Basiloterus

Abstract: Two new basilosaurid archaeocetes are described from middle Eocene (Bartonian) green shales in the middle part of the Drazinda Formation in the Sulaiman Range of southwestern Punjab. Basilosaurus drazindai, sp. nov., has a lumbar vertebra with a centrum the size and shape of those of later Basilosaurus, but this differs in having an anteroposteriorly longer neural arch and neural spine, and in having more anteriorly-projecting metapophyses. Basiloterus hussaini, gen. et sp. nov., is smaller than Basilosaurus and has lumbar centra a little less elongated than those of Basilosaurus. Discovery of Basilosaurus and more careful documentation of lithological changes lead us to reinterpret previous correlation of Sulairnan Range Eocene formations to the geological time scale using the global record of eustatic sea-level change. The Habib Rahi, Domanda, Pir Koh, and Drazinda Formations now appear to span almost all of Lutetian, Bartonian, and Priabonian time. These formations can be traced for long distances parallel to the margin of the Indo-Pakistan subcontinent, they contain little silt and little or no sand, and they appear to have been deposited offshore on a passive continental margin that was remarkably stable through middle and late Eocene time.