- ulna
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One of the two distal bones in the forelimb of tetrapods. Synapomorphy of tetrapods+Euthenopteron
- ultrasound
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uses sound above the range of human hearing for either navigation or communication or both
- understory
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The layer of shrubs, herbs and small trees beneath the forest canopy.
- ungulate
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A hoofed mammal which is usually adapted for running. Includes deer, cattle, gazelles, horses, elephants, and hyraxes. Most are large herbivores. The term no longer has taxonomic significance.
- urban
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living in cities and large towns, landscapes dominated by human structures and activity.