RARE Subptychoceras yubarense Fossil Heteromorph Ammonite | Campanian Cretaceous | Oriba Japan | Authentic Marine Fossil

Description

Offered here is a RARE and scientifically significant fossil of Subptychoceras yubarense, an extinct heteromorph ammonite from the Campanian Stage of the Late Cretaceous Period, unearthed from the marine sediments of Oriba, Japan. This remarkable specimen belongs to a genus known for its unique U-shaped or hook-like coiling pattern, offering insight into the evolutionary experimentation of ammonite shell geometry.

Fossil Overview:

• Species: Subptychoceras yubarense
• Fossil Type: Heteromorph Ammonite
• Geological Age: Campanian Stage, Late Cretaceous (~83.6 – 72.1 million years ago)
• Location: Oriba, Japan
• Formation: Yezo Group (Upper Cretaceous marine strata)
• Scale Reference: 1cm cube shown in photos
• Photo: Actual specimen shown – you will receive exactly what is pictured
• Authenticity: Supplied with a Certificate of Authenticity

Scientific Classification:

• Kingdom: Animalia
• Phylum: Mollusca
• Class: Cephalopoda
• Order: Ammonitida
• Superfamily: Turrilitoidea
• Family: Diplomoceratidae
• Genus: Subptychoceras
• Species: Subptychoceras yubarense
• First Described By: Yabe & Shimizu, 1926

Geological and Environmental Context:

This fossil was preserved in the marine shale and mudstone of the Yezo Group, a rich geological unit stretching along Hokkaido and northern Honshu in Japan. During the Late Cretaceous, this region was part of a deep marine forearc basin environment, with offshore sedimentation that created ideal conditions for the preservation of cephalopod fossils.

The Campanian Stage represents one of the most diverse and prolific periods in ammonite evolution. The family Diplomoceratidae, to which Subptychoceras belongs, developed unusual shell morphologies likely related to floating or drifting life habits, rather than active swimming.

Morphological Features:

• Hooked or U-shaped shell coil, typical of the heteromorph form
• Compact body chamber with slightly inflated whorls
• Presence of subtle ribbing or smooth ornamentation along the shell depending on preservation
• Its morphology suggests planktonic or nekto-benthic habits in the water column
• The shape may have served as a stabilizer or buoyancy aid in deeper marine zones

Notable Characteristics:

• A rare example of ammonite experimentation in shell design
• Excellent preservation of diagnostic morphology
• Originates from a region less commonly represented in Western collections
• Strong collector appeal due to unique shape and biogeographic rarity
• Offers educational and visual insight into ammonite diversity near the close of the Mesozoic Era

Summary:

• Species: Subptychoceras yubarense
• Age: Campanian, Late Cretaceous (~80 million years ago)
• Provenance: Oriba, Japan
• Geological Formation: Yezo Group
• Type: Heteromorph Ammonite
• Authenticity: Certificate Included
• Photo: Exact item shown
• Size Reference: Scale cube = 1cm

Note:

All of our Fossils are 100% Genuine Specimens & come with a Certificate of Authenticity.

The fossil you receive has been carefully sourced, selected, cleaned, and treated to highlight its natural features and ensure its scientific and visual integrity.