Mammalian Characteristics


Modern mammals have a number of features that can be used to characterize them. Some of these are unique to mammals among the living vertebrates, others characteristic of most or all living mammals but also occur in some other vertebrate groups. "Modern" and "living" are emphasized here because a number of fossil mammal-like reptiles display morphological characters that we think of as typically mammalian (and we presume non-fossilizable "mammalian" characters also were evolved in various taxa close to the ancestry of mammals). Although we have no difficulty in separating modern reptiles from modern mammals, the separation in the fossil record basically is arbitrary.

Characters Unique to Mammals Among Modern Vertebrates

Characters Typically Present in Mammals, but also Found Among Other Vertebrate Taxa

Although other features of mammals could be mentioned (and some will be further on), the above should sufficiently characterize the class.


Last Update: 16 Jan 2008

Centennial Museum and Department of Biological Sciences, The University of Texas at El Paso