Posidonia

Posidonia
Posidonia oceanica
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Monocots
Order:	Alismatales
Family:	Posidoniaceae Hutch.
Genus:	Posidonia K.D.Koenig
Species
See text.
Posidonia distribution range

External identifiers for Posidonia
Encyclopedia of Life	101673
ITIS	39059
NCBI	55487
WoRMS	144232
Also found in: , NPGS/GRIN

See text.

Posidonia is a genus of flowering plants. It contains nine species of marine plants ("seagrass"), found in the seas of the Mediterranean and around the south coast of Australia.

The APG system (1998) and APG II system (2003) accept this genus as constituting the sole genus in the family Posidoniaceae, which it places in the order Alismatales, in the clade monocots. The AP-Website concludes that the three families Cymodoceaceae, Posidoniaceae and Ruppiaceae form a monophyletic group. Earlier systems classified this genus in the family Potamogetonaceae or in the family Posidoniaceae but belonging to order Zosterales.

This is a list of species that are contained by the genus:

The species described by Linnaeus, Posidonia oceanica, is found in the Mediterranean; the rest are located around the southern coast of Australia. Some species are endemic seagrasses of Western Australia, all the Australian species are found in that region's diverse habitats. This arrangement was divided into two complexes: the Posidonia australis and Posidonia ostenfeldii groups. Some species descriptions may only be regional characteristics, and may need further revision.

In 2006 a huge clonal colony of P. oceanica was discovered south of the island of Ibiza. At 8 km across and possibly up to 100,000 years of age, it may be one of the largest and oldest clonal colonies on Earth.

Marine grasses families: Zosteraceae, Cymodoceaceae, Ruppiaceae and Posidoniaceae. Related families: Potamogetonaceae and (and sometimes including) Zannichelliaceae.

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