Unique Vertebral Morphology of the Archaeocete Cetacean Basilosaurus Cetoides and its Implications for Swimming Funtion
Basilosaurid cetaceans are a family of highly derived archaeocete whales that were the first to become adapted to an obligate aquatic lifestyle during the secondary radiation of cetaceans to water from a terrestrial environment. Basilosaurine basilosaurids represent a subfamily with a serpentine-like body shape. The taxon Basilosaurus cetoides from the Middle to-Late Eocene is best known for its extremely elongated vertebrae that aid in producing a lengthened, fusiform body. However, no consensus has emerged with regard to its specific form of locomotion. Other clades of obligate marine vertebrates having an elongated body are characterized as anguilliform swimmers, utilizing an undulatory wave of large amplitude that travels through most of the body. A comparative analysis of Basilosaurus cetoides with other extinct and extant cetacean taxa reveals structurally adapted vertebrae in B. cetoides for increased flexibility. Here, Basilosaurus cetoides is categorized as an anguilliform swimmer utilizing ambush methods of predation.