Topic summary
Aïstopods
Extracted from the Wikipedia article Aistopoda.
A recent paper described the internal organization of the aistopod head, finding that aïstopods retained many fish-like features of the skull and brain, including a persistent extension of the notochord into the head and an open canal between the pituitary gland and the mouth. Because these features are lost early in tetrapod evolution, this may be evidence that aistopods diverged from other tetrapods soon after the origin of digits.