Perisphinctes

Perisphinctes – ammonite. The exhibit from the Museum of Natural History in Berlin

Perisphinctes is an extinct genus of ammonite cephalopod. They lived during the Jurassic Period and serve as an index fossil for that time period.

The Perisphinctes boweni ammonite was named after the English chemist and geologist E. J. Bowen (1898–1980).

Description

The appearance of the shell of this ammonite is quite conventional: planispirale (wrapped in a flat spiral), symmetrical, serpenticona (shaped like a coiled snake, with little overlap of the turns).

At each stage of growth, the shell has a section sub-square with rounded corners; the navel is very broad but shallow. The ornamentation consists of many coasts angular and slightly proverse (arched forward, i.e. in the direction of the opening). Near the belly, the coasts forking, crossing the ventral region seamless (there are no hulls or ventral furrows). In certain species, in the mature stage (and in general in macroconche) simplifies the ornamentation and the coast can become more sparse, simple and rounded. In juvenile forms are present constraints (bottlenecks) irregular along the spiral of the shell. The suture line (ie the line of insertion of the baffles on the wall of the shell) is of type ammonitico, rather complex, with many elements little but very jagged. The diameter of the shell of the adult forms is on average about 7 centimeters (may vary depending on the species), although specimens are found to more than 20 centimeters.

One of the most known species was Perisphinctes plicatilis.

Habitat

It is thought that Perisphinctes lived in shallow water, in the inner part of the continental shelf and shelf seas interior, like all forms of the same family ( Perisphinctidae ). This ammonite was a form cosmopolitan, widespread in warm-temperate waters worldwide.

Scientific classification

  • Domain: Eukaryota – Whittaker & Margulis,1978 – eukaryotes
  • Kingdom: Animalia – C. Linnaeus, 1758 – animals
  • Subkingdom: Bilateria – (Hatschek, 1888) Cavalier-Smith, 1983
  • Branch: Protostomia – Grobben, 1908
  • Superphylum: Eutrochozoa
  • Phylum: Mollusca – (C. Linnaeus, 1758) Cuvier, 1795 – Molluscs
  • Class: Cephalopoda – Cuvier, 1797 – Cephalopods
  • Subclass: Ammonoidea
  • Order: Ammonoidea
  • Superfamily: Perisphinctaceae
  • Family: Perisphinctidae
  • Genus: Perisphinctes  – Waagen, 1869
  • Specific name: promiscuus
  • Scientific name:  Perisphinctes promiscuus

Photos

Specimen of Perisphinctes (Prosososphinctes) virguloides (Waagen) from Madagascar. Credit: Antonov
Perisphinctes cf P. choffati Credit: Ghedoghedo
Museo di Storia Naturale di Verona Credit: Ghedoghedo
Perisphingtes oxfordien Credit: Bildoj

Reference:
Wikipedia(en) : Perisphinctes
Wikipedia (it) : Perisphinctes
Zipcode Zoo : Taxonomy

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