Basilosauridae

Basilosauridae Temporal range: Late Eocene
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Saghacetus osiris
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Cetacea
Suborder:	Archaeoceti
Family:	Basilosauridae Cope 1868
Genera
See text

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 Uhen 2013.

Characteristics

File:Dorudon atrox2.jpg

Dorudon atrox skeleton

Basilosaurids ranged in size from 4 to 16 m (13 to 52 ft). 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.

Taxonomy

• Family Basilosauridae
  • Subfamily Basilosaurinae
    • Genus Basilosaurus
    • Genus Basiloterus
    • Genus Basilotritus
    • Genus Eocetus
    • Genus Platyosphys
  • Subfamily Dorudontinae
    • Genus Ancalecetus
    • Genus Chrysocetus
    • Genus Cynthiacetus
    • Genus Dorudon
    • Genus Ocucajea
    • Genus Stromerius
    • Genus Supayacetus
    • Genus Saghacetus
    • Genus Zygorhiza
  • Subfamily Stromeriinae
    • Genus Stromerius

See also

• Evolution of cetaceans
• Leviathan