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Crown group - Wikipedia, the free encyclopedia (593 words) |
 | Stem and crown groups are hierarchical; thus, an extinct crown-group bird may lie in the stem group of a subset of the birds, such as the passerines; and stem-group birds lie, together with crown group birds and crocodiles and several extinct groups, in the crown group of the Archosauria. |
| A crown group and its stem group considered together are known as the total group. |
| Stem group organisms always lack one or more features that are present at the base of the crown group to which they are attached. |
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