Skip to main content
Go to accessibility notice


    Mosasaur Skeleton
    Platecarpus sp.
    Late Cretaceous
    Smoky Hill Chalk Member, Niobrara Formation
    Kansas, USA

    The Western Interior Seaway, also aptly known as the Cretaceous Seaway, existed as a large inland sea that effectively split the North American continent in two. Mosasaurs were apex predators of the time, and Platecarpus ("flat wrist") was a medium-sized variety of mosasaur that roamed and dominated those ancient waters preying on a variety of aquatic fauna. The giant predatory marine creature was a "sea monster" during the Late Cretaceous and was characterized by a unique skull structure with a short skull with fewer teeth than other mosasaurs and an elongate down-turned tail. The marine creature also boasted prominent "steering" flippers and conical, pointed teeth. A variety of mosasaur is the State Marine Fossil of Kansas, so it is no surprise this spectacular skeletal specimen originated from the iconic Smoky Hill Chalk Member of the renowned Niobrara Formation in the western section of the Sunflower State. Weighing some 300 to 400 pounds (136 to 181 kilograms), this spectacular piece consists of a giant mosasaur measuring a colossal 18 feet 6 inches (5.6 meters) in a partial curving position on a matrix presentation.

    The fossil dates back approximately 80+ million years ago and evidences a superb preservation as well as an expert restoration that results in this striking museum-quality example designed to be wall mounted. The piece features a "French Wedge" with a 4 foot (1.2 meters) by 6 foot (1.8 meters) board matching an attachment with a 40 degree angle to facilitate secure installation. The slab measures approximately 11 feet 7 inches (3.5 meters) by 5 feet 11 inches (1.8 meters). Massive in both terms of the fossil skeleton as well as the overall rock, this show-stopping specimen offers further attributes evidencing its singularity as a top-quality example of the variety. A little over 2 feet (0.6 meters) of the caudal (tail) section has been reconstructed, but the majority of the fossil is in outstanding condition, with excellent preservation. The contrast of the dark brown fossilized bone, with the stark white background, and light brown color of the matrix results in an ideal display specimen. Ancient shark teeth were found with the fossil, and there are shark tooth bite marks on the ribs. Most impressive, there is evidence of a rare and uncommon soft tissue preservation on the neural spine of several of the caudal (tail) vertebrae.

    The combination of its outstanding quality, enormous size and visual aesthetics results in a transcendent fossil worthy of any significant private or institutional collection. This monster still looks dominant today.
    Overall Measurements: 138.96 x 70.92 inches (352.95 x 180.13 cm)

    (Photos courtesy of Jon Blum.)

    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. Heritage does not guarantee the condition of frames and shall not be liable for any damage/scratches to frames, glass/acrylic coverings, original boxes, display accessories, or art that has slipped in frames. All lots are sold "AS IS" under the Terms & Conditions of Auction.

    Auction Info

    Auction Dates
    March, 2021
    19th Friday
    Bids + Registered Phone Bidders: 0
    Lot Tracking Activity: N/A
    Page Views: 6,600

    Buyer's Premium per Lot:
    25% on the first $300,000 (minimum $49), plus 20% of any amount between $300,000 and $3,000,000, plus 12.5% of any amount over $3,000,000 per lot.

    Shipping, Taxes, Terms and Bidding
    Charges to be determined based on Actual Shipping Costs incurred. Note: Additional invoice may follow original. Please contact us for more information. Sales Tax information

    Important information concerning Sales Tax and Resale Certificates. Learn More

    Terms and Conditions  |  Bidding Guidelines and Bid Increments |  Glossary of Terms

    Sold on Mar 19, 2021 for: Sign-in or Join (free & quick)
    Track Item

    Heritage membership

    Join Now - It's Free

    1. Past Auction Values (prices, photos, full descriptions, etc.)
    2. Bid online
    3. Free Collector newsletter
    4. Want List with instant e-mail notifications
    5. Reduced auction commissions when you resell your
    Consign now
    • Cash Advances
    • More Bidders
    • Trusted Experts
    • Over 200,000 Satisfied Consignors Since 1976
    Consign to the 2021 November 16 Silver & Vertu Signature Auction - Dallas.

    Learn about consigning with us

    As a consignor to your recent silver, art glass and fine art auction, I want you to know how pleased I am with my decision to consign with Heritage
    C. B. ,
    Leesburg, VA
    View More Testimonials receives more traffic than any other auction house website. (Source:

    Video tutorial

    Getting the most out of search