Basilosauridae
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Basilosauridae is a family of extinct cetaceans that lived during the middle to late Eocene. Basilosaurids are known from all continents including Antarctica,<ref>Template:Cite journal</ref> and are probably the first fully aquatic cetaceans.<ref name="Uhen-2002">Template:Harvnb</ref><ref name="Buono et.al.2019">Buono M, Fordyce R.E., Marx F.G., Fernández M.S. & Reguero M. (2019). "Eocene Antarctica: a window into the earliest history of modern whales". Advances in Polar Science 30(3): p. 293-302. doi:10.13679/j.advps.2019.0005</ref> The group is noted to be a paraphyletic assemblage of stem group whales<ref name="totalgroup2021">Template:Cite journal</ref> from which the monophyletic Neoceti are derived.<ref name="Davydenko2021">Template:Cite journal</ref>
CharacteristicsEdit
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Basilosaurids ranged in size from Template:Convert and were fairly similar to modern cetaceans in overall body form and function.<ref>Uhen M. (2004). "Form, Function, and Anatomy of Dorudon Atrox (Mammalia, Cetacea): An Archaeocete from the Middle to Late Eocene of Egypt". Papers on Paleontology 34: p. 1-222</ref> Some genera tend to show signs of convergent evolution with mosasaurs by having long serpentine body shape, which suggests that this body plan seems to have been rather successful.<ref>Template:Cite book</ref> 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 archaeocetes, it is not known if this arrangement is unique to basilosaurids, as some of the characteristics are also seen in Georgiacetus.<ref name="Uhen-2002" />
As archaeocetes, basilosaurids lacked the telescoping skull of present whales. Their jaws were powerful,<ref name="Snively_et.al_2015">Snively E, Fahlke J.M. & Welsh R.C. (2015). "Bone-Breaking Bite Force of Basilosaurus isis (Mammalia, Cetacea) from the Late Eocene of Egypt Estimated by Finite Element Analysis". PLOS ONE 10(2): e0118380</ref> with a dentition 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.
Unlike modern whales, basilosaurids possessed small hindlimbs with well defined femur, lower leg and feet. They were, however, very small and did not articulate with the vertebral column, which also lack true sacral vertebrae.<ref name="Uhen-2002" /> While they were unable to support body weight on land, they might have assisted as claspers during copulation.<ref name="Gingerich_et.al._1990">Gingerich P.D., Smith B.H., Simons E.L. (1990). "Hind limbs of eocene basilosaurus: evidence of feet in whales". Science 249(4965): p. 154–157. doi:10.1126/science.249.4965.154</ref> Analysis of tail vertebrate from Basilosaurus and Dorudon indicate they possessed small flukes.<ref name=Gingerich2019>Philip D. Gingerich, Mohammed Sameh M. Antar und Iyad S. Zalmot: "Aegicetus gehennae, a new late Eocene protocetid (Cetacea, Archaeoceti) from Wadi Al Hitan, Egypt, and the transition to tail-powered swimming in whales". PLoS ONE 14(12): e0225391 doi:10.1371/journal.pone.0225391</ref>
TaxonomyEdit
Basilosaurinae was proposed as a subfamily containing two genera: Basilosaurus and Basiloterus.<ref name="Paleodb-42936">Template:Paleodb. Retrieved July 2013.</ref>
SizeEdit
Basilosaurids have a diverse range of sizes. Tutcetus rayanensis, the smallest member, is about 2.51-2.55 meters (8 feet 3 inches - 8 feet 4 inches) long and weighs around 180.4-187.1 kilograms (398-412 pounds).<ref>Template:Cite journal</ref> On the other hand, Basilosaurus cetoides is impressively long, reaching approximately 18 meters.<ref>Template:Cite journal</ref> The largest known basilosaurid, Perucetus colossus, is believed to be even bigger, with a length of about Template:Convert and possibly comparable to, if not larger than, the modern blue whale in terms of weight,<ref>Template:Cite journal</ref> though other researchers argue that it was much lighter.<ref>Template:Cite journal</ref><ref>Template:Cite news</ref>
SystematicsEdit
- Family Basilosauridae
- Subfamily Basilosaurinae
- Genus Basilosaurus
- Genus Basiloterus
- Subfamily Dorudontinae
- Genus Ancalecetus
- Genus Chrysocetus
- Genus Cynthiacetus
- Genus Dorudon
- Genus Masracetus
- Genus Ocucajea
- Genus Saghacetus
- Genus Stromerius
- Genus Supayacetus
- Genus Zygorhiza
- Subfamily Pachycetinae
- Genus Pachycetus
- Genus Antaecetus