The family Polychelidae contains thirty-four species of blind, benthic lobster-like crustaceans. They are found throughout the world's tropical, sub-tropical and temperate oceans, including the Mediterranean Sea and the Irish Sea. See genus (mathematics) for the use of the term in mathematics. ... In biology, a species is the basic unit of biodiversity. ... This article is about the year 2000. ... Charles Wyville Thomson Professor Sir Charles Wyville Thomson (March 5, 1830 - March 10, 1882), professor of zoology and chief scientist on the Challenger expedition. ... 1873 was a common year starting on Wednesday (see link for calaber). ... This article is about the year 2000. ... This article is about the year 2000. ... Dr. Mary Jane Rathbun (January 11, 1860 — April 4, 1943) was an American marine biologist. ... 1906 was a common year starting on Monday (see link for calendar). ... 1878 was a common year starting on Tuesday (see link for calendar). ... Alfred William Alcock (1859 - 1933) was a British naturalist. ... 1894 was a common year starting on Monday (see link for calendar). ... 1878 was a common year starting on Tuesday (see link for calendar). ... 1878 was a common year starting on Tuesday (see link for calendar). ... Dr. Mary Jane Rathbun (January 11, 1860 — April 4, 1943) was an American marine biologist. ... 1906 was a common year starting on Monday (see link for calendar). ... Alphonse Milne-Edwards (October 13, 1835 _ April 21, 1900) was a French ornithologist. ... 1880 was a leap year starting on Thursday (see link for calendar). ... 1862 was a common year starting on Wednesday (see link for calendar). ... This article is about the year 2000. ... 1878 was a common year starting on Tuesday (see link for calendar). ... 1878 was a common year starting on Tuesday (see link for calendar). ... Alfred William Alcock (1859 - 1933) was a British naturalist. ... 1878 was a common year starting on Tuesday (see link for calendar). ... This article is about the year 2000. ... 1878 was a common year starting on Tuesday (see link for calendar). ... This article is about the year 2000. ... 2002 (MMII) is a common year starting on Tuesday of the Gregorian calendar. ... 1878 was a common year starting on Tuesday (see link for calendar). ... 2002 (MMII) is a common year starting on Tuesday of the Gregorian calendar. ... Smith can refer to a person who practices smithing, to a very common family name or to part of a place name or location. ... 1884 is a leap year starting on Tuesday (click on link to calendar). ... 1893 was a common year starting on Sunday (see link for calendar). ... 1952 was a leap year starting on Tuesday (link will take you to calendar). ... Alfred William Alcock (1859 - 1933) was a British naturalist. ... 1894 was a common year starting on Monday (see link for calendar). ... This article is about the year 2000. ... Smith can refer to a person who practices smithing, to a very common family name or to part of a place name or location. ... 1880 was a leap year starting on Thursday (see link for calendar). ... 1878 was a common year starting on Tuesday (see link for calendar). ... This article is about the year 2000. ... Eugène Louis Bouvier (1856 - 1944) was a French entomologist and carcinologist. ... 1917 (MCMXVII) was a common year starting on Monday of the Gregorian calendar (see link for calendar) or a common year starting on Tuesday of the Julian calendar. ... 1893 was a common year starting on Sunday (see link for calendar). ... 1905 (MCMV) was a common year starting on Sunday (see link for calendar). ... 1862 was a common year starting on Wednesday (see link for calendar). ... 1873 was a common year starting on Wednesday (see link for calaber). ... Alphonse Milne-Edwards (October 13, 1835 _ April 21, 1900) was a French ornithologist. ... 1880 was a leap year starting on Thursday (see link for calendar). ... 1893 was a common year starting on Sunday (see link for calendar). ... 1875 was a common year starting on Friday (see link for calendar). ... 1920 (MCMXX) is a leap year starting on Thursday (link will take you to calendar) // Events January January 7 - Forces of Russian White admiral Kolchak surrender in Krasnoyarsk. ... In biology, a species is the basic unit of biodiversity. ... See also Blindness (novel) Blindness can be defined physiologically as the condition of lacking visual perception. ... In marine geology and biology, benthos are the organisms and habitats of the sea floor; in freshwater biology they are the organisms and habitats of the bottoms of lakes, rivers, and creeks. ... Subfamilies and Genera Neophoberinae Acanthacaris Thymopinae Nephropsis Nephropides Thymops Thymopsis Nephropinae Homarus Nephrops Homarinus Metanephrops Eunephrops Thymopides Clawed lobsters comprise a family (Nephropidae, sometimes also Homaridae) of large marine crustaceans. ... Classes Remipedia Cephalocarida Branchiopoda Ostracoda Maxillopoda Malacostraca The crustaceans (Crustacea) are a large group of arthropods (55,000 species), usually treated as a subphylum. ... The tropics are the geographic region of the Earth centered on the equator and limited in latitude by the two tropics: the Tropic of Cancer in the north and the Tropic of Capricorn in the southern hemisphere. ... Subtropical (or semitropical) areas are those adjacent to the tropics, usually roughly defined as the ranges 23. ... In geography, temperate latitudes of the globe lie between the tropics and the polar circles. ... The worlds oceans as seen from the South Pacific Ocean (from Okeanos, Greek for river, the ancient Greeks noticed that a strong current flowed off Gibraltar, and assumed it was a great river); covers almost three quarters (71%) of the surface of the Earth, and nearly half of the... Satellite image The Mediterranean Sea is a part of the Atlantic Ocean almost completely enclosed by land, on the north by Europe, on the south by Africa, and on the east by Asia. ... Relief map of the Irish Sea. ...

Anatomy

The family Polychelidae is notable for the number of chelate (clawed) limbs, with either four or all five pairs of pereiopods bearing claws. This gives rise to the scientific names Polycheles (many-clawed) and Pentacheles (five claws). The first pair of periopods are greatly elongated, but often become broken off while specimens are being brought to the surface. The rostrum is very short or absent, and, although eyestalks are present, the eyes are absent. This family can be seen as evidence of the transition from shrimp-like animals to lobster-like animals, since they possess a number of primitive characters (plesiomorphies), such as the pointed telson, in contrast to the rounded telson in lobsters. A claw is a curved pointed growth found at the end of a toe or finger, or in arthropods, of the tarsus. ... Antennules Pereiopods Carapace Pleopods Uropods Telson The body of a decapod crustacean is made up of nineteen body segments grouped into two main body parts, the cephalothorax and the abdomen. ... In biology, binomial nomenclature is a standard convention used for naming species. ... Rostrum can mean one of several different things: A rostrum (Latin beak) is an anatomical structure resembling a birds beak, such as the snout of crocodiles or dolphins or the part of the carapace of a crustacean. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Superfamilies and families Alpheoidea Alpheidae - snapping shrimps Barbouriidae Hippolytidae Ogyrididae Atyoidea Atyidae Bresilioidea Agostocarididae Alvinocarididae Bresiliidae Disciadidae Mirocarididae Campylonotoidea Bathypalaemonellidae Campylonotoidae Crangonoidea Crangonidae Glyphocrangonidea Galatheacaridoidea Galatheacarididae Nematocarcinoidea Eugonatonotidae Nematocarcinidae Rhynchocinetidae Xiphocarididae Oplophoroidea Oplophoridae Palaemonoidea Anchistioididae Desmocarididae Euryrhynchidae Gnathophyllidae Hymenoceridae Kakaducarididae Palaemonidae Typhlocarididae Pandaloidea Pandalidae Thalassocarididae Pasiphaeoidea Pasiphaeidae Procaridoidea Procarididae Processoidea... Subfamilies and Genera Neophoberinae Acanthacaris Thymopinae Nephropsis Nephropides Thymops Thymopsis Nephropinae Homarus Nephrops Homarinus Metanephrops Eunephrops Thymopides Clawed lobsters comprise a family (Nephropidae, sometimes also Homaridae) of large marine crustaceans. ... Look up Primitive in Wiktionary, the free dictionary The word primitive can refer to: for the art movement, see primitive art and primitivism (art) for the anarchist philosophy, see Anarcho-primitivism for the communist concept, see primitive communism for the baptist church, see primitive baptist primitive (biology) primitive (computer science... The telson is the last division of the body of a crustacean. ...

Discovery

Although apparently widespread, and at least locally common, they were first discovered only in the late nineteenth century when they were dredged up by the Challenger expedition from a depth supposed to be "barren, if not of all life, certainly of animals so high in the scale of existence" (C. S. Bate). Their kinship with the fossil group Eryonoidea, including well-known genera such as Eryon, was immediately recognised. Since Eryon and its relatives were only known from fossils, lastly in the Jurassic, this made the Polychelidae something of a living fossil. Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... The Challenger Expedition was a scientific expedition that made many discoveries to lay the foundation of oceanography. ... The Jurassic period is a major unit of the geologic timescale that extends from about 200 Ma (million years ago) at the end of the Triassic to 146 Ma at the beginning of the Cretaceous. ... Living fossil is a term for any living species (or clade) of organism which closely resembles species otherwise only known from fossils and has no close living relatives. ...

The reason that polychelids remained unknown for so long is that they live on the sea-floor, often at great depths (the family as a whole has a depth range from less than 100 m to over 5,000 m). This also accounts for the lack of eyesight, since almost none of the sun's light penetrates to such abyssal depths. The abyssal zone contains the very deep benthic communities near the bottom of oceans. ...

Larvae

The larvae of polychelids are very distinctive, and were first described under the name Eyoneicus. Over forty different larval forms are known, although few can be ascribed to known adult species. A larva (Latin; plural larvae) is a juvenile form of animal with indirect development, undergoing metamorphosis (for example, insects or amphibians). ...

References

• Galil, B. (2000): Crustacea Decapoda: Review of the genera and species of the family Polychelidae Wood-Mason, 1874. In: A. Crosnier (ed.), Résultats des Campagnes MUSORSTOM, Volume 21, Mémoires du Muséum national d/Histoire naturelle. 184:285-387.

• Ahyong, S. T. and D. E. Brown (2002): New species and new records of Polychelidae from Australia (Crustacea: Decapoda). The Raffles Bulletin of Zoology 50(1): 53-79.