filter route A term introduced by the American palaeontologist G. G.Simpson in 1940 to describe a faunal migration route across which the spread of some animals is very likely, but the spread of others is correspondingly improbable. The route thus filters out part of the fauna, but permits the rest to pass. Deserts and mountain ranges provide examples of filter routes.

filter route A term introduced by the American palaeontologist G. G. Simpson in 1940 to describe a faunal migration route across which the spread of some animals is very likely but the spread of others is correspondingly improbable. The route thus filters out part of the fauna, but permits the rest to pass. Deserts and mountain ranges provide examples of filter routes.

filter route Term introduced by the American palaeontologist G. G.Simpson (1940), to specify a faunal migration route along which the spread of some animals is very likely but the spread of others is improbable. The route thus filters out part of the fauna, but permits the rest to pass. Deserts and mountain ranges provide examples of filter routes.