Description
Calycoceras planicostatum Ammonite Fossil
This listing presents a superb Calycoceras planicostatum Ammonite Fossil from the Lower Cenomanian stage of the Late Cretaceous, collected in Sarthe, France. Dating to around 100–96 million years ago, this species represents a highly significant ammonite used in stratigraphic studies. The exact specimen shown in the photographs will be sent, pictured with a 1 cm scale cube for accurate sizing. All fossils are guaranteed 100% genuine and supplied with a Certificate of Authenticity.
Geological Context – Lower Cenomanian of Sarthe
This ammonite comes from the Lower Cenomanian chalk and marl deposits of Sarthe, a classic fossil-bearing region in northwestern France. During the Cenomanian, global sea levels were among the highest of the Phanerozoic, covering much of Europe beneath shallow, warm seas. These seas formed part of the expanding North Atlantic and Tethys Ocean systems, providing nutrient-rich waters that supported diverse marine life.
The Cenomanian is a particularly important interval because it marks the onset of the Late Cretaceous. Fossil-rich chalk sequences in France, including those of Sarthe, have been studied extensively and are globally recognised reference points for biostratigraphy. Ammonites from these deposits, including Calycoceras planicostatum, are crucial to defining the ammonite biozones that underpin the Cenomanian stage.
Species Overview – Calycoceras planicostatum
The specimen is identified as Calycoceras planicostatum, a species within the order Ammonitida, superfamily Acanthoceratoidea, and family Acanthoceratidae. Ammonites of the genus Calycoceras are notable for their moderately evolute shells, strong ribbing, and prominent tubercles.
Calycoceras planicostatum is distinguished by its relatively flat, evenly spaced ribs and robust tuberculation along the ventrolateral shoulders. The ribs are typically straight and regular, creating the “planicostate” appearance from which the species takes its name. These features make the fossil visually striking and scientifically diagnostic, allowing paleontologists to identify it confidently in the field and use it as a biostratigraphic marker.
Paleontological Importance
Calycoceras planicostatum is a highly significant index fossil for the Lower Cenomanian. Its narrow stratigraphic range and well-defined morphology make it invaluable for dating chalk and marl sequences across Europe. It plays a central role in defining the ammonite biozones of the Lower Cenomanian, enabling precise correlation of marine sediments between distant localities.
The species also reflects the evolutionary innovations of the Acanthoceratidae, a diverse family of ammonites that dominated the mid to Late Cretaceous seas. Its strong ornamentation, with bold ribs and tubercles, illustrates both defensive adaptations against predators and hydrodynamic refinements for active swimming in open water.
Collector’s and Educational Value
This Calycoceras planicostatum ammonite fossil is a desirable specimen for serious collectors of Cretaceous fossils. Its provenance from Sarthe, France, enhances its importance, as this region has yielded some of the most scientifically studied ammonites of the Cenomanian. The bold ribbing and striking ornamentation make it an attractive display fossil, while its role as a zonal index fossil makes it equally valuable for academic collections.
For students and educators, this fossil provides an excellent teaching example, demonstrating ammonite morphology, Cenomanian stratigraphy, and the paleoecology of Late Cretaceous marine environments.
Guarantee of Authenticity
- 100% genuine Calycoceras planicostatum ammonite fossil
- Supplied with a Certificate of Authenticity
- The exact specimen shown in the photographs will be sent
This is a rare opportunity to acquire a scientifically significant and beautifully preserved Calycoceras planicostatum Ammonite Fossil from the Lower Cenomanian of Sarthe, France, an essential addition to any Cretaceous fossil collection.
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