Ornithorhynchidaeplatypus

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This family consists of a single genus and species, the duck-billed platypus. Often considered the most unique and bizarre of mammals, the duck-billed platypus uses receptors sensitive both to tactile stimulation and weak electrical fields to sense prey when digging under water. These sense organs are located in its "bill." This species is highly aquatic. It has webbed feet; dense, woolly, water-repellant fur; and furrows along the sides of its head to protect the eyes and ears when it swims under water. The external opening for the ear is tubular and the ears lack pinnae.

The bill of a platypus is soft, flexible, and leathery, unlike a bird's beak. Nostrils are located at its tip. While young platypuses have molars, adults are toothless. They grind their food between horny (keratinous) plates located over the gums.

Young platypuses have teeth, but these are lost in adults. Food is masticated between horny plates located on each jaw. The anterior part of these plates is ridged and is used to chop food; the posterior part is expanded and flat and used for crushing.

Male platypuses have a sharp spur attached to each ankle. The spurs are grooved and connected to venom glands; these weapons may be used in combat between males for mates.

A platypus feeds primarily on aquatic crustaceans, insect larvae, and some plants.

Duck-billed platypuses live in burrows along the banks of water, including lakes, rivers, and even mountain streams. They have well-developed claws, but these are not as large as the claws of echidnas. Platypuses are excellent diggers. When a female is about to lay her eggs, she builds a deep burrow (which may be as much as 20-30 m in length), plugs the entrance, and incubates the eggs for 10-12 days. There is no pouch, and the mother curls her body around the eggs to keep them warm. Young are nursed for about five months.

References and literature cited

Feldhamer, G. A., L. C. Drickamer, S. H. Vessey, and J. F. Merritt. 1999. Mammalogy. Adaptation, Diversity, and Ecology. WCB McGraw-Hill, Boston. xii+563pp.

Marshall, L. G. 1984. Monotremes and marsupials. Pp. 59-115 in Anderson, S. and J. Knox Jones, Jr., eds. Orders and Families of Recent Mammals of the World. John Wiley & Sons, New York. xii+686 pp.

Vaughan, T. A. 1986. Mammalogy. Third Edition. Saunders College Publishing, Fort Worth. vi+576 pp.

Vaughan, T. A., J. M. Ryan, N. J. Czaplewski. 2000. Mammalogy. Fourth Edition. Saunders College Publishing, Philadelphia. vii+565pp.

Contributors

Anna Bess Sorin (author), Biology Dept., University of Memphis, Phil Myers (author), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

motile

having the capacity to move from one place to another.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate