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DEVONIAN PERIOD

416-359 million years ago

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fish


The common ancestor of Panderichthys and tetrapods evolved the rudiments of ribs. The shoulder differed from that of tetrapods in that the glenoid cavity was smaller and more medial and the scapulocoracoid was bigger. The ulna had increased in size in these fish and was intermediate between earlier fish and tetrapods. The fin rays were still composed of dermal bone, unlike the endochondral bone which would compose tetrapod digits (Clark, 2002). The fin of Panderichthys is depicted below with bones homologous to those of tetrapods (such as the huerus in blue, radius in red, and ulna in green).

fin bones