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Lot 0211
North Africa, Anti-Atlas Mountains - Southern Morocco, Devonian period, ca. 410 million years ago. A superb, unbroken giant slab filled with wonderful naturally occurring orthoceras fossils that was once part of the prehistoric ocean floor over 400 million years ago. As these forms of prehistoric squid were covered in ocean sediments prior to fossilization, the majority of the creatures will be facing in the same relative position, having been lined up by currents on the sea floor prior to being buried. The fossils are exposed and given a high polish to better view the creatures from their surrounding matrix. The slab features very high relief as well as dramatic texture and detail. Prehistoric 'straight' cephalopods include straight ammonoids called orthoceras. Cephalopod evolution began during the Late Cambrian Period. Cephalopod bodies were predominantly elongate with conical shells. Some of these creatures evolved into semi-coiled forms, eventually giving rise to coiled cephalopods like ammonites and nautili. Size: 36" W x 27" H (91.4 cm x 68.6 cm)

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. Belemnites were different in that they had internal shells called "guards" which were covered with the soft, muscular tissues of their bodies. These shells were also chambered but much less complex than the straight varieties of nautiloids and ammonoids.

Provenance: acquired in 2012 from a French collection

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Intact, with no repair or restoration.

Buyer's Premium

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Massive Fossil-Rich Prehistoric Orthoceras Slab

Estimate $2,700 - $4,000Jun 21, 2018
Louisville, CO, USA