Nostoceratidae
Encyclopedia
Family
Nostoceratidae was a diverse group of heteromorph ammonite
s found throughout the oceans of the world during the Late Cretaceous
. The nostoceratids are famous for the bizarre coiling of their shells. Many genera, such as Yezoceras, Ainoceras
, Anaklinoceras
, and some species of Bostrychoceras
and Eubostrychoceras
, display, as young shells at least, a helical coiling very similar to the shells of the related family, Turrilitidae
. As adults, though, the coils then curve away from the axis of coiling, either as an oxbow
-like curve around the juvenile coils as in Ainoceras and Anaklinoceras, or in a simple curved loop beneath the juvenile coils, as in Yezoceras. Other genera form loose coils, sometimes in a spiral, such as those of Madagacarites (Ryuella), Muramotoceras
, Hyphantoceras, and the infamous Nipponites
.
The ecology of nostoceratids is the subject of continued speculation, as the bizarrely coiled shells have no streamlining, strongly suggesting that the living animals had extraordinarily poor swimming ability, if any ability at all. As such, experts and ammonite enthusiasts presume that the nostoceratids either floated passively in the water column, or were bottom-dwellers that may or may not have crawled on the seafloor.
The nostoceratids, as with all other Cretaceous ammonites, perished during the Cretaceous–Tertiary extinction event.
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Nostoceratidae was a diverse group of heteromorph ammonite
Ammonite
Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct subclass within the Molluscan class Cephalopoda which are more closely related to living coleoids Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct...
s found throughout the oceans of the world during the Late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
. The nostoceratids are famous for the bizarre coiling of their shells. Many genera, such as Yezoceras, Ainoceras
Ainoceras
Ainoceras is a genus of extinct, aberrantly coiled ammonite cephalopod that live in the Pacific Ocean during the Campanian division of the Cretaceous, where Japan is today...
, Anaklinoceras
Anaklinoceras
Anaklinoceras is a genus of extinct heteromorph ammonite cephalopod that lived in marine environments in what is now Western North America during the Campanian division of the Cretaceous period...
, and some species of Bostrychoceras
Bostrychoceras
Bostrychoceras is a genus of ammonite from the Late Cretaceous. Its fossils have been found in Europe and North America.- Sources :* Ammonoid Paleobiology by Neil H. Landman, Kazushige Tanabe, and Richard Arnold Davis...
and Eubostrychoceras
Eubostrychoceras
Eubostrychoceras is a genus of helically wound, corkscew form, heteromorph ammonite which lived during the Upper Cretaceous . The genus is included in the ancycleratid family Nostoceratidae....
, display, as young shells at least, a helical coiling very similar to the shells of the related family, Turrilitidae
Turrilitidae
Turrilitidae is a family of extinct heteromorph ammonite cephalopods. All members had shells that coiled helically that tended to resemble auger shells....
. As adults, though, the coils then curve away from the axis of coiling, either as an oxbow
Oxbow
An oxbow is a U-shaped wooden or metal frame that fits under and around the neck of an ox or bullock, with its upper ends passing through the bar of the yoke and held in place with a metal key, called a bow pin. The wood most often used is hardwood steamed into shape, like elm or hickory and...
-like curve around the juvenile coils as in Ainoceras and Anaklinoceras, or in a simple curved loop beneath the juvenile coils, as in Yezoceras. Other genera form loose coils, sometimes in a spiral, such as those of Madagacarites (Ryuella), Muramotoceras
Muramotoceras
Muramotoceras was an unusual genus of heteromorphic ammonite. It was known only from Japan until researchers reported in 2001 that the genus was present in Alaska's Matanuska Formation as well. Its remains likely date to the middle Turonian in both areas....
, Hyphantoceras, and the infamous Nipponites
Nipponites
Nipponites is an extinct genus of heteromorph ammonites. The species of Nipponites are famous for the way their shells form "ox-bow" bends, resulting in some of the most bizarre shapes ever seen among ammonites.The ecology of Nipponites, as with many other nostoceratids, is subject to much...
.
The ecology of nostoceratids is the subject of continued speculation, as the bizarrely coiled shells have no streamlining, strongly suggesting that the living animals had extraordinarily poor swimming ability, if any ability at all. As such, experts and ammonite enthusiasts presume that the nostoceratids either floated passively in the water column, or were bottom-dwellers that may or may not have crawled on the seafloor.
The nostoceratids, as with all other Cretaceous ammonites, perished during the Cretaceous–Tertiary extinction event.