View source for Basilosaurus

{{short description|Prehistoric cetacean genus from the Late Eocene epoch}}
{{Use dmy dates|date=January 2025}}
{{Automatic taxobox
| name = ''Basilosaurus''
| fossil_range = [[Eocene]] ([[Bartonian]] to [[Priabonian]]), {{Fossil range|41.3|33.9}}<ref>{{cite web |title=Dir Abu Lifa (Eocene of Egypt) |url=https://paleobiodb.org/classic/basicCollectionSearch?collection_no=40516&is_real_user=1 |website=PBDB |publisher=Mark Uhen |access-date=14 May 2019 |archive-date=18 July 2020 |archive-url=https://web.archive.org/web/20200718085053/https://www.paleobiodb.org/classic/basicCollectionSearch?collection_no=40516&is_real_user=1 |url-status=live }}</ref>
| image = Basilosaurus cetoides (1).jpg
| image_upright = 1.15
| image_caption = ''B. cetoides'' skeleton, [[National Museum of Natural History]], [[Washington DC]]
| taxon = Basilosaurus
| authority = {{Harvnb|Harlan|1834}}
| subdivision_ranks = Species
| subdivision = * ''B. cetoides'' ([[Type species|type]])<br /><small>{{Harvnb|Owen|1839}}</small>
* ''B. isis''<br /><small>{{Harvnb|Andrews|1904}}</small>
| synonyms = * ''Zeuglodon''<br /><small>{{Harvnb|Owen|1839}}</small>
* ''Hydrarchos''?<br /><small>{{Harvnb|Koch|1845}}</small>
* ''Alabamornis''<br /><small>{{Harvnb|Abel|1906}}</small>
}}

'''''Basilosaurus''''' (meaning "king lizard") is a [[genus]] of large, predatory, prehistoric [[Archaeoceti|archaeocete]] whale from the late [[Eocene]], approximately 41.3 to 33.9 [[mya (unit)|million years ago]] (mya). First described in 1834, it was the first archaeocete and prehistoric whale known to science.<ref name="Uhen-20022"/> Fossils attributed to the [[type species]] ''B. cetoides'' were discovered in the southeastern [[United States]]. The generic name, meaning "king lizard", was given due to the initial misconception about the fossil material as that of a giant reptile. The animal was later found to be an early [[marine mammal]], prompting attempts at renaming the creature, which failed as the [[International Code of Zoological Nomenclature#Principle of priority|rules of zoological nomenclature]] dictate using the original name given. The second species named in 1904, ''B. isis'', lived in the region currently known as the [[Mediterranean Sea]], with fossils found in [[North Africa]] and [[Jordan]].

''Basilosaurus'' is thought to have been one of the largest animals of the [[Paleogene]], with the type species ''B. cetoides'' measuring around {{convert|17|-|20|m|ft}} long and weighing up to {{convert|15|MT|ST}}. It was the top predator of its environment in the shallows of the inland sea, preying on sharks, large fish and other marine mammals. The smaller dolphin-like relative ''[[Dorudon]]'' seems to have been the predominant food source of ''Basilosaurus'' based on its stomach contents and the bite marks preserved in the skull of ''Dorudon''.

''Basilosaurus'' was at one point a [[wastebasket taxon]] before the genus slowly started being reevaluated, with many species of different Eocene cetacean being assigned to the genus in the past. However, most are invalid or have been reclassified under a new or different genus, leaving only two confirmed species.
''Basilosaurus'' may have been one of the first fully aquatic cetaceans,<ref name="Uhen-20022">{{Cite book | last = Uhen | first = Mark D. | chapter = Basilosaurids | pages = [https://archive.org/details/encyclopediaofma2002unse/page/79 79–81] | title = Encyclopedia of Marine Mammals | editor1-last = Perrin | editor1-first = William F. | editor2-last = Würsig | editor2-first = Bernd | editor3-last = Thewissen | editor3-first = J. G. M. | year = 2002 | publisher = Academic Press | isbn = 978-0-12-551340-1 | chapter-url = https://archive.org/details/encyclopediaofma2002unse/page/79 }}</ref> sometimes referred to as the Pelagiceti.<ref>{{cite web |title=Clade Pelagiceti Uhen 2008 (whale) |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=134057&is_real_user=1 |website=PBDB}}</ref> ''Basilosaurus'', unlike modern cetaceans, had various types of teeth–such as [[canine tooth|canines]] and [[molar (tooth)|molar]]s–in its mouth ([[heterodonty]]), and it probably was able to chew its food, in contrast to modern cetaceans which swallow their food whole.<ref>{{cite web |title=HOW DOES DIGESTION TAKE PLACE IN WHALES? |url=https://baleinesendirect.org/en/how-does-digestion-take-place-in-whales/ |website=Whales, online|date=15 July 2015 }}</ref><ref>{{cite web |title=Basilosaurus the Bone-Crusher |url=https://www.nationalgeographic.com/science/phenomena/2015/03/06/basilosaurus-the-bone-crusher/ |archive-url=https://web.archive.org/web/20190807213408/https://www.nationalgeographic.com/science/phenomena/2015/03/06/basilosaurus-the-bone-crusher/ |archive-date=7 August 2019 |website=National geographic|date=6 March 2015 }}</ref>

== Taxonomic history ==
=== Etymology ===
[[File:Basilosaurus by Knight.jpg|thumb|Outdated restoration of ''Basilosaurus'' by [[Charles R. Knight]] from 1907 showing a serpent-like body-plan]]
The two species of ''Basilosaurus'' are ''B. cetoides'', whose remains were discovered in the United States, and ''B. isis'', which was discovered in Egypt. ''B. cetoides'' is the [[type species]] for the genus.<ref name=zalmout2000>{{Cite journal| last1 = Zalmout | first1 = I. S.| last2 = Mustafa | first2 = H. A.| last3 = Gingerich | first3 = P. D.| title = Priabonian ''Basilosaurus isis'' (Cetacea) from the Wadi Esh-Shallala Formation: first marine mammal from the Eocene of Jordan| year = 2000 | journal = Journal of Vertebrate Paleontology | volume = 20 | issue = 1 | pages = 201–204| url = https://www.researchgate.net/publication/232663337| oclc = 4908948040 | doi=10.1671/0272-4634(2000)020[0201:pbicft]2.0.co;2| s2cid = 130179065}}</ref><ref name="bbc">{{cite web | title = Basilosaurus | publisher = BBC Nature | url = http://www.bbc.co.uk/science/seamonsters/factfiles/basilosaurus.shtml | access-date = 24 August 2013 | archive-date = 21 September 2010 | archive-url = https://web.archive.org/web/20100921083651/http://www.bbc.co.uk/science/seamonsters/factfiles/basilosaurus.shtml }}</ref> The [[holotype]] of ''B. cetoides'' was found in [[Ouachita Parish]], [[Louisiana]].{{sfn|Harlan|1834}}<ref>{{cite web |title=Bry Plantation (Eocene of the United States) |url=https://paleobiodb.org/classic/basicCollectionSearch?collection_no=32907 |website=PBDB}}</ref> The exact formation is said to be the [[Yazoo Clay]]/formation.<ref>{{Cite web |title=Ouachita River (Eocene of the United States) |url=https://paleobiodb.org/classic/basicCollectionSearch?collection_no=75638&is_real_user=1 |website=PBDB.org}}</ref> Vertebrae were sent to the [[American Philosophical Society]] by a Judge Henry Bry of [[Ouachita Parish, Louisiana]] and Judge John Creagh of [[Clarke County, Alabama|Clarke County]], [[Alabama]]. Both fossils ended up in the hands of the anatomist [[Richard Harlan]], who requested more examples from Creagh.<ref name=Switek>{{cite web| last = Switek | first = Brian| title = The Legacy of the ''Basilosaurus'' | publisher = ScienceBlogs| url = http://scienceblogs.com/laelaps/2008/09/21/the-legacy-of-the-basilosaurus/| date = 21 September 2008 | access-date = 14 September 2013}}</ref><ref>{{cite web|url=http://www.smithsonianmag.com/science-nature/how-did-whales-evolve-73276956/?all |title=How Did Whales Evolve? |author=Brian Switek |work=[[Smithsonian (magazine)|Smithsonian]] |date=December 2010 }}</ref> The first bones were unearthed when rain caused a hillside full of sea shells to slide. The bones were lying in a curved line "measuring upwards of four hundred feet [122 meters] in length, with intervals which were vacant." Many of these bones were used as [[andiron]]s and destroyed; Bry saved the bones he could find, but was convinced more bones were still to be found on the location. Bry speculated that the bones must have belonged to a "sea monster" and supplied "a piece having the appearance of a tooth" to help determine which kind.<ref>{{Harvnb|Harlan|1834|p=400}}</ref>

Harlan identified the tooth as a [[Pinna (genus)|wedge-shaped shell]] and instead focused on "a vertebra of enormous dimensions" which he assumed belonged to the order "[[Marine reptile|Enalio-Sauri]] of [[William Conybeare (geologist)|Conybeare]]", "found only in the sub-cretaceous series."<ref>{{Harvnb|Harlan|1834|p=401}}</ref> He noted that some parts of the vertebra were similar to those of ''[[Plesiosaurus]]'' and skull was similar to ''[[Mosasaurus]]'', but that they were completely different in proportions. Comparing his vertebra to those of large dinosaurs such as ''[[Megalosaurus]]'' and ''[[Iguanodon]]'', Harlan concluded that his specimen was considerably larger—he estimated the animal to have been no less than {{Convert|80|–|100|ft|m|abbr=on}} long—and therefore suggested the name ''Basilosaurus'', meaning "king lizard".<ref>{{Harvnb|Harlan|1834|pp=402–403}}</ref>

Harlan brought his assembled specimens (including fragments of jaw and teeth, humerus, and rib fragments) to the UK where he presented them to anatomist [[Richard Owen]]. Owen concluded that the molar teeth were two-rooted, a dental morphology unknown in fishes and reptiles, and more complex and varied than in any known reptile, and therefore that the specimen must be a mammal. Owen correctly associated the teeth with cetaceans, but he thought it was an herbivorous animal, similar to [[sirenia]]ns.<ref>{{Harvnb|Owen|1839|pp=72–73}}</ref> Consequently, Owen proposed renaming the find ''Zeuglodon cetoides'' ("whale-like [[yoke]] teeth" in reference to the double-rooted teeth) and Harlan agreed.<ref name="Owen-1939-p75">{{Harvnb|Owen|1839|p=75}}</ref>

===Wadi El Hitan===
{{Main|Wadi El Hitan}}
[[File:Wadi Al-Hitan.jpg|thumb|Skeleton of ''B. isis'' at [[Wadi El Hitan]]]]
[[File:Basilosaurus isis fossil, Nantes History Museum 03.jpg|thumb|left|''Basilosaurus isis'' fossil, Nantes History Museum in France]]
Wādī al-Ḥītān ({{Langx|ar|وادي الحيتان|translit=|lit=Valley of the Whales}}) is an Egyptian sandstone formation where many early-whale skeletons were discovered.<ref>{{cite web|url=http://www.worldheritagesite.org/list/id/1186|title=Wadi Al-Hitan| publisher=World Heritage Site|access-date=17 August 2017}}</ref> German botanist [[Georg August Schweinfurth]] discovered the first archaeocete whale in Egypt (''Zeuglodon osiris'', now ''[[Saghacetus]] osiris'') in 1879. He visited the [[Qasr el Sagha Formation]] in 1884 and 1886 and missed the now famous Wadi El Hitan by a few kilometers. German paleontologist [[Wilhelm Dames|Wilhelm Barnim Dames]] described the material, including the type specimen of ''Z. osiris'', a well-preserved dentary.<ref name=gingerich2007>{{cite book |last=Gingerich |first=P. D. |year=2008 |chapter-url=http://www-personal.umich.edu/~gingeric/PDFfiles/PDG471_WhalesinEgypt.pdf |title=Elwyn Simons: A Search for Origins |chapter=Early Evolution of Whales: A Century of Research in Egypt |series=Developments in Primatology: Progress and Prospects |pages=107–124 |editor1-last=Fleagle |editor1-first=J. G. |editor2-last=Gilbert |editor2-first=C. C. |location=Berlin |publisher=Springer |isbn=978-0-387-73895-6 |access-date=31 August 2013 |archive-date=5 November 2018 |archive-url=https://web.archive.org/web/20181105101205/http://www-personal.umich.edu/~gingeric/PDFfiles/PDG471_WhalesinEgypt.pdf |url-status=live }}</ref>

Hugh Beadnell, head of the Geological Survey of Egypt 1896–1906,<ref name=gingerich2007/> named and described ''Zeuglodon isis'' in {{Harvnb|Andrews|1904}} based on a partial mandible and several vertebrae from Wadi El Hitan in Egypt.<ref>{{Harvnb|Andrews|1904|pp=214–215}}</ref> {{Harvnb|Andrews|1906}}<ref>{{Harvnb|Andrews|1906|pp=255}}</ref> described a skull and some vertebrae of a smaller archaeocete and named it ''Prozeuglodon atrox'', now known today as ''[[Dorudon]] atrox''. {{Harvnb|Kellogg|1936}} discovered deciduous teeth in this skull and it was then believed to be a juvenile [''Pro'']''zeuglodon isis'' for decades before more complete fossils of mature ''Dorudon'' were discovered.{{sfn|Kellogg|1936|p=81}}<ref name=gingerich2007/><ref>{{Cite journal| last = Uhen | first = Mark D.| title = Form, Function, and Anatomy of ''Dorudon Atrox'' (Mammalia, Cetacea): An Archaeocete from the Middle to Late Eocene of Egypt| year = 2004 | journal = Papers on Paleontology | volume = 34 |page=11| hdl = 2027.42/41255}}</ref>

In the 1980s, [[Elwyn L. Simons]] and [[Philip D. Gingerich]] started to excavate at Qasr el-Sagha and Wadi El Hitan with the hope of finding material that could match archaeocete fossils from Pakistan. Since then, over 500 archaeocete skeletons have been found at these two locations, of which most are ''B. isis'' or ''D. atrox'', several of the latter carrying bite marks assumed to be from the former.<ref name=gingerich2007/> A 1990 paper described additional fossils including foot bones and speculated that the reduced hind limbs were used as copulatory guides.<ref name="pmid-17836967"/> One thing that was noted, was that whale fossils were so common, that when a mason company looked at their newest table counter, they realized that they had created a cross section of a 40 million year old basilosaurid fossil. This find was another thing that caught the eye of Gingerich.<ref>{{cite web |title=Fossil Found in Kitchen Counter |url=https://cms.video.nationalgeographic.com/video/news/wild-chronicles/00000144-0a1e-d3cb-a96c-7b1fd7a10000?gc=%2Fvideo%2Fenvironment%2Fenvironmental-threats&gs=picks |website=National Geographic }}{{Dead link|date=August 2025 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

In 2015, a complete skeleton, the first-ever such find for ''Basilosaurus'', was uncovered in Wadi El Hitan, preserved with the remains of its prey, including a ''Dorudon'' and several species of fish. The whale's skeleton also shows signs of scavenging by large sharks such as the [[Otodontidae|otodontid]] ''[[Otodus sokolovi]]'', though the study considered it possible that this shark was also part of the diet of ''Basilosaurus''.<ref name="Basilo2019"/>

===Wastebasket taxa===
Many dubious species have been assigned to ''Basilosaurus'' in the past which have since been invalidated or were too incomplete to determine anything.

====''Nomina dubia''====
A ''[[nomen dubium]]'' is a scientific name that is of unknown or doubtful application. There are a few documented cases of this being applied to ''Basilosaurus'' in the past.
[[Image:Hydrarchos.jpg|thumb|Albert Koch's "Hydrarchos" fossil skeleton from 1845, two ''Basilosaurus'' or ''Pontogeneus'' skeletons tied together which was presented as the bones of an ancient sea monster. The skeleton was destroyed during the [[Great Chicago Fire]] in 1871.]]
* ''Zeuglodon wanklyni'', was a supposed species of ''Basilosaurus'', that described in 1876 based on a skull found in the Wanklyn's Barton Cliff in the United Kingdom. This single specimen, however, quickly disappeared and has since been declared a ''[[nomen nudum]]'' or referred to as ''[[Zygorhiza]] wanklyni''.<ref>{{Paleodb|63087|Basilosauridae}}: Taxonomic history. Retrieved August 2013.</ref>
* ''Zeuglodon vredense'' or ''vredensis'' was named in the 19th century based on a single, isolated tooth without any kind of accompanying description, and {{Harvnb|Kellogg|1936}} therefore declared it a ''nomen nudum''.{{sfn |Kellogg|1936|p=264}}<ref>{{Paleodb|63141|Zeuglodon vredense (nomen nudum)}}. Retrieved August 2013.</ref>
* ''Zeuglodon puschi[i]'' was a species that was said to come from Poland, it was named by {{Harvnb|Brandt|1873}}. {{Harvnb|Kellogg|1936}} noted that the species is based on an incomplete vertebra of indeterminable position and, therefore, that the species is invalid.{{sfn|Kellogg|1936|p=263}}<ref>{{Paleodb|63140|Zeuglodon puschii (nomen dubium)}}. Retrieved August 2013.</ref>
* ''Zeuglodon brachyspondylus'' was described by [[Johannes Peter Müller]] based on some vertebrae from "''Zeuglodon hydrarchus''",<ref>{{Cite book| last = Müller | first = Johannes Peter | author-link = Johannes Peter Müller| title = Über die fossilen Reste der Zeuglodonten von Nordamerika mit Rücksicht auf die europäischen Reste aus dieser Familie| year = 1849 | pages = 1–38 | publisher = Reiner | location = Berlin | oclc = 422134028}}
*{{cite web |date= |title= Über die fossilen Reste der Zeuglodonten von Nordamerica|website=pbdb.org |url=http://pbdb.org/cgi-bin/bridge.pl?a=displayReference&reference_no=11969 | archive-url = https://web.archive.org/web/20160304033317/http://fossilworks.org/bridge.pl?reference_no=11969&action=referenceInfo | archive-date = 4 March 2016}}</ref> better known as Dr. Albert Koch's "Hydrarchos". {{Harvnb|Kellogg|1936}}, synonymized it with ''[[Pontogeneus]] priscus'', which a 2005 study declared a ''[[nomen dubium]]''.<ref>{{Cite journal | last = Uhen | first = M. D. | title = A new genus and species of archaeocete whale from Mississippi | year = 2005 | journal = Mississippi Geology | volume = 43 | issue = 3 | pages = 157–172}}</ref>

====Reassigned species====
[[File:Basilosaurus cetoides recon.png|thumb|Restoration of ''B. cetoides'']]
* ''Basilosaurus drazindai'' was named by a 1997 study based on a single lumbar vertebra. Originally, the species was thought to have lived in [[Pakistan]] and the [[UK]].<ref name="New Archaeoceti 2027"/> It was later declared a ''nomen dubium'' by Uhen (2013), but Gingerich and Zouhri (2015) reassigned it to the genus ''[[Eocetus]]''. This species was at one point in time concluded to be the earliest record of the genus ''Basilosaurus'', before its reclassification.<ref>{{cite book |chapter=Middle to Late Eocene Basilosaurines and Dorudontines |doi=10.1007/978-1-4899-0159-0_2 |title=The Emergence of Whales |pages=29–61 |year=1998 |last1=Uhen |first1=Mark D. |isbn=978-1-4899-0161-3 }}</ref><ref>{{Paleodb|53163|Basilosaurus drazindai}}. Retrieved August 2013.</ref><ref name=GZ2015>{{cite journal | last1 = Gingerich | first1 = Philip D. | last2 = Zouhri | first2 = Samir | year = 2015 | title = New fauna of archaeocete whales (Mammalia, Cetacea) from the Bartonian middle Eocene of southern Morocco | journal = Journal of African Earth Sciences | volume = 111| pages = 273–286| doi = 10.1016/j.jafrearsci.2015.08.006 | bibcode = 2015JAfES.111..273G }}</ref>
* ''Zeuglodon elliotsmithii'', ''Z. sensitivius'', and ''Z. zitteli'' were synonymized and grouped under the genus ''[[Saghacetus]]'' by a 1992 study.<ref>{{Cite journal| last = Gingerich | first = P. D. | author-link = Philip D. Gingerich| title = Marine Mammals (Cetacean and Sirenia) from the Eocene of Gebel Mokattam and Fayum, Egypt: Stratigraphy, Age, and Paleoenvironments| year = 1992 | journal = University of Michigan Papers on Paleontology | volume = 30 | pages = 1–84| oclc = 26941847| hdl = 2027.42/48630 }}</ref>
* ''Zeuglodon paulsoni'' from [[Ukraine]] (then the Russian Empire) was named by {{Harvnb|Brandt|1873}}. It was synonymized with ''[[Platyosphys]]'' but is now considered ''nomen dubium''. Gingerich and Zouhri (2015), however, maintain ''Platyosphys'' as valid.<ref name=GZ2015/><ref>{{Cite journal| last1 = Gol'din | first1 = Pavel| last2 = Zvonok | first2 = Evgenij| title = ''Basilotritus uheni'', a New Cetacean (Cetacea, Basilosauridae) from the Late Middle Eocene of Eastern Europe| year = 2013 | journal = Journal of Paleontology | volume = 87 | issue = 2 | pages = 254–268| doi = 10.1666/12-080R.1| bibcode = 2013JPal...87..254G| s2cid = 83864139}}</ref>
* ''Basilosaurus caucasicus'' also known as ''Basilosaurus caucasicum'' or ''Zeuglodon caucasicum'' was a species described in the [[Russian Empire]], it gets its name from the [[Caucasus]] of where it was found in the 1890s.<ref>{{cite journal |title=On Zeuglodont and other Cetacean Remains from the Tertiary of the Caucasus |journal=Proceedings of the Zoological Society of London |volume=1892 |issue=4 |pages=558–581 |doi=10.1111/j.1096-3642.1892.tb01782.x |year=2009 |last1=Lydekker |first1=R. |url=https://www.biodiversitylibrary.org/part/72835 |access-date=25 July 2021 |archive-date=24 November 2020 |archive-url=https://web.archive.org/web/20201124064635/https://www.biodiversitylibrary.org/part/72835 |url-status=live }}</ref> The fossil was reassigned to the toothed whale ''[[Microzeuglodon]] caucasicum''.<ref>{{cite web |title=†Microzeuglodon caucasicum Lydekker 1893 (toothed whale) |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=90636 |website=Fossilworks}}</ref>
* ''Basilosaurus harwoodi ''was discovered in the [[Murray River]] near [[Wellington, South Australia|Wellington]] in [[South Australia]]. This species classification was controversial; T. S. Hall (1911) placed ''Basilosaurus harwoodi'' (or ''Zeuglodon harwoodi'') in the genus ''[[Metasqualodon]]''.<ref>{{cite web |title=†Metasqualodon harwoodi Sanger 1881 (whale) |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=63492 |website=Fossilworks.org |access-date=15 August 2019}}</ref><ref>{{cite journal |title=On a molar tooth of Zeuglodon from the Tertiary beds on the Murray River near Wellington, S.A. |journal=Proceedings of the Linnean Society of New South Wales |url=https://books.google.com/books?id=clMFAAAAQAAJ&q=On+a+molar+tooth+of+Zeuglodon+from+the+Tertiary+beds+on+the+Murray+River+near+Wellington,+S.A.+Proceedings+of+the+Linnean+Society+of+New+South+Wales&pg=PA298|year = 1881|bibcode=1881PLSNS...5..298S |last1=Sanger |first1=E. B. |volume=5 |page=298 |doi=10.5962/bhl.part.15884 }}</ref>
*In 1906, German naturalist [[Othenio Abel]] thought fossils from the Eocene of Alabama, previously described in 1900 as being a ''Basilosaurus'' hip bone by American zoologist [[Frederic Augustus Lucas]], represented the shoulder of a large bird similar to ''[[Gastornis]]'', and named it ''Alabamornis gigantea''.<ref>{{cite journal|last=Abel|first=O.|author-link=Othenio Abel|year=1906|title=Ueber den als Beckengurtel von Zeuglodon beschriebenen Schultergurtel eines Vogels aus dem Eocan von Alabama|trans-title=On the shoulder girdle of a bird from the Eocene of Alabama described as a pelvic girdle of ''Zeuglodon''|journal=Centralblatt für Mineralogie, Geologie und Paläontologie |volume=15|pages=450–458}}</ref> Lucas later countered his conclusion in 1908 as he reassigned the fossil specimens to the original conclusion of a ''Basilosaurus'' hip bone.<ref>{{cite journal |first=F. A.|last=Lucas|author-link=Frederic Augustus Lucas|title=Discussion and Correspondence: is ''Alabamornis'' a bird? |journal=Science |date=1908 |volume=28 |issue=686|url=https://books.google.com/books?id=2JkSAAAAYAAJ&pg=RA1-PA311|page=311|doi=10.1126/science.27.686.311|pmid=17770689}}</ref>

== Description ==
[[File:Basilosaurus SIZE 01.png|thumb|left|Size compared to a human]]

''Basilosaurus'' is one of the largest animals known to exist between the [[Cretaceous–Paleogene extinction event|K–Pg extinction event]] 66 million years ago (mya) and around 15 million years ago when modern [[cetacea]]ns began to reach enormous sizes.<ref>{{cite web |url=https://naturalhistory.si.edu/onehundredyears/featured_objects/Basilosaurus.html |title=Explore Our Collections Basilosaurus |website=Smithsonian natural history museum |archive-url= https://web.archive.org/web/20160331223414/https://naturalhistory.si.edu/onehundredyears/featured_objects/Basilosaurus.html |archive-date=31 March 2016 }}</ref><ref>{{cite journal|year=2012|title=Evolution of Whales from Land to Sea|journal=Proceedings of the American Philosophical Society|volume=156|issue=3|pages=309–323|url=http://prod.lsa.umich.edu/content/dam/paleontology-assets/paleontology-documents/1560305Gingerich.pdf|last1=Gingerich|first1=P. D.|access-date=31 July 2019|archive-date=18 January 2021|archive-url=https://web.archive.org/web/20210118150642/http://prod.lsa.umich.edu/content/dam/paleontology-assets/paleontology-documents/1560305Gingerich.pdf|url-status=live}}</ref> ''B. cetoides'' measured {{convert|17|-|20|m|ft}} long and ''B. isis'' measured {{convert|15|-|18|m|ft}} long.<ref name=Basilo2019/> A 1998 study estimated that ''B. cetoides'' weighed more than {{convert|5.8|MT|ST}} and ''B. isis'' weighed nearly {{convert|6.5|MT|ST}},<ref>{{cite book|last1=Gingerich|first1=P.D.|editor1=Thewissen, J. G. M.|chapter=15. Paleobiological perspectives on Mesonychia, Archaeoceti, and the origin of whales|title=The Emergence of Whales: Evolutionary Patterns in the Origin of Cetacea|chapter-url=http://www-personal.umich.edu/~gingeric/PDFfiles/PDG341_OriginWhales.pdf|publisher=Springer|location=New York|year=1998|pages=423–449|doi=10.1007/978-1-4899-0159-0|isbn=978-1-4899-0159-0|s2cid=30660655|access-date=8 September 2013|archive-date=18 May 2022|archive-url=https://web.archive.org/web/20220518203140/http://www-personal.umich.edu/~gingeric/PDFfiles/PDG341_OriginWhales.pdf|url-status=live}}</ref> while the 2025 study estimated that a {{convert|18.35|m|ft}} long ''B. cetoides'' weighed {{convert|15|MT|ST}}.<ref>{{cite journal|author1=Paul, G.S.|author2=Larramendi, A.|year=2025|title=Further trimming down the marine heavyweights: ''Perucetus colossus'' did not come close to, much less exceed, the tonnage of blue whales, and the latter are not ultra-sized either|journal=Palaeontologia Electronica|volume=28|issue=1|at=28.1.a6|doi=10.26879/1435|url=https://palaeo-electronica.org/content/2025/5431-trimming-down-perucetus|doi-access=free}}</ref> ''Basilosaurus'' is distinguished from other genera of basilosaurids by its larger body size and its more elongated posterior thoracic, lumbar, and anterior caudal [[vertebrae]]. ''Basilosaurus'' does not have the vertically oriented metapophyses seen in its closest relative the basilosaurid known as ''[[Basiloterus]]''. ''Basilosaurus'' is considered to be the largest of archeocete whales.<ref name="New Archaeoceti 2027">{{Cite journal| last1 = Gingerich | first1 = P. D.| last2 = Arif | first2 = M| last3 = Bhatti | first3 = M Akram| last4 = Anwar | first4 = M| last5 = Sanders | first5 = William J| title = ''Basilosaurus drazindai'' and ''Basiloterus hussaini'', New Archaeoceti (Mammalia, Cetacea) from the Middle Eocene Drazinda Formation, with a Revised Interpretation of Ages of Whale-Bearing Strata in the Kirthar Group of the Sulaiman Range, Punjab (Pakistan)| year = 1997 | journal = Contributions from the Museum of Paleontology, University of Michigan | volume = 30 | issue = 2 | pages = 55–81| oclc = 742731913 | hdl = 2027.42/48652}}</ref><ref>{{cite web |title=Basilosaurus description |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=36681&is_real_user=1 |website=PBDB |access-date=23 July 2019 |archive-date=6 August 2021 |archive-url=https://web.archive.org/web/20210806225248/https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=36681&is_real_user=1 |url-status=live }}</ref>

=== Cranium ===
[[File:Basilosaurus isis and cetoides skulls compared.png|thumb|right|upright|Comparison of the skulls of ''Basilosaurus isis'' (fossil at [[Naturmuseum Senckenberg]], top) and ''B. cetoides'' (fossil from the [[North American Museum of Ancient Life]], bottom)]]
The [[dental formula]] for ''B. isis'' is {{DentalFormula|upper=3.1.4.2|lower=3.1.4.3}}. The upper and lower molars and second to fourth premolars are double-rooted and high-crowned.<ref name=fahlke2012>{{Cite journal| last = Fahlke | first = Julia M.| title = Bite marks revisited – evidence for middle-to-late Eocene ''Basilosaurus isis'' predation on ''Dorudon atrox'' (both Cetacea, Basilosauridae)| year = 2012 | journal = Palaeontologia Electronica | volume = 15 | issue = 3| url = http://palaeo-electronica.org/content/pdfs/341.pdf}}</ref>

The head of ''Basilosaurus'' did not have room for a [[Melon (cetacean)|melon]] like modern toothed whales, and the brain was smaller in comparison, as well. They are not believed to have had the [[Animal echolocation|echolocation]] capabilities nor the social dynamics of extant cetaceans. {{citation needed|date=November 2024}}

A 2011 study concluded that the skull of ''Basilosaurus'' is asymmetrical like in modern toothed whales, and not, as previously assumed, symmetrical like in baleen whales and [[Even-toed ungulate|artiodactyls]] (which are closely related to cetaceans). In modern toothed whales, this asymmetry is associated with high-frequency sound production and echolocation, neither of which is thought to have been present in ''Basilosaurus''. This probably evolved to detect sound underwater, with a fatty sound-receiving pad in the mandible.<ref>{{Cite journal| last1 = Fahlke | first1 = Julia M.| last2 = Gingerich | first2 = Philip D.| last3 = Welsh | first3 = Robert C.| last4 = Wood | first4 = Aaron R.| title = Cranial asymmetry in Eocene archaeocete whales and the evolution of directional hearing in water| year = 2011 | journal = PNAS | volume = 108 | issue = 35 | pages = 14545–14548| doi = 10.1073/pnas.1108927108 | pmid=21873217 | pmc=3167538| bibcode = 2011PNAS..10814545F| doi-access = free}}</ref>

In the skull, the inner and middle ear are enclosed by a dense [[tympanic bulla]].<ref name="GinUhe-1998">{{Cite journal| last1 = Gingerich | first1 = P. D.| last2 = Uhen | first2 = Mark D.| title = Likelihood estimation of the time of origin of Cetacea and the time of divergence of Cetacea and Artiodactyla| year = 1998 | journal = Palaeontologia Electronica | volume = 1 | issue = 2 | page = 4| url = http://palaeo-electronica.org/1998_2/ging_uhen/text.pdf }}</ref> The [[Synapomorphy|synapomorphic]] cetacean air [[Sinus (anatomy)|sinus]] system is partially present in basilosaurids, including the pterygoid, peribullary, maxillary, and frontal sinuses.<ref>{{Cite journal| last1 = Racicot | first1 = Rachel A.| last2 = Berta | first2 = Annalisa| title = Comparative Morphology of Porpoise (Cetacea: Phocoenidae) Pterygoid Sinuses: Phylogenetic and Functional Implications| year = 2013 | journal = Journal of Morphology | volume = 274 | issue = 1 | doi=10.1002/jmor.20075 | pmid = 22965565| page=50<!-- only citing page 50 -->| bibcode = 2013JMorp.274...49R| s2cid = 2617769}}</ref> The [[periotic bone]], which surrounds the inner ear, is partially isolated. The [[mandibular canal]] is large and laterally flanked by a thin bony wall, the pan bone or acoustic [[Fenestra (anatomy)|fenestra]]. These features enabled basilosaurs to hear directionally in water.<ref name="GinUhe-1998" />

The ear of basilosaurids is more derived than those in earlier [[archaeocete]]s, such as [[Remingtonocetidae|remingtonocetids]] and [[Protocetidae|protocetids]], in the acoustic isolation provided by the air-filled sinuses inserted between the ear and the skull. The basilosaurid ear did, however, have a large [[Ear canal|external auditory meatus]], strongly reduced in modern cetaceans, but, though this was probably functional, it can have been of little use under water.<ref>{{Cite journal |last1=Nummela |first1=Sirpa |last2=Thewissen |first2=J. G. M. |last3=Bajpai |first3=Sunil |last4=Hussain |first4=Taseer|last5=Kumar |first5=Kishor |s2cid=4372872 |title=Eocene evolution of whale hearing |year=2004 |journal=Nature |volume=430 |issue=7001 |pages=776–778 |doi=10.1038/nature02720 |pmid=15306808 |bibcode=2004Natur.430..776N }}</ref>

=== Hind limbs ===
[[File:Basilosaurus isis hindlimb.JPG|thumb|right|upright|''B. isis'' hind limb]]
A {{Convert|16|m|ft|adj=mid|sp=us}} individual of ''B. isis'' had {{Convert|35|cm|in|adj=mid|-long|sp=us}} hind limbs with fused tarsals and only three digits. The limited size of the limb and the absence of an articulation with the sacral vertebrae make a locomotory function unlikely.<ref>{{Cite journal | last1 = Bejder | first1 = Lars | last2 = Hall | first2 = Brian K. | author2-link = Brian K. Hall | title = Limbs in whales and limblessness in other vertebrates: mechanisms of evolutionary and developmental transformation and loss | year = 2002 | journal = Evolution and Development | volume = 4 | issue = 6 | pages = 445–458 | url = http://whitelab.biology.dal.ca/lb/Bejder%20and%20Hall.pdf | doi = 10.1046/j.1525-142x.2002.02033.x | pmid = 12492145 | s2cid = 8448387 | access-date = 1 October 2005 | archive-date = 10 April 2021 | archive-url = https://web.archive.org/web/20210410222928/http://whitelab.biology.dal.ca/lb/Bejder%20and%20Hall.pdf | url-status = live }}</ref> Analysis has shown that the reduced limbs could rapidly adduct between only two positions.<ref name="pmid-17836967">{{cite journal |title=Hind limbs of eocene basilosaurus: evidence of feet in whales. |journal=Science |volume=249 |issue=4965 |pages=154–157 |pmid=17836967 |bibcode=1990Sci...249..154G |last1=Gingerich |first1=Philip D. |last2=Smith |first2=B. Holly|author2-link=B. Holly Smith |last3=Simons |first3=Elwyn L. |s2cid=35307146 |year=1990 |doi=10.1126/science.249.4965.154 }}</ref> Possible uses for the structure have been given, such as [[clasper]]-like body functions (compare to the function of [[pelvic spur]]s, the last vestiges of limbs in certain modern snakes). These limbs would have been used to guide the animals' long bodies during mating.<ref>{{cite web |title=Basilosaurid FOSSIL MAMMAL |url=https://www.britannica.com/animal/basilosaurid |website=Encyclopedia Britannica}}</ref>

=== Spine and movement ===
A complete ''Basilosaurus'' skeleton was found in 2015, and several attempts have been made to reconstruct the vertebral column from partial skeletons. {{Harvnb|Kellogg|1936}} estimated a total of 58 vertebrae, based on two partial and nonoverlapping skeletons of ''B. cetoides'' from Alabama. More complete fossils uncovered in Egypt in the 1990s allowed a more accurate estimation: the vertebral column of ''B. isis'' has been reconstructed from three overlapping skeletons to a total of 70 vertebrae with a vertebral formula interpreted as seven cervical, 18 thoracic, 20 lumbar and sacral, and 25 caudal vertebrae. The vertebral formula of ''B. cetoides'' can be assumed to be the same.<ref name=zalmout2000/>
[[File:Basilosaurus cetoides.png|thumb|left|[[Paleoart|Restoration]] of ''Basilosaurus cetoides'']]
''Basilosaurus'' has an anguilliform ([[eel]]-like) body shape because of the elongation of the [[Body of vertebra|centra]] of the thoracic through anterior caudal vertebrae. In life, these vertebrae were filled with marrow, and because of the enlarged size, this made them buoyant. ''Basilosaurus'' probably swam predominantly in two dimensions at the sea surface, in contrast to the smaller ''[[Dorudon]]'', which was likely a diving, three-dimensional swimmer.<ref>{{Cite book| last = Gingerich| first = P. D.| chapter = Paleobiological Perspectives on Mesonychia, Archaeoceti, and the Origin of Whales| pages = 424–439| title = The Emergence of Whales: Evolutionary Patterns in the Origin of Cetacea| series = Advances in Vertebrate Paleobiology| volume = 1| editor-last = Thewissen| editor-first = J. G. M.| year = 1998| publisher = Springer| chapter-url = http://www-personal.umich.edu/~gingeric/PDFfiles/PDG341_OriginWhales.pdf| isbn = 978-0-306-45853-8| access-date = 8 September 2013| archive-date = 18 May 2022| archive-url = https://web.archive.org/web/20220518203140/http://www-personal.umich.edu/~gingeric/PDFfiles/PDG341_OriginWhales.pdf| url-status = live}}</ref> The skeletal anatomy of the tail suggests that a small fluke was probably present, which would have aided only vertical motion.<ref>{{cite web |title=Basilosaurus spp. |url=https://www.nyit.edu/medicine/basilosaurus_spp |website=College of Osteopathic Medicine |publisher=Robert Boessenecker and Jonathan Geisler |access-date=22 June 2019 |archive-date=31 December 2018 |archive-url=https://web.archive.org/web/20181231105613/https://www.nyit.edu/medicine/basilosaurus_spp |url-status=live }}</ref>

Similarly sized thoracic, lumbar, sacral, and caudal vertebrae imply that it moved in an [[Fish locomotion#Swimming|anguilliform]] fashion, but predominantly in the vertical plane. Paleontologist [[Philip D. Gingerich]] theorized that ''Basilosaurus'' may also have moved in a very odd, horizontal anguilliform fashion to some degree, something completely unknown in modern cetaceans. The vertebrae appear to have been hollow, and likely also fluid-filled. This would imply that ''Basilosaurus'' typically functioned in only two dimensions at the ocean surface, compared with the three-dimensional habits of most other cetaceans. Judging from the relatively weak axial musculature and the thick bones in the limbs, ''Basilosaurus'' is not believed to have been capable of sustained swimming or deep diving, or [[terrestrial locomotion]].<ref>{{cite book |title=Great Transformations in Vertebrate Evolution |date=July 2015 |publisher=KENNETH P. DIAL, NEIL SHUBIN, AND ELIZABETH L. BRAINERD |isbn=978-0-226-26825-5 |url=https://books.google.com/books?id=zb5TCgAAQBAJ&q=basilosaurus+moved+like+an+eel&pg=PA248}}</ref>

== Paleobiology ==
=== Feeding ===
[[File:Basilosaurus isis muscles.jpg|thumb|upright|''B. isis'' jaw muscles]]
The cheek teeth of ''Basilosaurus'' retain a complex morphology and functional [[Occlusion (dentistry)|occlusion]]. Heavy wear on the teeth reveals that food was first chewed then swallowed.<ref name="GinUhe-1998" /> Scientists were able to estimate the [[bite force]] of ''Basilosaurus isis'' by analyzing the scarred skull bones of another species of prehistoric whale, ''Dorudon'', and concluded that it could exert a maximum bite force of at least {{convert|16400|N|lbf}} and could possibly exceed {{convert|20000|N|lbf}},<ref>{{cite journal|last1=Snively|first1=E.|last2=Fahlke|first2=J. M.|last3=Welsh|first3=R. C.|year=2015|title=Bone-Breaking Bite Force of ''Basilosaurus isis'' (Mammalia, Cetacea) from the Late Eocene of Egypt Estimated by Finite Element Analysis|journal=PLOS ONE|volume=10|issue=2|article-number=e0118380|doi=10.1371/journal.pone.0118380|pmid=25714832|pmc=4340796|bibcode=2015PLoSO..1018380S|doi-access=free}}</ref> roughly equivalent to the range between modern [[American Alligator|alligators]]<ref name="lappin">{{cite journal |title=Comparison of bite-force performance between long-term captive and wild American alligators (Alligator mississippiensis) |journal=[[Journal of Zoology]] |volume=262 |issue=1 |pages=21–28 |url=http://www.alligatorfarm.us/images/Research/Erickson%20et%20al.%202004.pdf |doi=10.1017/S0952836903004400 |year=2004 |last1=Erickson |first1=Gregory M. |last2=Lappin |first2=A. Kristopher |last3=Parker |first3=Trevor |last4=Vliet |first4=Kent A. |access-date=6 August 2024 |archive-date=8 July 2024 |archive-url=https://web.archive.org/web/20240708075634/http://www.alligatorfarm.us/images/Research/Erickson%20et%20al.%202004.pdf |url-status=live }}</ref> and [[crocodiles]].<ref name="erickson">{{cite journal|last=Erickson|first=GM|author2=Gignac PM |author3=Steppan SJ |author4=Lappin AK |author5=Vliet KA |year=2012|title=Insights into the Ecology and Evolutionary Success of Crocodilians Revealed through Bite-Force and Tooth-Pressure Experimentation|journal=PLOS ONE|volume=7|issue=3|article-number=e31781|doi=10.1371/journal.pone.0031781|pmid=22431965|pmc=3303775|display-authors=etal|bibcode=2012PLoSO...731781E|doi-access=free}}</ref>
[[File:Fig 7. Cranial remains of juvenile Dorudon atrox.png|left|thumb|Remains of at least two juvenile ''Dorudon atrox'' found within the stomach of a ''Basilosaurus isis'']]
Analyses of the stomach contents of ''B. cetoides'' has shown that this species fed exclusively on fish and large sharks, while bite marks on the skulls of juvenile ''Dorudon'' have been matched with the dentition of ''B. isis'', suggesting a dietary difference between the two species, similar to that found in different populations of modern [[killer whale]]s.<ref name=fahlke2012/> It was probably an active predator rather than a scavenger.<ref>{{cite journal|last1=Snively|first1=Eric|last2=Fahlke|first2=Julia M.|last3=Welsh|first3=Robert C.|title=Bone-Breaking Bite Force of ''Basilosaurus isis'' (Mammalia, Cetacea) from the Late Eocene of Egypt Estimated by Finite Element Analysis|journal=PLOS ONE|date=25 February 2015|volume=10|issue=2|article-number=e0118380|doi=10.1371/journal.pone.0118380|pmid=25714832|pmc=4340796|bibcode=2015PLoSO..1018380S|doi-access=free}}</ref> The discovery of juvenile ''Dorudon'' at Wadi Al Hitan bearing distinctive bite marks on their skulls indicates that ''B. isis'' would have aimed for the skulls of its victims to kill its prey, and then subsequently torn its meals apart, based on the disarticulated remains of the ''Dorudon'' skeletons. The finding further cements theories that ''B. isis'' was an [[apex predator]] that may have hunted newborn and juvenile ''Dorudon'' at Wadi Al Hitan when mothers of the latter came to give birth.<ref name=Basilo2019/> The stomach contents of an elderly male '' B. isis''  not only includes ''Dorudon'' but the fish ''[[Pycnodus]] mokattamensis''.<ref name=Basilo2019>{{cite journal |last1=Voss |first1=Manja |last2=Antar |first2=Mohammed Sameh M. |last3=Zalmout |first3=Iyad S. |last4=Gingerich |first4=Philip D. |title=Stomach contents of the archaeocete ''Basilosaurus isis'': Apex predator in oceans of the late Eocene |journal=PLOS ONE |volume=14 |issue=1 |at=e0209021 |year=2019 |doi=10.1371/journal.pone.0209021 |pmid=30625131 |pmc=6326415 |bibcode=2019PLoSO..1409021V |doi-access=free }}</ref>

===Paleoecology===
[[File:Basilosaurus and Dorudon skeletons - Voss et al 2019.tif|thumb|left|''Basilosaurus isis'' (A) and ''Dorudon atrox'' (B) size comparison]]
''Basilosaurus'' would have been the top predator of its environment.<ref>{{cite web |title=15-meter-long ancient whale ''Basilosaurus isis'' was top marine predator |url=https://www.sciencedaily.com/releases/2019/01/190109142626.htm |website=Science Daily |access-date=11 July 2019 |archive-date=11 July 2019 |archive-url=https://web.archive.org/web/20190711224451/https://www.sciencedaily.com/releases/2019/01/190109142626.htm |url-status=live }}</ref> It lived in the warm tropical environment of the Eocene in areas abundant with sea grasses, such as ''[[Thalassodendron]]'', ''[[Thalassia (plant)|Thalassia]]'' (also known as turtle grass) and ''[[Halodule]]''.<ref>{{cite web |title=Florida Lime Works quarry (Eocene of the United States) |url=https://paleobiodb.org/classic/basicCollectionSearch?collection_no=49882&is_real_user=1 |website=PBDB}}</ref><ref>{{cite web |title=Wadi Hitan ZV-74 (Eocene of Egypt) |url=https://paleobiodb.org/classic/basicCollectionSearch?collection_no=175726&is_real_user=1 |website=PBDB}}</ref><ref>{{cite web |title=Eocene Epoch |url=https://www.britannica.com/science/Eocene-Epoch |website=Encyclopedia Britannica |date=9 December 2023 |access-date=11 July 2019 |archive-date=29 June 2015 |archive-url=https://web.archive.org/web/20150629134755/https://www.britannica.com/science/Eocene-Epoch |url-status=live }}</ref> Based on the localities where its fossils are discovered, ''Basilosaurus'' would have preferred to live in the shallows, specifically in the middle to outer [[neritic zone]]s of the [[inland sea]].<ref>{{Cite journal |last1=Smith |first1=Kathlyn M. |last2=Hastings |first2=Alexander K. |last3=Bebej |first3=Ryan M. |last4=Uhen |first4=Mark D. |date=2022 |title=Biogeographic, stratigraphic, and environmental distribution of Basilosaurus (Mammalia, Cetacea) in North America with a review of the late Eocene shoreline in the southeastern coastal plain |url=https://www.cambridge.org/core/journals/journal-of-paleontology/article/abs/biogeographic-stratigraphic-and-environmental-distribution-of-basilosaurus-mammalia-cetacea-in-north-america-with-a-review-of-the-late-eocene-shoreline-in-the-southeastern-coastal-plain/5DAA31E6C6D4EB745D22FC6F837AC0A8 |journal=Journal of Paleontology |volume=96|issue=2|language=en |pages=439–451 |doi=10.1017/jpa.2021.90 |bibcode=2022JPal...96..439S |s2cid=240244165 |issn=0022-3360|url-access=subscription }}</ref> It would have coexisted with the dolphin-like ''Dorudon'',<ref>{{cite web |title=†Dorudon Gibbes 1845 (whale) |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=36709&is_real_user=1 |website=PBDB |access-date=11 July 2019 |archive-date=5 September 2021 |archive-url=https://web.archive.org/web/20210905185427/https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=36709&is_real_user=1 |url-status=live }}</ref> the whales ''[[Cynthiacetus]]'' and ''[[Basiloterus]]'',<ref>{{cite web |title=†Cynthiacetus Uhen 2005 (whale) |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=63143&is_real_user=1 |website=PBDB |access-date=12 July 2019 |archive-date=24 July 2020 |archive-url=https://web.archive.org/web/20200724103529/https://www.paleobiodb.org/classic/checkTaxonInfo?taxon_no=63143&is_real_user=1 |url-status=live }}</ref> the primitive [[sirenia]]n ''[[Protosiren]]'', the early elephant ''[[Moeritherium]]'',<ref>{{cite book |title=The topography and geology of the Fayum province of Egypt |date=1905 |pages=87–88 |url=https://archive.org/details/cu31924004049338/page/n6 |location=Cairo |publisher=National Printing Dept. }}</ref><ref>{{cite journal |title=A Reappraisal of Some Paleogene Turtles from the Southeastern United States |journal=Journal of Vertebrate Paleontology |volume=25 |issue=4 |pages=979–982 |doi=10.1671/0272-4634(2005)025[0979:AROSPT]2.0.CO;2 |jstor=4524524 |year=2005 |last1=Holroyd |first1=Patricia A. |last2=Parham |first2=James F. |last3=Hutchison |first3=J. Howard |s2cid=130961045 }}{{Relevance inline|date=September 2019}}</ref><ref>{{cite periodical |title=North American Eocene Sea Cows (Mammalia: Sirenia) |periodical=Smithsonian Contributions to Paleobiology |number=52 |year=1982 |hdl=10088/1974 |doi=10.5479/si.00810266.52.1 |last1=Domning|first1=Daryl P.|last2=Morgan|first2=Gary S.|last3=Ray|first3=Clayton E.|pages=1–69 }}</ref>  the sea turtle ''[[Puppigerus]]''<ref>{{cite web |title=†Puppigerus Cope 1870 (sea turtle) |url=https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=36371 |website=PBDB |access-date=11 July 2019 |archive-date=6 October 2021 |archive-url=https://web.archive.org/web/20211006194602/https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=36371 |url-status=live }}</ref> and many sharks, such as ''[[Galeocerdo alabamensis]]'',<ref>{{cite web |title=†Galeocerdo alabamensis Leriche 1942 (tiger shark) |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=125024 |website=Fossilworks}}</ref> ''[[Physogaleus]]'', ''[[Otodus]]'', ''[[Squatina prima]]'', ''[[Striatolamia]]'', ''[[Otodus sokolovi|Carcharocles sokolovi]]'' and ''[[Isurus praecursor]]''.<ref>{{cite web |title=Hardie Kaolin Mine (Eocene of the United States) |url=https://paleobiodb.org/classic/basicCollectionSearch?collection_no=45640&is_real_user=1 |website=PBDB}}</ref>

==Extinction==
{{see also|Eocene–Oligocene extinction event|}}
''Basilosaurus'' fossil record seems to end at about 35–33.9 mya.<ref>{{cite web |title=†Basilosaurus Harlan 1834 (whale)|url=https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=36681 |website=PBDB}}</ref> ''Basilosaurus'' extinction coincides with the Eocene–Oligocene extinction event which happened 33.9 mya,<ref>{{Cite journal |last1=Ivany |first1=Linda C. |last2=Patterson |first2=William P. |last3=Lohmann |first3=Kyger C. |s2cid=4408282 |title=Cooler winters as a possible cause of mass extinctions at the Eocene/Oligocene boundary |journal=Nature |volume=407 |issue=6806 |pages=887–890 |doi=10.1038/35038044 |pmid=11057663 |year=2000 |hdl=2027.42/62707 |bibcode=2000Natur.407..887I |url=https://deepblue.lib.umich.edu/bitstream/2027.42/62707/1/407887a0.pdf |access-date=23 September 2019 |archive-date=19 May 2020 |archive-url=https://web.archive.org/web/20200519203924/https://deepblue.lib.umich.edu/bitstream/handle/2027.42/62707/407887a0.pdf?sequence=1 |url-status=live }}</ref> which also resulted in the extinction of almost all other archaeocetes.{{sfn|Kellogg|1936|p=1–336}} The event has been attributed to volcanic activity, meteor impacts, or a sudden change in climate (such as the environment getting cooler), the latter of which might have caused changes in the ocean by disrupting oceanic circulation, thus limiting the numbers of prey for predators like ''Basilosaurus'' to feed on.<ref name="Ging-Alabama"/><ref>{{cite web |title=Russia's Popigai Meteor Crash Linked to Mass Extinction |url=https://news.yahoo.com/russias-popigai-meteor-crash-linked-mass-extinction-113359696.html |website=Yahoo news |date=16 June 2014 |publisher=Becky Oskin, Senior Writer |access-date=10 May 2019 |archive-date=3 March 2016 |archive-url=https://web.archive.org/web/20160303223733/http://news.yahoo.com/russias-popigai-meteor-crash-linked-mass-extinction-113359696.html |url-status=live }}</ref><ref>{{Cite journal |last1=Molina |first1=Eustoquio |last2=Gonzalvo |first2=Concepción |last3=Ortiz |first3=Silvia |last4=Cruz |first4=Luis E. |date=28 February 2006 |title=Foraminiferal turnover across the Eocene–Oligocene transition at Fuente Caldera, southern Spain: No cause–effect relationship between meteorite impacts and extinctions |journal=Marine Micropaleontology |volume=58 |issue=4 |pages=270–286 |doi=10.1016/j.marmicro.2005.11.006 |bibcode=2006MarMP..58..270M}}</ref> ''Basilosaurus'' went extinct leaving no descendants, along with the rest of the Archaeocetes. After their extinction, the new currents and deep ocean upwelling created a new environment that favored the evolutionary diversification of modern cetaceans (Neocetes) such as early toothed and baleen whales, from more advanced Archaeocetes that evolved the traits associated with Neocetes.<ref>{{Cite journal | last = Uhen | first = Mark D. | title = The Origin(s) of Whales | year = 2010 | journal = Annual Review of Earth and Planetary Sciences | volume = 38 | issue = 1 | pages = 189–219 | doi = 10.1146/annurev-earth-040809-152453 | bibcode = 2010AREPS..38..189U }}</ref>

==Classification==
Below is the phylogenetic analysis on the placement of ''Basilosaurus''. Two subfamilies exist in [[Basilosauridae]]: [[Basilosaurinae]] which includes ''Basilosaurus'', and [[Dorudontinae]]. These groups have been declared invalid in the past.<ref>{{cite web |title=†subfamily Dorudontinae Miller 1923 (whale) |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=53109 |website=Fossilwork}}</ref><ref>{{cite web |title=†subfamily Basilosaurinae Miller 1923 (whale) |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=53109 |website=Fossilworks}}</ref> ''Dorudon'' remains were once thought to represent juvenile ''Basilosaurus''.<ref>{{Harvnb|Gibbes|1847|pp=8–11}}; {{Harvnb|Agassiz|1848|pp=4–5}}</ref>
{{clade| style=font-size: 85%; line-height: 85%
|label1=†[[Basilosaurinae]]
|1={{clade
   |1={{clade
      |label1=
      |1={{clade
         |1=†'''''Basilosaurus'''''<span style="{{MirrorH}}">[[File:Basilosaurus cetoides recon.png|100 px]]</span>
         |2=†''[[Basiloterus]]''<span style="{{MirrorH}}">[[File:Basiloterus husseini.png|100 px]]</span>
         |3=†''[[Eocetus]]''}}
      |2=†''[[Platyosphys]]''<span style="{{MirrorH}}">[[File:Pachycetus paulsoni.png|100 px]]</span>}}
   |2=†''[[Pachycetus]]''<span style="{{MirrorH}}">[[File:Basilotritus uheni.png|100 px]]</span>}}
}}

==In popular culture==
The species ''B. cetoides'' is the [[List of U.S. state fossils|state fossil]] of [[Alabama]]<ref name="Ging-Alabama">{{cite web |last= Gingerich |first= Philip D. |title= ''Basilosaurus cetoides'' |website= Encyclopedia of Alabama |url= http://www.encyclopediaofalabama.org/face/Article.jsp?id=h-1386 |access-date= 24 August 2013 |archive-date= 13 March 2014 |archive-url= https://web.archive.org/web/20140313151405/http://www.encyclopediaofalabama.org/face/Article.jsp?id=h-1386 }}</ref> and [[Mississippi]].<ref>{{cite web | title = State Symbols | publisher = State of Mississippi | url = https://www.ms.gov/Visitors/About_Mississippi/State_Symbols | access-date = 24 August 2013 | url-status = live | archive-url = https://web.archive.org/web/20130822173541/http://www.ms.gov/content/Pages/Symbols.aspx | archive-date = 22 August 2013 }}</ref><ref>{{Citation |title=Fossil whale: State Fossil of Mississippi |number=Pamphlet 3 |publisher=Mississippi Department of Environmental Quality |date=1991 |url=https://www.mdeq.ms.gov/wp-content/uploads/2013/04/Pamphlet-3.pdf |access-date=9 May 2019 |archive-date=9 May 2019 |archive-url=https://web.archive.org/web/20190509145559/https://www.mdeq.ms.gov/wp-content/uploads/2013/04/Pamphlet-3.pdf |url-status=live }}</ref> During the early 19th century, ''B. cetoides'' fossils were so common (and sufficiently large) that they were regularly used as furniture in the American South.<ref>{{Cite book| last = Zimmer | first = Carl | author-link = Carl Zimmer| title = At the Water's Edge: Macroevolution and the Transformation of Life| year = 1998 | publisher = Free Press| isbn = 978-0-684-83490-0|page=141}}</ref>

''Basilosaurus'' is featured in the [[BBC]]'s ''[[Walking with...]]'' series in ''[[Walking with Beasts]]'' and ''[[Sea Monsters (TV series)|Sea Monsters]]''.<ref>{{cite web |title=Sea monster facts |url=https://www.bbc.co.uk/sn/prehistoric_life/dinosaurs/seamonsters/ |website=BBC |access-date=21 May 2019 |archive-date=24 February 2021 |archive-url=https://web.archive.org/web/20210224123847/http://www.bbc.co.uk/sn/prehistoric_life/dinosaurs/seamonsters/ |url-status=live }}</ref><ref>{{cite web |title=Walking with Beasts |url=https://www.bbc.co.uk/programmes/p0095rnz |website=BBC |access-date=9 December 2018}}</ref><ref>{{cite web |title=Sea Monsters: A Walking With Dinosaurs Trilogy |url=https://www.bbc.co.uk/programmes/p008c6n4/clips |website=BBC}}</ref>

In the 1851 novel ''[[Moby-Dick]]'' by [[Herman Melville]], [[Ishmael (Moby-Dick)|Ishmael]] cites the ''Basilosaurus'' during his studies as a possible whale fossil.<ref>{{cite book
 |last1                = Melville
 |first1               = Herman
 |year                 = 1951
 |chapter              = 104: The Fossil Whale
 |chapter-url          = https://en.wikisource.org/wiki/Moby-Dick_(1851)_US_edition/Chapter_104
 |title                = Moby Dick
 |language             = English
 |publication-place    = United States
 |publisher            = Harper and Brothers
 |isbn                 = 978-1-5023-6584-2
 |access-date          = 20 September 2022
|quote                = But by far the most wonderful of all cetacean relics was the almost complete vast skeleton of an extinct monster, found in the year 1842, on the plantation of Judge Creagh, in Alabama. The awe-stricken credulous slaves in the vicinity took it for the bones of one of the fallen angels. The Alabama doctors declared it a huge reptile, and bestowed upon it the name of ''Basilosaurus''. But some specimen bones of it being taken across the sea to Owen, the English Anatomist, it turned out that this alleged reptile was a whale, though of a departed species. A significant illustration of the fact, again and again repeated in this book, that the skeleton of the whale furnishes but little clue to the shape of his fully invested body. So Owen rechristened the monster ''Zeuglodon''; and in his paper read before the London Geological Society, pronounced it, in substance, one of the most extraordinary creatures which the mutations of the globe have blotted out of existence.
}}</ref>

==See also==
{{Portal|Cetaceans|Mammals|Marine life|Oceans|Paleontology}}
* [[Evolution of cetaceans]]
*[[List of cetaceans]]
**''[[Livyatan melvillei]]'' – occupied a similar ecological niche

== References ==
{{reflist|30em}}

=== Cited literature ===
{{Refbegin|40em}}
* {{Cite journal | last = Andrews | first = C. W. | author-link = Charles William Andrews | title = Further notes on the mammals of the Eocene of Egypt. Part III. | year = 1904 | journal = Geological Magazine | series = 5 | volume = 1 | issue = 5 | pages = 211–215 | url = https://archive.org/stream/geologicalmagazi511904wood#page/210/mode/2up | doi = 10.1017/s0016756800119624 | s2cid = 222700904 }}<!-- {{Harvnb|Andrews|1904}} -->
**{{cite web |title=Further notes on the mammals of the Eocene of Egypt. Part III |website=paleodb.org |url=https://paleodb.org/?a=displayReference&reference_no=11952 |url-status=live |archive-url=https://web.archive.org/web/20151115103745/http://fossilworks.org/cgi-bin/bridge.pl?reference_no=11952&action=displayReference |archive-date=15 November 2015 }}
* {{Cite book
 | last = Andrews | first = C. W.
 | title = A descriptive catalogue of the Tertiary Vertebrata of the Fayûm, Egypt
 | year = 1906 | publisher= British Museum (Natural History) | url = https://archive.org/stream/cu31924003891664#page/n299/mode/2up
 | oclc = 3675777}}<!-- {{Harvnb|Andrews|1906}} -->
* {{Cite journal |last=Agassiz |first=L. |author-link=Louis Agassiz |title=Letter from Prof. Agassiz, addressed to Dr. Gibbes, dated Charleston, December 23, 1847 |year=1848 |journal=Proceedings of the Academy of Natural Sciences of Philadelphia |volume=5 |url=https://www.biodiversitylibrary.org/item/84785#page/20/mode/2up |access-date=2 July 2013 |archive-date=25 February 2014 |archive-url=https://web.archive.org/web/20140225105620/http://www.biodiversitylibrary.org/item/84785#page/20/mode/2up |url-status=live }}
* {{Cite journal
 | last = Brandt | first = J. F., von | author-link = Johann Friedrich von Brandt
 | title = Über bisher in Russland gefundene Reste von Zeuglodonten
 | year = 1873 | journal = Mélanges Biologiques Tirés du Bulletin de l'Académie Impériale des Sciences de St. Pétersbourg | volume = 9 | pages = 111–112
 | url = https://www.biodiversitylibrary.org/item/109867#page/129/mode/1up
 }}<!-- {{Harvnb|Brandt|1873}} -->
**{{cite web |title=Uber bisher in Russland gefundene Reste von Zeuglodonten |website=paleodb.org |url=https://paleodb.org/?a=displayReference&reference_no=29257 |url-status=live |archive-url=https://web.archive.org/web/20160316075936/http://fossilworks.org/cgi-bin/bridge.pl?reference_no=29257&action=displayReference |archive-date=16 March 2016 }}
* {{Cite journal |last=Gibbes |first=Robert Wilson |title=On the fossil genus Basilosaurus, Harlan, ''(Zeuglodon'', Owen,) with a notice of specimens from the Eocene Green Sand of South Carolina |year=1847 |journal=Journal of the Academy of Natural Sciences of Philadelphia |url=https://www.biodiversitylibrary.org/item/84785#page/20/mode/2up |volume=1 |access-date=25 May 2022 |archive-date=25 February 2014 |archive-url=https://web.archive.org/web/20140225105620/http://www.biodiversitylibrary.org/item/84785#page/20/mode/2up |url-status=live }}
* {{Cite journal
 | last = Harlan | first = R. | author-link = Richard Harlan
 | title = Notice of fossil bones found in the Tertiary formation of the State of Louisiana
 | year = 1834 | journal = Transactions of the American Philosophical Society | volume = 4 | pages = 397–403
 | url = http://www.oceansofkansas.com/Harlan1834b.html 
 | oclc = 63356837 | jstor = 1004838| doi=10.2307/1004838| url-access = subscription}}<!-- {{Harvnb|Harlan|1834}} -->
* {{Cite book
 | last = Kellogg | first = R.
 | title = A review of the Archaeoceti | id = Publication no. 482
 | year = 1936 | location = Washington | publisher = Carnegie Institution of Washington
 | url = http://publicationsonline.carnegiescience.edu/publications_online/archaeoceti.pdf | format = PDF, 46.3 Mb
 | oclc =681376}}<!-- {{Harvnb|Kellogg|1936}} -->
* {{Cite journal
 | last = Owen | first = R. | s2cid = 84456321 | author-link = Richard Owen
 | title = Observations on the ''Basilosaurus'' of Dr. Harlan (''Zeuglodon cetoides'', Owen)
 | year =1839 | journal = Transactions of the Geological Society of London | volume = 6 | pages = 69–79
 | url = https://archive.org/stream/transactionsof261841geol#page/68/mode/2up
 | doi=10.1144/transgslb.6.1.69}}<!-- {{Harvnb|Owen|1839}} -->
**{{cite web |title=Observations on the Basilosaurus of Dr. Harlan (Zeuglodon cetoides) |website=paleodb.org |url=https://paleodb.org/cgi-bin/bridge.pl?a=displayReference&reference_no=15404 |archive-date=16 March 2016 |url-status=live |archive-url=https://web.archive.org/web/20160316081942/http://fossilworks.org/bridge.pl?reference_no=15404&action=referenceInfo }}
* {{cite book |last1=Koch |first1=Albert Carl |title=Description of the Hydrarchos harlani: a gigantic fossil reptile: lately discovered by the author in the state of Alabama |date=1845 |publisher=B. Owen, printer |url=https://archive.org/details/descriptionofhyd00koch |language=en }}
{{Refend}}

==Further reading==
{{Refbegin|40em}}
*{{Cite journal | last = Gidley | first = J. W. | author-link = James W. Gidley | title = A recently mounted ''Zeuglodon'' skeleton in the United States National Museum | year = 1913 | journal = Proceedings of the United States National Museum | volume = 44 | issue = 1975 | pages = 649–654 | url = https://archive.org/stream/proceedingsofuni441913unit#page/n831/mode/2up/search/A+recently+mounted+Zeuglodon | doi = 10.5479/si.00963801.44-1975.649 | ref = none }}
* {{Cite journal | last = Kellogg | first = R. | s2cid = 20126705 | author-link = Remington Kellogg | title = Description of two squalodonts recently discovered in the Calvert Cliffs, Maryland; and notes on the shark-toothed cetaceans | year = 1923 | journal = Proceedings of the United States National Museum | volume = 62 | issue = 2462 | pages = 1–69 | oclc = 82628874 | doi = 10.5479/si.00963801.62-2462.1 | hdl = 10088/15278 | url = https://www.biodiversitylibrary.org/part/53955 | ref = none }}
* {{Cite journal | last = Lucas | first = Frederic A. | s2cid = 161510206 | author-link = Frederic Augustus Lucas | title = The pelvic girdle of ''Zeuglodon'', ''Basilosaurus cetoides'' (Owen) with notes on other portions of the skeleton | year = 1900 | journal = Proceedings of the United States National Museum | volume = 23 | issue = 1211 | pages = 327–331 | oclc = 75278090 | doi = 10.5479/si.00963801.23-1211.327 | hdl = 2027/hvd.32044107351454 | url = https://www.biodiversitylibrary.org/part/26633 | ref = none }}
* {{Cite journal | last = Lydekker | first = R. | author-link = Richard Lydekker | title = 4. On Zeuglodont and other Cetacean Remains from the Tertiary of the Caucasus | year = 1892 | journal = Proceedings of the Zoological Society of London | volume = 60 | issue = 4 | pages = 558–581 | url = https://www.biodiversitylibrary.org/page/31849097#page/652/mode/1up | doi = 10.1111/j.1096-3642.1892.tb01782.x | oclc = 819196877 | ref = none | access-date = 13 January 2018 | archive-date = 7 June 2023 | archive-url = https://web.archive.org/web/20230607154912/https://www.biodiversitylibrary.org/page/31849097#page/652/mode/1up | url-status = live }}
**{{cite web |title=On Zeuglodont and other cetacean remains from the Tertiary of the Caucasus |website=paleodb.org |url=https://paleodb.org/cgi-bin/bridge.pl?a=displayReference&reference_no=12047 |archive-url=https://web.archive.org/web/20160316074852/http://fossilworks.org/bridge.pl?reference_no=12047&action=referenceInfo |archive-date=16 March 2016 |url-status=live }}
* {{Cite journal | last = Sanger | first = E. B. | title = On a molar tooth of ''Zeuglodon'' from the Tertiary beds on the Murray River near Wellington, S.A. | year = 1881 | journal = Proceedings of the Linnean Society of New South Wales | volume = 1 | issue = 5 | pages = 298–300 | url = http://www.biodiversityheritagelibrary.org/page/6455963#page/322/mode/1up | archive-url = https://web.archive.org/web/20160306031425/http://biodiversityheritagelibrary.org/page/6455963#page/322/mode/1up | archive-date = 6 March 2016 | doi = 10.5962/bhl.part.15884 | bibcode = 1881PLSNS...5..298S | ref = none }}
**{{cite web |title=On a molar tooth of Zeuglodon from the Tertiary beds on the Murray River near Wellington, S.A. |website=paleodb.org |url=https://paleodb.org/?a=displayReference&reference_no=12134 |url-status=live |archive-url=https://web.archive.org/web/20160318154929/http://fossilworks.org/cgi-bin/bridge.pl?reference_no=12134&action=displayReference |archive-date=18 March 2016 }}
{{Refend}}

== External links ==
{{Commons category|Basilosaurus}}
{{Archaeoceti}}
{{Taxonbar|from=Q134884}}

[[Category:Eocene mammals]]
[[Category:Eocene mammals of North America]]
[[Category:Eocene mammals of Africa]]
[[Category:Basilosauridae]]
[[Category:Transitional fossils]]
[[Category:Prehistoric cetacean genera]]
[[Category:Fossil taxa described in 1834]]
[[Category:Taxa named by Richard Harlan]]
[[Category:Taxa named by Charles William Andrews]]
[[Category:Symbols of Alabama]]
[[Category:Symbols of Mississippi]]
[[Category:Fossil cetaceans misidentified as reptiles]]
[[Category:Eocene mammals of Asia]]
[[Category:Apex predators]]