| Whenever muscular control of the operculum was established, it was probably based on the cleithrum. |
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| The tetrapodomorph scapulocoracoid is typically a relatively slight, tripodal structure on the inner surface of the cleithrum. |
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| The glenoid fossa itself is somewhat pear-shaped, with the small end pointing toward the cleithrum. |
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| The pectoral fin is set low on the lateral flank behind the notch of the cleithrum and is supported by a small rounded lobe covered with minute rhombic scales. |
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| The third series begins at the bases of the first branchiostegal rays and extends posteriorly to the cleithrum. |
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| The cleithrum, 17th most abundant, is underrepresented in comparison with many cranial bones, but outnumbers others such as the sphenotic, ethmoid, otolith and preopercular. |
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| In Ichthyostega, Acanthostega, and also in Hynerpeton and Ventastega, the cleithrum was relatively reduced, though it was still a substantial dorsally extensive blade. |
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