Basilosauridae


Basilosauridae is a paraphyletic family of extinct cetaceans that lived during the late middle to the early late Eocene, known from all continents including Antarctica. They were probably the first fully aquatic cetaceans.

Taxonomy

Basilosaurinae was proposed as a subfamily containing two genera: Basilosaurus and Basiloterus. They were characterized by elongated distal thoracic vertebrae, lumbar, and proximal sacrococcygeal. All known members of the subfamily are larger than their relatives of the Dorudontinae subfamily except Cynthiacetus. It was declared an invalid subgroup of Basilosauridae by.

Characteristics

Basilosaurids ranged in size from. Like all archaeocetes, they lacked the telescoping skull of modern whales. Their dentition is easily distinguishable from that of other archaeocetes: they lack upper third molars and the upper molars lack protocones, trigon basins, and lingual third roots. The cheek teeth have well-developed accessory denticles.
The hindlimbs are strongly reduced and does not articulate with the vertebral column which lack true sacral vertebrae.
Basilosaurid forelimbs have broad and fan-shaped scapulae attached to a humerus, radius, and ulna which are flattened into a plane to which the elbow joint was restricted, effectively making pronation and supination impossible. Because of a shortage of forelimb fossils from other arachaocetes, it is not known if this arrangement is unique to basilosaurids. Some of the characteristics of basilosaurids are also present in Georgiacetus.

Systematics