Equus species as stratigraphic markers reality or wishful thinking?

This paper addresses the use of fossil species of the horse Equus as strati graphic markers in the Pliocene and Pleistocene. Current research shows tha t the species recently so used do not succeed one another in orderly fashio n, but occur and co-occur at ages other than presupposed by the stratigraph ic schemes (usually earlier). Horse species should be identified on their m orphology, not on their stratigraphic age. 'Subspecies' of fossil horses do not conform to subspecies in zoology, as they lack a geographic range. The y thus lack taxonomic status and stratigraphic significance and should be a voided. (C) 1998 Elsevier Science Ltd. All right reserved.