sirenian


Also found in: Dictionary, Thesaurus, Medical, Wikipedia.
Related to sirenian: pinniped, cetacean

sirenian

(sīrē`nēən) or

sea cow,

name for a large aquatic mammal of the order Sirenia. Living sirenians are the dugong and the manatee, both found in warm, shallow waters in sheltered regions, where they feed on seaweeds and seagrasses. Sirenians are the only marine mammals, outside of the whalewhale,
aquatic mammal of the order Cetacea, found in all oceans of the world. Members of this order vary greatly in size and include the largest animals that have ever lived. Cetaceans never leave the water, even to give birth.
..... Click the link for more information.
 order, that spend their entire lives in the water, and they are the only marine mammals that feed exclusively on vegetation. Their heavy, thickset bodies are fishlike in form, the tail ending in a horizontally flattened fin. There are no hind legs, and the forelegs are modified into weak flippers. The gray skin is largely hairless, but there are short bristles (vibrissae) concentrated around the fleshy lips and distributed more sparsely on the body that aid the sense of touch; the upper lip is cleft into two lobes, used for gathering food. The female has a pair of mammary glands on the chest, and holds the pup in her flippers while nursing. It has been speculated that the manatees, which nurse on the water's surface, are the source of mermaidmermaid,
in folklore, sea-dwelling creature commonly represented as having the head and body of a woman and a fishtail instead of legs. Belief in mermaids, and in their counterpart, mermen, has existed since earliest times.
..... Click the link for more information.
 legends.

Manatees

Manatees (genus Trichechus) are found on both sides of the tropical Atlantic Ocean. They are sluggish, largely nocturnal bottom feeders and consume up to 100 lb (45 kg) of vegetation daily. They must surface for air every 15 or 20 min. They are usually 7 to 12 ft (2.1–3.6 m) long and weigh about 500 lb (225 kg), although males sometimes grow much larger. Their paddlelike tail fin is nearly circular. Both parents care for the young, one holding it while the other dives for food. The West Indian manatee, Trichechus manatus, lives in offshore waters, bays, estuaries, and river mouths in Florida, Central America, and the West Indies. It is protected by law in Florida. The Amazonian manatee, T. inunguis, is found in rivers of NE South America, ascending the Amazon as far as Ecuador. Both are listed as endangered species. The West African manatee, T. senegalensis, lives in the coastal rivers and lagoons of W Africa.

Dugongs

The dugong, Dugong dugon, is found in offshore waters of the Red Sea, Indian Ocean, and W South Pacific Ocean. More strictly marine than the manatee, it seldom enters rivers. Its tail fin is crescent-shaped, and the male has long, tusklike incisor teeth. The male may reach a length of 12 ft (3.6 m) and weigh over 600 lb (270 kg). The dugongs' numbers have been depleted by hunting for its flesh, hides, tusks, and oil. The extinct Steller's sea cow was a large northern species that formerly inhabited the Bering Straits. It reached a length of 30 ft (9 m), weighed up to 4 tons (2,400 kg), and was insulated by very thick blubber. When it was discovered by Bering in 1741, the population was very small; within 30 years it was exterminated by hunting.

Evolution and Classification

Although superficially they resemble whales, sirenians have evolved independently. They are descended from the group of ancient land mammals that also gave rise to the elephants. The living sirenians are classified in the phylum ChordataChordata
, phylum of animals having a notochord, or dorsal stiffening rod, as the chief internal skeletal support at some stage of their development. Most chordates are vertebrates (animals with backbones), but the phylum also includes some small marine invertebrate animals.
..... Click the link for more information.
, subphylum Vertebrata, class Mammalia, order Sirenia, families Trichechidae and Dugongidae.

References in periodicals archive ?
The Sirenian Singers will be at Machynlleth Music Club on Saturday, November 8, and on Saturday, November 29, when they will be giving their 30th anniversary gala concert at the William Aston Hall, Wrexham.
The soloists will be Oliver Sammons (baritone) and Judith Sammons (violin), both members of the Sirenian Singers.
On March 14 the Japanese choir will perform with the Sirenian Singers at the Stiwt Theatre in Rhos, near Wrexham.
FLINTSHIRE choir Sirenian Singers have given their first performance at the Symphony Hall, Birmingham.
THE Sirenian Singers' new Christmas CD, Christus Natus has just gone on sale.
THE Sirenian Singers have returned from a successful concert tour of the Berlin and Leipzig areas of Germany.
The Sirenian Singers provided the choir and the soloist was Cecilia Smiga, a finalist in the Welsh Singer of the Year competition.
Tomorrow the Sirenian Singers will perform with Lesley Garrett at the opening concert.
We've got the sensational Catrin Finch in the opening concert with the internationally renowned Sirenian Singers performing the world premier of a new work by my friend Geraint Lewis which even I haven't heard yet - which I'm rather miffed about; a violin and piano recital by two outstanding Russian soloists Dmitri Torchinsky and Elena Nalimova playing works by Rachmaninov, Prokofiev and Ravel amongst others; and An Evening at the Opera starring soprano Helen Field, tenor Nicholas Sales and baritone Jeremy Huw Williams accompanied by Michael Pollock on the old joanna.
THE summer concert season is hotting-up for the Sirenian Singers.
NORTH Wales choir Sirenian Singers had a double win at Freckleton Music Festival in Lancashire.