Definition: The number of fossil occurrences in the Paleobiology Database (https://paleobiodb.org) that are identified as belonging to a particular taxon or any of its subtaxa.
Definition: Eye-spots which may be set into a pit to reduce the angles of light that enters, to allow the organism to deduce the angle of incoming light. Lens-like structures may be present, but stemmata, unlike lens eyes, cannot form an image, either for lack of refractive power or retinal resolution.
