Basilosauridae

Basilosauridae is a paraphyletic family of extinct cetaceans that lived during the late middle to the early late Eocene,[2] known from all continents including Antarctica.[1][3] They were probably the first fully aquatic cetaceans.[2]

Basilosauridae Temporal range: Late Eocene, 45–33.9 Ma PreꞒ Ꞓ O S D C P T J K Pg N [1]
Saghacetus osiris
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Artiodactyla
Infraorder:	Cetacea
Family:	†Basilosauridae Cope 1868[1]
Genera
See text

Taxonomy

Basilosaurinae was proposed as a subfamily containing two genera: Basilosaurus and Basiloterus.[4] 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.[5] It was declared an invalid subgroup of Basilosauridae by Uhen 2013 harvnb error: no target: CITEREFUhen2013 (help).[4]

Characteristics

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.[2]

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.[2]The overall long serpentine body shape of Basilosaurids show signs of convergent evolution with mosasaurs which suggests that this body plan seems to have been rather successful.[6]

Systematics

• 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

See also

• Evolution of cetaceans
• Leviathan

Notes

1. Basilosauridae in the Paleobiology Database
2. Uhen 2002
3. Fostowicz-Frelik 2003
4. Basilosauridae in the Paleobiology Database. Retrieved July 2013.
5. Uhen 2008 harvnb error: no target: CITEREFUhen2008 (help)
6. Oceans of Kansas: a Natural History of the Western Interior Sea. Indiana University Press. ISBN 9780253345479.

References

• Cope, Edward Drinker (1868). "An addition to the vertebrate fauna of the Miocene period, with a synopsis of the extinct Cetacea of the United States". Proceedings of the Academy of Natural Sciences of Philadelphia. 19 (4): 138–57. JSTOR 4059641. OCLC 4909181381.CS1 maint: ref=harv (link)
• Fostowicz-Frelik, Łucja (2003). "An enigmatic whale tooth from the Upper Eocene of Seymour Island, Antarctica" (PDF). Polish Polar Research. 24 (1): 13–28. doi:10.1002/jmor.20075. PMID 22965565. Retrieved September 2013. Check date values in: |accessdate= (help)CS1 maint: ref=harv (link)
• Gingerich, Philip D (2007). "Stromerius nidensis, new archaeocete (Mammalia, Cetacea) from the Upper Eocene Qasr El-Sagha Formation, Fayum, Egypt" (PDF). Contributions from the Museum of Paleontology. 31 (13): 363–78. OCLC 214233870. Retrieved February 2013. Check date values in: |accessdate= (help)CS1 maint: ref=harv (link)
• Uhen, Mark D (2002). "Basilosaurids". In Perrin, William R; Wiirsig, Bernd; Thewissen, J G M (eds.). Encyclopedia of Marine Mammals. Academic Press. pp. 78–81. ISBN 978-0-12-551340-1.CS1 maint: ref=harv (link)