- "whole limb" jaws
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Entire third appendage forms jaws. Synapomorphy of the Insecta+Myriapoda.
- wadi
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A shallow, usually sharply defined depression in a desert region, frequently comprising a bed or valley of a stream that is usually dry except during the rainy season and that often forms an oasis.
- warren
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A maze of passageways.
- warty
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A term applied to certain species of wild pigs. The warty pigs are so-called because the adult males typically develop three pairs of warts: on the cheek swellings, on the jaw angle, and above the canine root flanges.
- water vascular system
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A network of ducts filled with water that is used to move echinoderm tentacles and tubefeet via changes in water pressure. Synapomorphy of the Helicoplacopids+Camptostromata+Crinoidea+Asteroidea+Ophiuroidea+Echinoidea+Holothuroidea.
- weaning
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The time when a young animal stops nursing and begins utilizing other food.
- web
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- a structure of delicate, threadlike filaments spun by spiders, some mites, or certain insects;
- a membrane or fold of skin connecting the toes, as of certain amphibians, birds, and mammals;
- the barbs on each side of the shaft of a bird's feather; a vane;
- a latticed or woven structure.
- wetland
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lowland areas satured with water, characterized by low soil oxygen.