The genus Cynthiacetus occurs in Bartonian and Priabonian sediments of the Southeastern United States and Peru. This is a larger animal with skull comparable to the two meter skull of later basilosaurids, but it lived before the emergence of Basilosaurus cetoides.
Cynthiacetus also possessed elongated thoracic, lumbar (middle back) and forward caudal (tail) vertebrae. Cynthiacetus maxwelli is known from Alabama, Florida, Georgia, North Carolina, and Mississippi.
Only the North Carolina specimen has been tentatively dated to the Bartonian. The vertebrae of Cynthiacetus are generally large but lack the elongations seen in other basilosaurids, especially later genre. To date, we have no hip, leg or tail material available for Cynthiacetus.
A Review of North American Basilosauridae: Mark D. Uhen, 2013. Bulletin 31, Vol. 2, Alabama Museum of Natural History, April,1, 2013