Nearly half of the known species of mammals alive today (more than 1600)
are rodents or "gnawing mammals" (Nowak and Paradiso, 1983). The
diversity of rodents is greater than that of any other order of mammals.
Thus, it is not surprising that the fossil record of this order is
extensive and fossil material of rodents from the Tertiary is known from
all continents except Antarctica and Australia. The purpose of this book
is to compile the published knowledge on fossil rodents from North
America and present it in a way that is accessible to paleontologists
and mammalogists interested in evolutionary studies of ro- dents. The
literature on fossil rodents is widely scattered between journals on
paleontology and mammalogy and in-house publications of museums and
universities. Currently, there is no single source that offers ready
access to the literature on a specific family of rodents and its fossil
history. This work is presented as a reference text that can be useful
to specialists in rodents (fossil or recent) as weIl as mammalian
paleontologists working on whole faunas. Because the diversity of
rodents in the world is essentially limitless, any monograph that
included all fossil rodents would similarly be limitless. Hence, this
book is limited to the re cord of Tertiary rodents of North America. The
several species of South American (caviomorph) rodents that invaded
North America near the end of the Tertiary are also not included in this
text.