Rare 5.25″ Proplanulites koenigi Fossil Ammonite, Jurassic, Lower Callovian, Ashton Keynes UK, Genuine with COA

Description

This listing features a Rare 5.25″ Fossil Ammonite of Proplanulites koenigi from the Lower Callovian Stage of the Jurassic Period, collected at Ashton Keynes, Wiltshire, United Kingdom. This large and well-preserved ammonite is a representative of a genus known for its refined morphology and importance in Jurassic biostratigraphy.

The photos show the actual specimen you will receive, professionally cleaned and carefully chosen for its exceptional preservation and scientific value.

Scale Rule Squares / Cube = 1cm — refer to the photo for full sizing and detail.

Key Geological and Scientific Information:

• Species: Proplanulites koenigi
• Fossil Type: Ammonite (extinct marine cephalopod)
• Geological Period: Jurassic
• Geological Stage: Lower Callovian (~164 million years ago)
• Location: Ashton Keynes, Wiltshire, England, UK
• Formation: Likely Kellaways Beds or associated Callovian marine clays
• Order: Ammonitida
• Superfamily: Haploceratoidea
• Family: Tulitidae (or closely related family, taxonomically debated)
• Described By: Sowerby, 1818

Morphology Features:

Proplanulites koenigi is characterised by a smooth, flattened, and compressed shell, with fine ribbing and a narrow venter. The coiling is involute to moderately evolute, with a visible umbilical area. The ribs are delicate, often fading toward the flanks, creating a clean and streamlined profile — a typical feature of Proplanulites species.

This specimen clearly exhibits the flattened whorls and subtle ribbing that define the species, making it an ideal piece for collectors or academic reference.

Depositional Environment:

This ammonite was deposited in a low-energy, offshore marine setting, likely within the fine silts and clays of the Kellaways Beds or similar Callovian strata. These conditions favoured the preservation of delicate shell structures and fine ornamentation.

Stratigraphic & Biozone Significance:

Proplanulites koenigi occurs within the Lower Callovian ammonite zones, frequently associated with the Kepplerites galilaeii Zone or slightly later subdivisions. It plays a supporting role in the subdivision of Middle Jurassic sequences across Europe and is useful in biostratigraphic correlation.

Scientific Importance:

This species is valued for its role in understanding Jurassic ammonite morphology and evolutionary development. It reflects a shift toward more compressed and less ornamented shell forms, marking a subtle evolutionary trend among Haploceratids during the Callovian.

Authenticity Guarantee:

All of our fossils are 100% genuine specimens, carefully selected and professionally prepared. Each fossil is supplied with a Certificate of Authenticity, verifying its species identification, locality, and geological age.

This Proplanulites koenigi ammonite is a rare and scientifically significant specimen — an excellent addition to any fossil collection, natural history display, or educational setting focused on Jurassic marine life.