Acrania

1 definition found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  Acrania \A*cra"ni*a\, n. [NL., from Gr. 'a priv. + ? skull.]
     1. (Physiol.) Partial or total absence of the skull.
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     2. pl. (Zool.) The lowest group of Vertebrata, including the
        amphioxus, in which no skull exists.


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