Orthoceras Fossil Nautiloid Sea Shell Prehistoric Devonian Collection (5)

Orthocerate Fossil Seashell mm 100 x 41 x 15 gr 83 Orthoceras regulare  Extinct Prehistoric Cephalopods Molluscs Paleozoic Devonian Collecting Paleontology Museum.
N.B. it is sometimes misspelled as Orthocera, Orthocerus or Orthoceros.

Pleasant collectible fossil specimen of a Nautiloid Orthoceratites from the Upper Devonian, polished on matrix, with clear details of the ornamentation well preserved, only a piece as in photo.

The Nautiloids (Nautiloidea Agassiz, 1847) are a subclass of Marine Cephalopods datated back to the upper Cambrian. The Orthoceras regulare is an extinct Mollusk Nautiloid, that lived in middle Ordovician.
His remains were found in Estonia, Lithuania, Sweden, Belarus and Ukraine. Historically, however, the name Orthoceras has been erroneously applied to a quantity of fossil nautiloids conical, from all parts of the world.
The shell of this animal was elongated and narrow, with a bottleneck in the middle of the chamber body. The surface was decorated with a network of complex drawings, typical of molluscs nautiloids. Many similar species are currently classified in the genus Michelinoceras.
Many fossils of Orthoceras and allied forms are usually found in gatherings such as to form the bedrock. Based on studies on the distribution and size of shells, some scientists have speculated that these gatherings were the consequences of mass die after mating, as happens now in many cephalopods (though not in nautilus). This hypothesis has not completely convinced most scholars and leaves open other possibilities. Fossils of this type are particularly common in Ordovician rocks, but also extend into the Devonian rocks, well-known examples are found in Morocco, Scandinavia, the Alps and Iowa (USA).