7990

• UCREFRP Catalog Number: 7990
• Author: Tyus, H. M.
• Title: Razorback Sucker ‎(
• USFW Year: 1997.
• Copyright Material: NO

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PARTI
INTRODUCTION

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History
The razorback sucker, Xyrauchen texanus (Abbott), an endemic fish of the Colorado
River basin of the American West (Fgure 1), is a member of the sucker family
(Catostomidae: Catostominae). Catostomids, a diverse and successful group of
freshwater fishes, are abundant in North America (Moyle and Cech 1988). Catostomids
occur in northeastern Siberia, Alaska, and from northern Canada to Mexico (Nelson
1994). The origins of North American suckers remains somewhat obscure due to an
incomplete fossil record. Oldest known North American catostomid specimens come
from Paleocene formations (ca. 53-65 mya; Lavender 1986). However, the
Catostomidae may have occurred earlier in northern latitudes where fossil records may
have been destroyed or covered by glaciers. The razorback sucker arose from an
ancient form that diverged very early from the main line of catostomid evolution (Miller
1958). Xyrauchen presumably originated by Pliocene and one "well-preserved"
Pleistocene specimen from Salton Sea, California has been identified as Xyrauchen
fexanus (Miller 1958, Minckley et al. 1986).
The razorback sucker is placed in the monotypic genus Xyrauchen, one of four genera
in the tribe Catostomini (Nelson 1994). The species was originally described in 1860
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