Oregonia (crab) explained

Oregonia is a genus of crabs, comprising two extant species^[1] and one fossil species:^[2] It is classified in the family Oregoniidae under the spider crab superfamily Majoidea.^[1]

Description

The members of the genus are characterized by subtriangular or suboblong carapaces moderately covered with small protrusions (tubercles). They have large spines on the rear margins of the eye orbits (the postorbital spine) that are situated quite far from the eyestalks. The male chelipeds are elongated. The palms (manus) of the claws are long, compressed, and widen on the outer ends. The walking legs (pereiopods) are slender and decrease in length regularly towards the back. The abdomen (pleon) has seven segments.^{[3] [4]}

Species

Three species are currently recognized under the genus:

• Oregonia bifurca Rathbun, 1902 – the split-nose crab, found in deep waters of the northern Pacific Ocean, from the Bering Sea to the waters off British Columbia
• Oregonia gracilis Dana, 1851 – the graceful decorator crab, found in shallow waters of the northern Pacific Ocean, from off Japan to the waters off California
• †Oregonia spinifera Schweitzer, Feldmann, González-Barba & Vega, 2002^[5] – a fossil species from the Oligocene El Cien Formation of Baja California, Mexico^[6]

The previously described species O. longimana, O. mutsuensis and O. hirta have all been subsumed into O. gracilis.^{[4] [7]} O. hirta in particular was misidentified as a separate species due to the sexual dimorphism exhibited by majoid crabs. They were actually the females of O. gracilis.^[4]

See also

• Decorator crab

Notes and References

1. Peter Davie . 2010 . Oregonia Dana, 1851 . 439494 . January 11, 2012.
2. . 2009 . Suppl. 21 . 1–109 . A classification of living and fossil genera of decapod crustaceans . Sammy De Grave . N. Dean Pentcheff . Shane T. Ahyong . etal.
3. Book: Mary J. Rathbun . The Spider Crabs of America . Government Printing Office. Washington. Bulletin (United States National Museum) 129. 1925. 71–79. Mary J. Rathbun .
4. Book: John S. Garth . Brachyura of the Pacific Coast of America, Oxyrhyncha. Los Angeles. The University of Southern California Press. Allan Hancock Pacific Expeditions. Volume 21, Part 1. 1958. 135 - 141.
5. Book: Francisco J. Vega, Torrey G. Nyborg and María Del Carmen Perrilliat . 2006 . Mesozoic and Tertiary decapod Crustacea from Mexico . Studies on Mexican Paleontology . Topics in Geobiology . 24 . 79–100 . 10.1007/1-4020-3985-9_5. 1-4020-3882-8 .
6. Carrie E. Schweitzer . Rodney M. Feldmann . Gerardo González-Barba . Francisco J. Vega . 2002 . New crabs from the Eocene and Oligocene of Baja California Sur, Mexico and an assessment of the evolutionary and paleogeographic implications of Mexican fossil decapods . Journal of Paleontology . 76 . 6 (Suppl.) . 1–43 . 10.1666/0022-3360(2002)76[1:ncftea]2.0.co;2. 128993593 .
7. Masatsune Takeda . 1987 . Oregonia mutsuensis Yokoya, 1928, as a synonym of O. gracilis Dana, 1851 . Zoology, National Science Museum, Tokyo . 20 . 133–136 .