Bone histology of the ribs of the archaeocetes (Mammalia: Cetacea)

Histological study of the ribs in two archaeocetes, Basilosaurus cetoides and Zygorhiza kochii, reveals conspicuous pachyostosis, with hyperostosis of periosteal cortices and absence of a free medullary cavity. In addition, abundant remains of calcified cartilage matrix, associated with extensive globular ossification, exist within the medulla. Among Cetacea, these features seem to be unique to the archaeocetes. Conversely, the structural...