''Pacifastacus nigrescens'', the sooty crayfish, is an extinct species of

crayfish Crayfish are freshwater crustaceans belonging to the clade Astacidea, which also contains lobsters. In some locations, they are also known as crawfish, craydids, crawdaddies, crawdads, freshwater lobsters, mountain lobsters, rock lobsters, mu ...

in the family Astacidae. It was originally described in 1857 by

William Stimpson William Stimpson (February 14, 1832 – May 26, 1872) was a noted American scientist. He was interested particularly in marine biology. Stimpson became an important early contributor to the work of the Smithsonian Institution and later, direc ...

from the area around

San Francisco San Francisco (; Spanish language, Spanish for "Francis of Assisi, Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the List of Ca ...

, where it was once common in the creeks surrounding

San Francisco Bay San Francisco Bay is a large tidal estuary in the U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the big cities of San Francisco, San Jose, and Oakland. San Francisco Bay drains water from a ...

. The

signal crayfish The signal crayfish (''Pacifastacus leniusculus'') is a North American species of crayfish. It was introduced to Europe in the 1960s to supplement the North European ''Astacus astacus'' fisheries, which were being damaged by crayfish plague, but ...

, ''Pacifastacus leniusculus'' was introduced to California, probably in the 19th century, and since then, no sightings of ''P. nigrescens'' have been made; it is now believed to be

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

. Intensive searches of its former habitat have found that every site where it once occurred is now occupied by either the signal crayfish or ''

Procambarus clarkii ''Procambarus clarkii'', known variously as the red swamp crayfish, Louisiana crawfish or mudbug, is a species of cambarid crayfish native to freshwater bodies of northern Mexico, and southern and southeastern United States, but also introduc ...

''. The preserved specimen of male and female ''P. nigrescens'', suggests that scale bars for males is , while for females its . The size of the specimen was for males, while females were .

References

Astacidae Freshwater crustaceans of North America Endemic fauna of California Crustaceans described in 1857 Extinct invertebrates since 1500 Extinct crustaceans Extinct animals of the United States Taxa named by William Stimpson {{Crayfish-stub