TED 142

INTRODUCTION

For almost 30 years North American herpetologists have been making
extensive collections of reptiles and amphibians in Mexico. Some parts
of the country, because of their accessibility, soon became relatively
well known; other regions lying off the beaten path were bypassed or
inadequately sampled. Principally in the last decade herpetologists have
been entering regions from which no collections previously were
available in an attempt to fill gaps in known distributions and to
discover unknown species of animals. In 1950 Dr. Donald D. Brand led an
exploration party from the University of Texas to the poorly explored
and faunistically unknown region of southwestern Michoacan. James A.
Peters accompanied Brand and collected amphibians and reptiles. In 1951
I welcomed the opportunity to accompany Brand on a second expedition to
southwestern Michoacan. Such was the beginning of my interest in the
herpetofauna of the region. I have been fortunate to return to Michoacan
on four successive trips, all of which had as their purpose the
accumulation of data on the herpetofauna that would result in a survey
of the component species and an analysis of their distribution.

My original intention was to amplify Peters' (1954) study based on the
collections made by him in 1950 and by me in 1951 in the Sierra de
Coalcoman. But it soon became evident that in order to understand the
relationships of the herpetofauna of the Sierra de Coalcoman, the
species inhabiting the Tepalcatepec Valley and adjacent mountain ranges
would have to be studied. In the course of making that study I examined
all specimens from Michoacan already in museums.

There have been few detailed herpetofaunal studies in Mexico. The first
such study of any consequence was that by Bogert and Oliver (1945) on
the herpetofauna of Sonora. In that paper the authors analyzed the fauna
from a geographic view and showed the transition from tropical species
in the southern part of the state to members of the Sonoran Desert
assemblage to the north. Martin (1958) made a detailed study of the
herpetofauna of the Gomez Farias region in southern Tamaulipas; he
emphasized the ecological distribution of amphibians and reptiles in
that region with special reference to cloud forests. Duellman (1958c)
presented a preliminary geographic analysis of the herpetofauna of
Colima with special reference to the continuity of the species
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