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  • José H. Leal

An Ammonite in Burmese Amber



An Ammonite in Burmese Amber

Who doesn’t like amber? The result of the fossilization of plant resins, amber is a cool-looking, translucent, yellow-orange-brown substance that has been used in the manufacture of jewelry and decorative objects since the Stone Age. Amber is also known for its unique preservation properties, helping conserve otherwise hard-to-fossilize organisms, including small vertebrates, insects, spiders, and a plethora of other animals. Small animals are trapped within the slow-flowing but impervious, molasses-like resin, resting forever entombed within the material as it dries over extended periods. Fossilization of amber through geological time results in fundamental changes in the structure of the originally soft material. Given the terrestrial origin of the tree resins that give origin to amber, most of the animals trapped within, such as insects and spiders, are of terrestrial origin. A recent paper published in the Proceedings of the National Academy of Sciences described an exceptional, almost unique instance of an old, fossilized molluscan shell preserved in amber from Burma. Tinting Yu and colleagues recorded the presence of an ammonite shell preserved in amber for about 100 million years! Together with the 12 mm (about 0.5 inch) shell of a young Puzosia ammonite, the researchers found marine gastropod shells and terrestrial arthropods, including spiders, insects, and mites. The authors present a few hypotheses to explain the unusual presence of a marine fossil preserved in amber. The most plausible seems to be that the blob of resin traveled from the its mother-tree to a nearby patch of sandy beach, picking up land invertebrates first, then the marine shells, before setting in perpetuity as hard amber. Read the paper here.