Lot 126, Auction 3/19/2026: Polished Fossil Slab of Ammonites & Orthoceras Shells

$650.00

In stock

North Africa, Morocco, Devonian Period, ca. 419.2 to 358.9 million years ago. A massive fossil stone slab polished in relief to reveal numerous ammonite shells and elongated Orthoceras fossils preserved within a dense stone matrix. The contrasting textures between the smooth fossil forms and the finely patterned fossilized background create a striking natural composition. An impressive large-scale specimen well suited for architectural display or as a dramatic decorative statement piece. Size: 37″ L x 22″ W (94 cm x 55.9 cm)

Prehistoric ‘straight’ cephalopods include straight ammonoids called orthoceras. Cephalopod evolution began during the Late Cambrian Period. Some of these creatures evolved into semi-coiled forms, eventually giving rise to coiled cephalopods like ammonites and nautili. Straight cephalopods were among the most advanced invertebrates of their time, with eyes, jaws, and a sophisticated nervous system. These creatures were predators that swam freely using a jet propulsion system by squirting water from their bodies. They had tentacles and ink sacs, much like present-day squid. Except for belemnites, cephalopods had external shells with hollow internal chambers separated by walls called septa. A tube called the siphuncle connected the body with the chambers allowing the animal to fill them with water or air, changing its buoyancy in order to rise or drop in the ocean. Only the last and largest chamber was occupied by the living animal!

Condition: Professionally prepared with a high polish and relief carving to the larger fossils as shown. Loss to Orthoceras shell along the edge.

Provenance: private Colorado, USA collection; ex-Keystone Auctions, York, Pennsylvania, USA

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