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    Description

    IRIDESCENT AMMONITE

    Superb Iridescent Ammonite
    Sphenodiscus lobatus
    Late Cretaceous, Fox Hills Formation, Timber Lake Member
    Dewey County, South Dakota, USA

    Ammonites are an amazing and prolific group of marine cephalopods which went extinct at the end of the Cretaceous, along with the dinosaurs, some 65 million years ago. Characterized by complex suture lines and marginal placement of the "siphuncle" (an organelle used to regulate buoyancy), Ammonites were abundant worldwide before they summarily disappeared from the ancient oceans. The genus Sphenodiscus was a member of the acanthoceratacean ammonite group which were some of the last ammonoids to have evolved before the mass K-T extinction.

    This superlative invertebrate fossil is a beautiful deep red Ammonite preserved in a sedimentary concretion. The incredible color of the iridescent shell exhibits an opalescence as light reflecting off the surface explodes into a brilliant crimson on this museum quality piece. This large specimen is considered one of the best of its variety ever collected, and the gemmy Ammonite cradled in its grayish-tan granular matrix measures a substantial 13 inches (33 cm) at its maximum diameter.

    The fossilized shells of Sphenodiscus can be characterized by overlapping whorls and the small umbilicus which this fine specimen does exhibit. The outer surface is smooth, and the nacre has been preserved to reveal this stunning red coloration so sought after by collectors of this highest level of Ammonite. The shell has one section where the red color is not prominent; otherwise, the fossil is beyond reproach. This is a museum quality specimen worthy of any collection of superb Ammonites, or really any kind of fossils for that matter. This specimen has resided in a museum collection for the past several years and is certainly deserving of another fine place to call home.
    Overall Measurements: 17.0 x 15.5 x 6.0 inches (43.2 x 39.4 x 15.2 cm)
    Offered at no reserve.


    Condition Report*: Condition report available upon request.
    *Heritage Auctions strives to provide as much information as possible but encourages in-person inspection by bidders. Statements regarding the condition of objects are only for general guidance and should not be relied upon as complete statements of fact, and do not constitute a representation, warranty or assumption of liability by Heritage. Some condition issues may not be noted in the condition report but are apparent in the provided photos which are considered part of the condition report. Please note that we do not de-frame lots estimated at $1,000 or less and may not be able to provide additional details for lots valued under $500. All lots are sold "AS IS" under the Terms & Conditions of Auction.

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    Auction Info

    Auction Dates
    October, 2015
    4th Sunday
    Bids + Registered Phone Bidders: 2
    Lot Tracking Activity: N/A
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