Object Record

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Object Name Placenticeras meeki
Object Description Nearly complete specimen of the extinct Late Cretaceous cephalopod, Placenticeras meeki embedded in a limestone concretion. Characterized by a compressed, involute, planispiral shape with very slight ribbing on the flank and small shallow tubercules on the umbilical shoulder. The venter is narrow and flat. Original mother-of-pearl shell material is present at the umbilicus and up to the umbilical shoulder. Although the mother-of-pearl missing on the rest of the specimen, suturing and sculpturing of the septal walls is obvious. The suture pattern is ammonitic with complex folioles and lobules. Approximately 24 cm across the largest diameter of the shell.

Ammonites like this specimen are distant relatives of modern squid and octopi, and can be commonly found in the Pierre Shale of South Dakota.
Place of Origin South Dakota
Dimensions H-9 W-21 L-25 cm
Catalog Number 00.13109