RARE FOSSIL HETEROMORPH AMMONITES – PARASPINOCERAS PULCHERRIMUM AND COSTIDISCUS

Geological Age: Barremian Stage, Early Cretaceous (~129–125 million years ago)

Location: Drôme, France

From the Alice Purnell Collection

Comes with Certificate of Authenticity

This is a rare and striking paired specimen of two heteromorph ammonites: Paraspinoceras pulcherrimum and Costidiscus. Both genera are notable for their unique and unusual shell morphologies and represent distinct lineages of ammonite evolution during the Barremian stage of the Early Cretaceous period.

Collected from the marine limestone deposits of the Drôme region in southeastern France, this fossil encapsulates the ecological diversity and morphological experimentation that characterised ammonite evolution in the early Cretaceous seas. The matrix preserves both species in beautiful relief, offering a unique opportunity to observe differences in their ornamentation and coiling styles.

The specimen is carefully preserved and shown next to a 1cm scale cube for precise sizing. The photo is of the exact fossil you will receive. Sourced from the prestigious Alice Purnell Collection, this item includes a Certificate of Authenticity.

GEOLOGICAL & TAXONOMIC DETAILS:

• Species: Paraspinoceras pulcherrimum and Costidiscus sp.
• Age: Barremian Stage, Early Cretaceous
• Formation/Depositional Environment: Likely from shallow marine carbonate shelves of the pre-Alpine Drôme Basin, representing still, subtropical marine conditions
• Biozone (if available): Barremian ammonite zones are typically subdivided by the presence of Toxancyloceras, Imerites, and Gerhardtia species; Costidiscus often appears in Gerhardtia sartousiana subzone equivalents
• Morphology Features:
• Paraspinoceras pulcherrimum: Highly ornamented with spiny ribs and tubercles; shows loosely coiled to helically curved heteromorph form
• Costidiscus: More planispiral but with ornate ribbing, sometimes with ventral keels
• Order: Ammonitida
• Superfamily: Ancyloceratoidea
• Family: Paraspinoceratidae (for Paraspinoceras) and possibly Desmoceratidae (for Costidiscus)

SCIENTIFIC AND DISPLAY VALUE:

The coexistence of these two ammonite types makes this fossil a superb comparative piece for researchers, collectors, and educators. Paraspinoceras is prized for its flamboyant heteromorphic structure, while Costidiscus illustrates transitional ornamentation and shell form that helps paleontologists understand evolutionary trends during the Lower Cretaceous.

These ammonites are also biostratigraphically significant, as they contribute to the dating and correlation of Cretaceous marine strata across Europe and beyond.

INCLUDED WITH PURCHASE:

• The exact fossil specimen shown in the photographs
• Certificate of Authenticity
• 1cm scale cube shown in photo for reference
• Secure and professional packaging
• From the respected Alice Purnell Collection

SUMMARY:

A unique double-specimen of rare heteromorphic and planispiral ammonites from the Early Cretaceous seas of southeastern France. This fossil is ideal for anyone passionate about ammonites, paleontology, or museum-quality geological specimens.