Ammonite Fossil Placenticeras meeki Late Cretaceous Near Hell Creek...

Ammonite Fossil Placenticeras meeki Late Cretaceous Near Hell Creek Formation South Dakota, USA Ammonites are known to occur inside sedimentary nodules and, in particular, associated with Septarian mud concretions, but this expansive specimen consists of a massive Placenticeras that has fossilized into a Septarian nodule itself!! While the shape, form, and complex suture lines are all-Ammonite, the presence of a huge linear cavity bisecting the ancient cephalopod, partially filled with golden Calcite and brownish Baryte, indicates Septarian. Part of the compressed prehistoric shell even displays a crystalline cavity of drusy nature. The fused specimen has an offset 'double' whorl on one side and other odd characteristics due to the complexity of the form and composition of the fossil. Measuring over 15 inches (38 cm) at its maximum diameter, this decorative and intriguing display offering is most unusual, extensive, and has an inherent variety to its two primary sides. This tells more of a story than paints a picture with its looks but is certainly a strange and complicated version of a popular Ammonite type dating to the Late Cretaceous of South Dakota. This is a paleontological marvel of sorts with multiple, and yet indescribable, attributes. Measurements: 15.35 x 12.60 x 1.57 inches (39.00 x 32.00 x 4.00 cm) HID09710052018 © 2022 Heritage Auctions | All Rights Reserved