in diameter. The name "Tropaeum" was applied by paleontologist

James De Carle Sowerby James De Carle Sowerby (5 June 1787 – 26 August 1871) was a British mineralogist, botanist, and illustrator. He received an education in chemistry. Sowerby was born in London, the son of botanical artist James Sowerby (1757–1822), and his ...

, in 1837.

References

External links

* photograph of the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...

of ''T. imperator'

Ammonitida genera Early Cretaceous ammonites Ammonites of Australia Ancyloceratoidea {{Ammonite-stub