430 -418 million years ago
Many of the changes of the nervous and endocrine systems in ancestral sarcopterygians are shared by tetrapods. These changes included a modified cerebrum, a cochlea homolog involved in sound perception, and novel neuropeptides and hormones.
A number of changes evolved in the nervous systems of the sarcopterygian ancestors of tetrapods. The hippocampus modified its position to be located along the medial and dorsomedial wall of the evaginated cerebral hemisphere (Hassler, p. 117). The fornix connected hippocampus and septal region (Hassler, p. 122). The olfactory tubercle possessed the same subdivisions as observed in mammals (Hassler, p. 122). These fish also evolved paleostriatal and nestriatal areas homologous to those in tetrapods (Hassler, p. 127). The lagena from the vestibule functioned in the perception of sound. Autonomic fibers traveled only through the ventral roots of spinal nerves.
Some of the modifications of sarcopterygian hormones and neuropeptides
were conserved in tetrapods such as changes in neurohypophysial hormone
sequences (Shinohara-Ohtani, 1998), the -MSH sequence in the POMC gene
(Lee, 1999), and structural changes of ultimobranchial body (Shinohara-Ohtani,
1998). The distribution of neuropeptide Y, -MSH, and ANF recognition sites
in the brains of lungfish is similar to that observed in amphibians. The
distribution of FMRF-amide in lungfish brains is more similar to amphibians
than other fish (Vallarino, 1998). A duplication of the proenkalphin gene
produced prodynorphin in the lineage which produced sarcopterygians and
tetrapods (Danielson, 1999). The distribution of -MSH recognition sites
in the brains of lungfish is similar to that observed in amphibians (Vallarino,