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EZ EZ
wrote...
6 years ago
Nowadays we consider lungfishes to be more closely related to tetrapods than the coelacanths are, but in earlier times coelacanths were thought to be the more closely related forms.
 
  How have changes in our way of thinking about phylogenetic relationships changed our opinion in this case?
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wrote...
6 years ago
Lungfishes have many of their own derived features (e.g., the pattern of bones on the dermal skull roof) that appeared to debar them from direct ancestry of tetrapods, whereas the coelacanths lacked specialized characters and seemed to have more tetrapod-like features. However, we now no longer look for ancestors but for sister-group relationships based on shared derived characters. Lungfishes share derived features with tetrapods that are absent from coelacanths. In contrast, the ways in which coelacanths appear more similar to tetrapods are actually ancestral sarcopterygian features, not indicative of a close relationship.
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