Redescription of the presumed-extinct Miller Lake Lamprey, Lampetra minima

Lampetra minima, believed eradicated in 1958 and extinct, survives in upper tributaries of the historical Williamson drainage in Klamath and Lake Coun ties, Oregon. The species, the smallest known parasitic lamprey, was believ ed to be endemic to Miller Lake. Its current disjunct distribution includes Miller Creek, Jack Creek, and upper sections of the Williamson and Sycan R ivers. We compare new specimens with the type series and other Klamath Basi n lampreys and redescribe L. minima. It appears most similar to Lampetra le thophaga but is smaller (72-145 mn vs 115-170 mm TL), has a larger disc len gth (5.0-8.6% vs 4.2-6.4% TL), larger prebranchial length (11.0-17.0% vs 8. 8-13.7% TL), and larger eye (2.1-3.3% vs 1.4-2.3% TL). Klamath Basin Lampet ra differ from anadromous Lampetra tridentata in a single transition in cyt ochrome b, and L. minima have an additional, but not unique, transition. Ou r data do not support the suggestion that L. minima recently evolved from a L. tridentata-like ancestor; rather we suggest a more ancient separation a nd a sister relationship with L. lethophaga.