| Polyptychoceras Temporal range: Late Cretaceous | |
|---|---|
 | |
| Subptychoceras yubarense | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Subclass: | † Ammonoidea |
| Order: | † Ammonitida |
| Suborder: | † Ancyloceratina |
| Family: | † Diplomoceratidae |
| Genus: | † Polyptychoceras Yabe, 1927 [1] |
| Species | |
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Polyptychoceras is an extinct genus of ammonites from the Late Cretaceous of Asia, Europe, and North [2] and South America. It was first named by Hisakatsu Yabe in 1927. [3]
This genus contains the following eight species and one subgenus, Subtychoceras, which contains one species. [3]
Polyptychoceras is a heteromorph ammonite, meaning that its shell does not curl up into the tight spiral shape which shells of ammonites from the subclass Ammonoidea typically do.
Polyptychoceras shells have an abrupt weight increase after formation of the initial shaft, which represents the shell's automatic balance condition. [4] This would have caused the shell to topple over if on land. [4] The soft body of the animal would have to have been large, in order to keep the falling shaft off of the ground. [4] The body would not have been resistant to the pressing shell. [4]
Although the shafts in the fossils of the shells are usually parallel to each other, small aberrations during each growth stage often caused abrupt constrictions in the shape of the shell. [5]
A Japanese study in 1979 suggested that Polyptychoceras lived and travelled in schools, similarly to modern cuttlefish. [3] Individual fossil specimens of a particular species of Polyptychoceras are frequently found in sediments laid down in the same bed of water, around the Santonian and Upper Coniacian faunal stages of the Late Cretaceous Epoch. [3] Polyptychoceras was probably buoyant, and swam in a slow, somewhat up-and-down locomotion. [3] It also likely preferred living in sheltered parts of deep sea levels, although how deep is uncertain. [3] Subptychoceras yubarense was likely very long like an eel, [3] and preferred a benthic mode of life. [3]
Fossils of Polyptychoceras have been found in Angola, Antarctica, Argentina, Austria, Japan, Mexico, the Russian Federation, and the United States (California). [6]
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 than they are to shelled nautiloids such as the living Nautilus species. The earliest ammonites appeared during the Devonian, and the last species either vanished in the Cretaceous–Paleogene extinction event, or shortly after during the Danian epoch of the Paleocene.
Hamites is a genus of heteromorph ammonite that evolved late in the Aptian stage of the Early Cretaceous and lasted into the Cenomanian stage of the Late Cretaceous. The genus is almost certainly paraphyletic but remains in wide use as a "catch all" for heteromorph ammonites of the superfamily Turrilitoidea that do not neatly fit into the more derived groupings. In an attempt to identify clades within the genus, it has been divided up into a series of new genera or subgenera by different palaeontologists, including Eohamites, Hamitella, Helicohamites, Lytohamites, Planohamites, Psilohamites, and Sziveshamites.
Baculites is an extinct genus of cephalopods with a nearly straight shell, included in the heteromorph ammonites. The genus, which lived worldwide throughout most of the Late Cretaceous, and which briefly survived the K-Pg mass extinction event, was named by Lamarck in 1799.
The Ancyloceratina were a diverse suborder of ammonite most closely related to the ammonites of order Lytoceratina. They evolved during the Late Jurassic but were not very common until the Cretaceous period, when they rapidly diversified and became one of the most distinctive components of Cretaceous marine faunas. They have been recorded from every continent and many are used as zonal or index fossils. The most distinctive feature of the majority of the Ancyloceratina is the tendency for most of them to have shells that are not regular spirals like most other ammonites. These irregularly-coiled ammonites are called heteromorph ammonites, in contrast to regularly coiled ammonites, which are called homomorph ammonites.
Scaphites is a genus of heteromorph ammonites belonging to the Scaphitidae family. They were a widespread genus that thrived during the Late Cretaceous period.
Inoceramus is an extinct genus of fossil marine pteriomorphian bivalves that superficially resembled the related winged pearly oysters of the extant genus Pteria. They lived from the Early Jurassic to latest Cretaceous.
Ancyloceras is an extinct genus of heteromorph ammonites found throughout the world during the Lower Cretaceous, from the Lower Barremian epoch until the genus extinction during the Lower Aptian.
Astreptoceras is an extinct upper Cretaceous ammonoid cephalopod named by Henderson in 1970. Fossils belonging to this genera have been found in Antarctica and New Zealand.
Urakawites is an extinct Ammonite from the Upper Cretaceous (Campanian) of Japan, Sakhalin, Russia, British Columbia, Canada and possibly Germany and Angola. Urakawites is placed in the family is Pachydiscidae.
Anisoceratidae is an extinct family of heteromorph ammonites which belong to the Ancyloceratina superfamily Turrilitoidea. Members of the family range is from the lower Albian to the upper Turonian. The family is possibly derived from a member of the Hamitidae.
Nipponites is an extinct genus of heteromorph ammonites. The shells of Nipponites form "ox-bow" bends, resulting in some of the most bizarre shapes seen among ammonites.
Exiteloceras is an ammonite genus from the Late Cretaceous.
Heteroceras is a Lower Cretaceous heteromorph ammonite belonging to the ancyloceratacian family, Heteroceratidae, characterized by a helically coiled juvenile shell at the apex followed by slightly curved adult shaft, with a J-shaped section at the end of it. The shell is ribbed; ribs are concave and oblique on the helix, straight and transverse on the later stages.
Eubostrychoceras is a genus of helically wound, corkscrew form, heteromorph ammonite which lived during the Upper Cretaceous. The genus is included in the ancycleratid family Nostoceratidae.
Macroscaphites is an extinct cephalopod genus included in the Ammonoidea that lived during the Barremian and Aptian stages of the Early Cretaceous. Its fossils have been found throughout most of Europe and North Africa.
Paleontology in Alaska refers to paleontological research occurring within or conducted by people from the U.S. state of Alaska. During the Late Precambrian, Alaska was covered by a shallow sea that was home to stromatolite-forming bacteria. Alaska remained submerged into the Paleozoic era and the sea came to be home to creatures including ammonites, brachiopods, and reef-forming corals. An island chain formed in the eastern part of the state. Alaska remained covered in seawater during the Triassic and Jurassic. Local wildlife included ammonites, belemnites, bony fish and ichthyosaurs. Alaska was a more terrestrial environment during the Cretaceous, with a rich flora and dinosaur fauna.
Cephalopod egg fossils are the fossilized remains of eggs laid by cephalopods. The fossil record of cephalopod eggs is scant since their soft, gelatinous eggs decompose quickly and have little chance to fossilize. Eggs laid by ammonoids are the best known and only a few putative examples of these have been discovered. The best preserved of these were discovered in the Jurassic Kimmeridge Clay of England. Currently no belemnoid egg fossils have ever been discovered although this may be because scientists have not properly searched for them rather than an actual absence from the fossil record.
Scalarites is a genus of heteromorph ammonites included in the family Diplomoceratidae. These fast-moving nektonic carnivores lived in the Cretaceous period, from 89.3 to 70.6 million years ago). These fossils have been found in Antarctica, Brazil, Denmark, Germany, Japan, Russia, Sweden and United States.
Diplomoceratidae is a family of ammonites included in the order Ammonitida. Fossils of species within this genus have been found in the Cretaceous sediments. Studies of Diplomoceras suggest that members of this family could reach lifespans of over 200 years.
Antarcticoceras is a genus of crioconic ammonites in the family Shasticrioceratidae. It lived during the Early Cretaceous Period. Antarcticioceras fossils can be found in the Cretaceous rocks of Antarctica and South America.