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Jaw Animals: Micrognathozoa

Conservation Status

Jaw animals are not considered threatened or endangered.


In Greenland jaw animals have been found only in cold springs that often are frozen for seven to eight months of the year. The island where they live has more than one thousand springs that maintain a constant temperature throughout the year and therefore run during the winter, but the jaw animals avoid this kind of spring. This finding suggests that the deep-freeze period is important for this animal's life cycle.


Jaw animals appear to be very choosy about what they eat. If by accident a jaw animal grabs and swallows an unwanted food, it quickly rejects it. Using a characteristic "vomit behavior," the animal lifts its forehead to a vertical position, pushes its entire jaw out of its mouth, and ejects the unwanted food.



Ruppert, Edward E., Richard S. Fox, and Robert D. Barnes. Invertebrate Zoology. 7th ed. Belmont, CA: Thomson-Brooks/Cole, 2004.

When they move, jaw animals either crawl or swim. While swimming, they move slowly in a spiral. When crawling, they glide slowly on the bottom. (Illustration by Emily Damstra. Reproduced by permission.)

Web sites:

"Jaws: New Animal Discovered." Science Now. http://www.calacademy.org/science_now/archive/headline_science/new_critter_120700.htm (accessed on February 20, 2005).

"Micrognathozoa: A New Microscopic Animal Group from Greenland." Zoological Museum in Copenhagen. http://www.zmuc.dk/InverWeb/Dyr/Limnognathia/Limno_intro_UK.htm (accessed on February 20, 2005).

Additional topics

Animal Life ResourceJellyfish, Sponges, and Other Simple AnimalsJaw Animals: Micrognathozoa - Physical Characteristics, Behavior And Reproduction, Conservation Status - GEOGRAPHIC RANGE, HABITAT, DIET, JAW ANIMALS AND PEOPLE