Amaltheus striatus Fossil Ammonite Jurassic Middle Lias Whitby UK Certified | Rare Runswick Bay Collectible from Yorkshire Coast

Description

Authentic Amaltheus striatus Fossil Ammonite from Whitby

This listing offers a genuine Amaltheus striatus fossil ammonite, collected from the Middle Lias (Jurassic) deposits of Runswick Bay, Whitby, Yorkshire, United Kingdom. Amaltheus ammonites are among the most distinctive fossils of the British Jurassic, noted for their elegant ribbing and classic coiled form. The fossil pictured is the exact specimen you will receive, shown with a 1 cm scale cube for accurate measurement.

All of our fossils are 100% genuine specimens and come complete with a Certificate of Authenticity, making this a perfect choice for collectors, educators, or anyone with a passion for natural history.

Geological Context – Middle Lias, Jurassic of Whitby

The specimen originates from the Middle Lias (Lower Jurassic, approx. 183–174 million years ago), part of the Blue Lias and associated formations exposed along the Yorkshire coast. Runswick Bay, near Whitby, is world-famous for its fossil beds, which preserve ammonites, belemnites, marine reptiles, and other iconic Jurassic fauna.

The ammonites of the genus Amaltheus, including A. striatus, are important index fossils used by geologists to define specific zones within the Lias sequence. Their abundance, rapid evolutionary changes, and distinctive shell morphology make them key markers for correlating Jurassic strata across Europe.

Fossil Type and Scientific Classification

• Species: Amaltheus striatus
• Genus: Amaltheus
• Family: Amaltheidae
• Superfamily: Eoderoceratoidea
• Order: Ammonitida

The genus Amaltheus is well known from the Lias deposits of northern Europe, and A. striatus is one of its most recognisable species, prized by collectors for its ribbed whorls and striking appearance.

Morphological Features

This specimen displays the diagnostic traits of Amaltheus striatus:

• A planispiral, tightly coiled shell with a moderately involute form.
• Strong, evenly spaced ribs running across the flanks, giving the shell a striated texture.
• A rounded venter (outer margin), often with ribbing continuing across.
• Clear suture lines where internal chamber walls joined the shell exterior.

These features reflect both the taxonomic placement of the ammonite and its adaptations to life as a fast-swimming predator in Jurassic seas. The ribbing likely strengthened the shell against water pressure while maintaining buoyancy.

Scientific and Collector Importance

Amaltheus striatus is highly valued as an index fossil for the Middle Lias. Its presence in the stratigraphic record helps define the Amaltheus Zone, an internationally recognised biozone within the Lower Jurassic. This makes it important to geologists for dating and correlating Jurassic marine deposits.

For collectors, this fossil represents a classic Whitby ammonite, combining both scientific significance and aesthetic appeal. Its sharp ribbing and coiled form make it instantly recognisable and a desirable addition to any collection of British or European fossils.

Depositional Environment

During the Early Jurassic, the Whitby coast was covered by shallow seas, part of the larger marine system of the Tethys Ocean. These waters were rich in marine life, from ammonites and belemnites to large predators like ichthyosaurs and plesiosaurs. Fine sedimentation in these environments allowed for the excellent preservation of ammonite shells such as Amaltheus striatus.

Guarantee of Authenticity

All fossils we sell are 100% genuine specimens, hand-selected for their preservation and scientific value. Each comes with a Certificate of Authenticity, providing assurance of provenance. The photographs show the exact specimen you will receive, with a scale cube for reference.

This Amaltheus striatus fossil ammonite from the Middle Lias of Runswick Bay, Whitby is a rare opportunity to own a scientifically significant and visually striking example of Britain’s Jurassic heritage.