Macrofossils are not common in deep-marine mudstones of the Miocene Modelo Formation in southern California. A lucky find would be a partial or complete bony fish skeleton, but these are rare. Fish scales, however, can be locally common, but a collector needs to know what they look like. Before enrolling in my paleontology class, most of my students would find a fish scale and not even know what they were looking at.
The fish scales shown below are of late Miocene age and from the Modelo Formation (commonly referred to as the Monterey Formation). Each scale is about 10- to 15-mm-wide and represents a paper-thin imprint on bedding planes of mudstone. Identification as to the family or genus of fish is not a trivial process and requires very specialized knowledge. At the very least, however, their presence indicates an aquatic environment.
|Two late Miocene fish scales belonging to the same genus. There might be a third fish scale in|
the lower right-hand corner.
|Another late Miocene fish scale, genus different from the two shown in the photo above.|