Their suture patterns are like nature’s artwork. The internal walls (septa) dividing shell chambers create incredibly intricate, fractal-like patterns visible when fossils are polished. These "sutures" are unique to each species and help paleontologists identify and date them precisely.
Placenticeras meeki
Late Cretaceous, Pierre Shale
South Dakota, USA
This unusual-looking piece features an ammonite preserved in a sedimentary concretion. In this instance, "mud" formed around the fossil and hardened to rock which was ultimately broken open to reveal the nice surprise inside. This Placenticeras meeki displays intricate suture patterns on the smooth shell with areas of colorful mineral replacement whereby the Calcite has filled in certain cavities resulting in golden yellow sections on the fossil.
The Ammonite measures 10 inches (25.4 cm) in diameter and is nicely perched on the rock holding it. There is some exposed shell nacre on the fossil exhibiting an opalescence including green and pink shimmering coloration.
Overall Measurements: 10.75 x 9.5 x 5.75 inches (27.31 x 24.13 x 14.61 cm)
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