PBDB Taxon

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Basilosauridae

Mammalia - Cetacea - Basilosauridae

Taxonomy

Basilosauridae was named by Cope (1867). It was considered paraphyletic by Uhen and Gingerich (2001), Uhen (2004) and Uhen (2008) and Martinez-Cáceres and Muizon (2011).

It was synonymized subjectively with Zeuglodontidae by Mchedlidze (1970).

It was assigned to Zeuglodontia by Gill (1871), Gill (1872) and Gill (1873); to Zeuglodontes by Hay (1902); to Zeuglodonta by Trouessart (1904); to Zeuglodontes by Hay (1930); to Cetacea by Sherman (1952) and Thewissen et al. (2001); to Cetacea by van Vliet (2004); to Archaeoceti by Bouetel and Muizon (2006); to Archaeoceti by Miller (1923), Kellogg (1928), Kellogg (1936), Simpson (1945), Thurmond and Jones (1981), Barnes et al. (1985), Hooker (1986), Carroll (1988), Benton (1993), Fordyce and Barnes (1994), Fordyce et al. (1995), Uhen (1996), Kohler and Fordyce (1997), McKenna and Bell (1997), Bergqvist et al. (1999), Uhen and Gingerich (2001), Fordyce and de Muizon (2001), Rice (2002), Fordyce (2003), Geisler and Sanders (2003), Uhen (2004), Gingerich (2007), McLeod and Barnes (2008), Uhen (2008), Fordyce and Roberts (2009), Fitzgerald (2010), Gingerich (2012), Gingerich and Zouhri (2015), Gingerich (2015) and Gao and Ni (2015); to Basilosauroidea by Rice (1998), Gingerich (2005), Rice (2009), El-kheir et al. (2013) and Mahdy et al. (2019); to Archaeoceti by Bianucci and Landini (2007) and Gingerich et al. (2022); and to Pelagiceti by Uhen (2008), Uhen (2010), Martinez-Cáceres and Muizon (2011), Uhen et al. (2011), Uhen (2013), Goldin et al. (2014), Marx et al. (2016), Buono et al. (2016), Berta (2017), Martínez-Cáceres et al. (2017), Smith et al. (2021), Antar et al. (2023), Bianucci et al. (2023), van Vliet et al. (2023) and van Vliet et al. (2024).

Synonyms

Prozeuglodontidae was named by Moustafa (1954).

It was synonymized subjectively with Basilosauridae by Uhen (2004), Uhen (2013) and Martínez-Cáceres et al. (2017).

It was assigned to Archaeoceti by Moustafa (1954).
Pontogeneus was named by Leidy (1852) [Sepkoski's age data: T Eo-u]. It is not extant.

It was synonymized subjectively with Zeuglodon by Bronn (1853) and Zittel (1894); it was synonymized subjectively with Dorudon by Hay (1902) and Trouessart (1904); it was considered a nomen nudum by Uhen (2005); it was considered a nomen dubium by Martínez-Cáceres et al. (2017).

It was assigned to Archaeoceti by Kellogg (1936); to Cetacea by Sepkoski (2002); to Basilosaurinae by McLeod and Barnes (2008); to Dorudontinae by McKenna and Bell (1997), Uhen (1998), Uhen (2002), Uhen (2004) and Schouten (2011); and to Basilosauridae by Palmer (1904), Thurmond and Jones (1981), Carroll (1988), Cooper et al. (2014), Gingerich (2015) and Berta (2017).
Sulaimanitherium was named by Malkani et al. (2013).

It was considered a nomen dubium by Uhen and Taylor (2020).

It was assigned to Basilosauridae by Malkani et al. (2013) and Malkani (2019).
Sulaimanitherium dhanotri was named by Malkani et al. (2013). Its type specimen is MSID-1 to MSID-100, a set of vertebrae (associated fossilized bones/pieces of bones of vertebral series), and it is a 3D body fossil. Its type locality is Drug Tehsil, which is in a Bartonian coastal shale in the Drazinda Formation of Pakistan.

It was considered a nomen dubium by Uhen and Taylor (2020).
Dorudontidae was named by Miller (1923). It is not extant. Its type is Dorudon. It was considered paraphyletic by Uhen (2008).

It was considered an invalid subgroup of Basilosauridae by Uhen (2013); it was reranked as the subfamily Dorudontinae by Slijper (1936), Fordyce (1982), Barnes et al. (1985), Fordyce and Barnes (1994), Fordyce et al. (1995), Uhen (1996), Kohler and Fordyce (1997), Uhen (1998), Uhen and Gingerich (2001), Uhen (2002), van Vliet (2004), Uhen (2004), Bouetel and Muizon (2006), Bianucci and Landini (2007), McLeod and Barnes (2008), Uhen (2008), Fordyce and Roberts (2009), Uhen (2009), Uhen et al. (2011), Gao and Ni (2015) and Mahdy et al. (2019).

It was assigned to Zeuglodontes by Hay (1930); to Zeuglodontidae by Slijper (1936); to Basilosauroidea by Rice (1998); to Archaeoceti by Miller (1923), Kellogg (1928), Kellogg (1936), Simpson (1945), Keyes (1973), Whitmore and Sanders (1977), Thurmond and Jones (1981), Hooker (1986) and Rice (2002); and to Basilosauridae by Fordyce (1982), Barnes et al. (1985), Fordyce and Barnes (1994), Fordyce et al. (1995), Uhen (1996), Kohler and Fordyce (1997), McKenna and Bell (1997), Uhen (1998), Uhen and Gingerich (2001), Fordyce and de Muizon (2001), Uhen (2002), van Vliet (2004), Uhen (2004), Bouetel and Muizon (2006), Bianucci and Landini (2007), McLeod and Barnes (2008), Uhen (2008), Fordyce and Roberts (2009), Uhen (2009), Uhen et al. (2011), Gao and Ni (2015) and Mahdy et al. (2019).
Zeuglodon wanklyni was named by Seeley (1876) [The species was based on a specimen seen by the author, but never deposited in the BMNH. The specimen has not been seen since.]. Its type specimen is BMNH M. 11090, a skull, and it is a 3D body fossil. Its type locality is Barton Cliff, which is in a Bartonian marine claystone in the Barton Clay Formation of the United Kingdom.

It was recombined as Basilosaurus wanklyni by Trouessart (1904) and Kalmykov (2012); it was recombined as Zygorhiza wanklyni by Kellogg (1936), Hooker (1986) and McLeod and Barnes (2008); it was considered a nomen nudum by Uhen (1996) and Uhen (1998); it was considered an invalid subgroup of Basilosauridae by Gingerich et al. (2022).
Pontogeneus priscus was named by Leidy (1852) [single third or fourth cervical vertebral body]. Its type specimen is ANSP 13668, a set of vertebrae (cervical vertebra), and it is a 3D body fossil. Its type locality is Ouachita River, which is in a Priabonian offshore shelf marl in the Yazoo Formation of Louisiana.

It was synonymized subjectively with Zeuglodon pygmaeus by Bronn (1853); it was synonymized subjectively with Dorudon serratus by Hay (1902) and Trouessart (1904); it was synonymized subjectively with Pontogeneus brachyspondylus by Kellogg (1936) and Thurmond and Jones (1981); it was considered a nomen nudum by Uhen (2005); it was considered a nomen dubium by Martínez-Cáceres et al. (2017).
Zeuglodon brachyspondylus was named by Müller (1849) [North American â€˜Zeuglodonâ€™ brachyspondylus is similar to Masracetus markgrafi , and it may prove to be a species of Masracetus. Z. brachyspondylus was named more than 150 years ago by Mueller (1849: 26) without designation of a holotype, and it has not been studied for many years. To clarify the meaning of the name, the lumbar vertebra illustrated as No. 6 of vertebral series II in Plate XX of Mueller (1849) is designated the lectotype of â€˜Zeuglodonâ€™ brachyspondylus. This was collected by Albert C. Koch in Alabama, and it is now in the collection of the Museum fuer Naturkunde in Berlin. Kellogg (1936: 254) identified the designated vertebra as lumbar L9, and transcribed Muellerâ€™s measurements as 190.5 mm for minimum centrum length; 190.5 mm for anterior centrum width; and 165 mm for anterior centrum height. ANSP 13668 is the type specimen of Pontogeneus priscus, which was subsumed withinin Pontogeneus brachyspondylus]. Its type specimen is MFNB, a set of vertebrae (lumbar vertebra, L9), and it is a 3D body fossil.

It was synonymized subjectively with Basilosaurus serratus by Leidy (1854); it was synonymized subjectively with Zeuglodon cetoides by Lydekker (1887); it was recombined as Basilosaurus brachyspondylus by Hay (1902), Trouessart (1904), Hay (1930) and Sherman (1952); it was recombined as Pontogeneus brachyspondylus by Kellogg (1936), Thurmond and Jones (1981), Uhen (1998), Uhen (2002), Uhen (2004), McLeod and Barnes (2008), Schouten (2011) and Gingerich (2015); it was considered a nomen nudum by Uhen (2005) and Uhen (2009); it was considered a nomen dubium by Martínez-Cáceres et al. (2017).
Balaenoptera juddi was named by Seeley (1881). Its type specimen is BMNH M 133, a set of vertebrae, and it is a 3D body fossil. Its type locality is Roydon, which is in a Priabonian marine horizon in the Headon Hill Formation of the United Kingdom.

It was recombined as Zygorhiza juddi by Kellogg (1936), van Vliet (2004) and McLeod and Barnes (2008); it was considered a nomen nudum by Uhen (1998); it was considered a nomen dubium by Uhen (2013).
Zeuglodontidae was named by Bonaparte (1849). It is not extant.

It was synonymized subjectively with Hydrarchidae by Bonaparte (1850); it was misspelled as Zeuglodontae by Bronn (1853), Lydekker (1887), Cope (1889), Thompson (1890), Cope (1890), Flower and Lydekker (1891), Zittel (1894), Trouessart (1898), Case (1904), Andrews (1906), Stromer (1908), Abel (1914), Abel (1919), Winge (1921), Zittel (1925), Van Deinse (1931), Slijper (1936), Benham (1937) and Mchedlidze (1970); it was synonymized subjectively with Basilosauridae by Hay (1902), Kellogg (1936), Uhen (2004), Uhen (2013) and Martínez-Cáceres et al. (2017).

It was assigned to Cetacea by Bronn (1853); to Pinnipedia by Bonaparte (1849) and Thompson (1890); to Zeuglodonta by Trouessart (1898); to Archaeoceti by Abel (1914), Winge (1921) and Slijper (1936); to Archaeoceti by Benham (1937); and to Archaeoceti by Lydekker (1887), Cope (1889), Cope (1890), Flower and Lydekker (1891), Zittel (1894), Case (1904), Andrews (1906), Stromer (1908), Abel (1919), Zittel (1925), Van Deinse (1931) and Mchedlidze (1970).
Hydrarchidae was named by Bonaparte (1850). Its type is Hydrarchos.

It was synonymized subjectively with Basilosauridae by Kellogg (1936), Uhen (2004), Uhen (2013) and Martínez-Cáceres et al. (2017).

It was assigned to Pinnipedia by Bonaparte (1850).
Stegorhinidae was named by Brandt (1873).

It was synonymized subjectively with Basilosauridae by Kellogg (1936), Uhen (2004), Uhen (2013) and Martínez-Cáceres et al. (2017).

It was assigned to Archaeoceti by Brandt (1873).
Pachycetus humilis was named by Van Beneden (1883) [According to Rothausen (1986), footnote 6, the holotype specimen was in the Zwinger Musueum, Dresden, and probably destroyed during WWII. This appears to be wrong and the specimen still exists.]. It is a 3D body fossil. Its type locality is Helmstedt, which is in a Bartonian/Priabonian marine sandstone in the Gehlberg Formation of Germany.

It was considered a nomen dubium by Kuhn (1935); it was considered a nomen dubium by Uhen and Pyenson (2007); it was considered a nomen nudum by van Vliet et al. (2020); it was considered an invalid subgroup of Basilosauridae by Gingerich et al. (2022).
Hydrarchina was named by Bonaparte (1850). It is extant.

It was synonymized subjectively with Basilosauridae by McKenna and Bell (1997).

It was assigned to Hydrarchidae by Bonaparte (1850).

Synonymy list

Year	Name and author
1849	Zeuglodontidae Bonaparte p. 618
1849	Zeuglodon brachyspondylus Müller pp. pp. 20-33
1850	Hydrarchidae Bonaparte p. 1
1850	Hydrarchina Bonaparte p. 1
1851	Zeuglodon trachyspondylus Koch p. 57
1852	Pontogeneus Leidy
1852	Pontogeneus priscus Leidy p. 52
1853	Zeuglodontae Bronn p. 763
1853	Zeuglodon brachyspondylus Bronn p. 770
1854	Pontogeneus priscus Leidy p. 8
1867	Basilosauridae Cope p. 144
1871	Basilosauridae Gill p. 122
1872	Basilosauridae Gill p. 93
1873	Stegorhinidae Brandt p. 334
1873	Basilosauridae Gill p. 27
1876	Zeuglodon wanklyni Seeley
1881	Balaenoptera juddi Seeley p. 278
1883	Pachycetus humilis Geinitz p. 105
1883	Pachycetus humilis Van Beneden
1887	Balaenoptera juddi Lydekker p. 41
1887	Zeuglodontidae Lydekker p. 49
1889	Zeuglodontidae Cope p. 876
1890	Zeuglodontidae Cope p. 601
1890	Zeuglodon brachyspondylus Cope p. 602
1890	Zeuglodontidae Thompson p. 1
1891	Zeuglodontidae Flower and Lydekker p. 89
1894	Zeuglodontidae Zittel p. 167
1894	Zeuglodon wanklyni Zittel p. 168
1898	Zeuglodontidae Trouessart p. 1009
1898	Zeuglodon brachyspondylus Trouessart p. 1010
1898	Zeuglodon wanklyni Trouessart p. 1010
1898	Balaenoptera juddi Trouessart p. 1077
1898	Pachycetus humilis Trouessart p. 1084
1902	Basilosauridae Hay p. 586
1902	Basilosaurus brachyspondylus Hay p. 586
1903	Zeuglodon wanklyni Stromer p. 87
1904	Zeuglodontidae Case p. 4
1904	Pontogeneus Palmer p. 558
1904	Basilosauridae Trouessart p. 753
1904	Basilosaurus brachyspondylus Trouessart p. 753
1904	Basilosaurus wanklyni Trouessart p. 753
1904	Balaenoptera juddi Trouessart p. 782
1904	Pachycetus humilis Trouessart p. 784
1906	Zeuglodontidae Andrews p. 234
1908	Zeuglodon brachyspondylus Stromer p. 31
1908	Zeuglodontidae Stromer p. 148
1914	Zeuglodon wanklyni Abel p. 220
1914	Zeuglodontidae Abel p. 220
1919	Zeuglodontidae Abel p. 751
1921	Zeuglodontidae Winge p. 7
1923	Dorudontidae Miller
1923	Basilosauridae Miller p. 40
1923	Dorudontidae Miller p. 40
1925	Zeuglodontidae Zittel p. 84
1925	Zeuglodon brachyspondylus Zittel p. 85
1925	Zeuglodon wanklyni Zittel p. 85
1928	Basilosauridae Kellogg p. 32 figs. Table 1
1928	Dorudontidae Kellogg p. 32 figs. Table 1
1930	Basilosauridae Hay p. 569
1930	Basilosaurus brachyspondylus Hay p. 570
1930	Dorudontidae Hay p. 657
1931	Zeuglodontidae Van Deinse p. 33
1936	Zygorhiza juddi Kellogg
1936	Basilosauridae Kellogg p. 13
1936	Dorudontidae Kellogg p. 100
1936	Pontogeneus brachyspondylus Kellogg p. 101
1936	Zygorhiza wanklyni Kellogg p. 176
1936	Pontogeneus Kellogg p. 248
1936	Dorudontinae Slijper p. 540
1936	Zeuglodontidae Slijper p. 540
1937	Zeuglodontidae Benham p. 1
1940	Pachycetus humilis Wetmore p. 72
1945	Basilosauridae Simpson p. 100
1945	Dorudontidae Simpson p. 100
1952	Basilosauridae Sherman p. 99
1952	Basilosaurus brachyspondylus Sherman p. 99
1954	Prozeuglodontidae Moustafa p. 87
1970	Zeuglodontidae Mchedlidze p. 50
1973	Dorudontidae Keyes p. 389
1977	Dorudontidae Whitmore and Sanders p. 305
1981	Dorudontidae Thurmond and Jones p. 192
1981	Basilosauridae Thurmond and Jones p. 193
1981	Pontogeneus Thurmond and Jones p. 196
1981	Pontogeneus brachyspondylus Thurmond and Jones p. 196
1982	Dorudontinae Fordyce p. 422
1985	Basilosauridae Barnes et al. p. 25
1985	Dorudontinae Barnes et al. p. 25
1986	Basilosauridae Hooker p. 214
1986	Dorudontidae Hooker p. 214
1986	Zygorhiza wanklyni Hooker p. 342
1986	Pachycetus humilis Rothausen p. 517
1988	Basilosauridae Carroll
1988	Pontogeneus Carroll
1993	Basilosauridae Benton p. 761
1994	Basilosauridae Fordyce and Barnes p. 428 figs. Table 1
1994	Dorudontinae Fordyce and Barnes p. 428
1995	Basilosauridae Fordyce et al. p. 379
1995	Dorudontinae Fordyce et al. p. 379
1996	Basilosauridae Uhen p. 39
1996	Dorudontinae Uhen p. 41
1997	Basilosauridae Kohler and Fordyce p. 575
1997	Dorudontinae Kohler and Fordyce p. 575
1997	Basilosauridae McKenna and Bell p. 369
1997	Dorudontidae McKenna and Bell p. 369
1997	Pontogeneus McKenna and Bell p. 369
1998	Basilosauridae Rice
1998	Dorudontidae Rice
1998	Dorudontinae Uhen p. 34
1998	Pontogeneus Uhen p. 37
1998	Pontogeneus brachyspondylus Uhen p. 37
1999	Basilosauridae Bergqvist et al. p. 31
2001	Dorudontidae Fordyce and de Muizon p. 104
2001	Basilosauridae Fordyce and de Muizon p. 176
2001	Basilosauridae Thewissen et al. p. 351 figs. Table 1
2001	Basilosauridae Uhen and Gingerich p. 2
2001	Dorudontinae Uhen and Gingerich p. 2
2002	Basilosauridae Rice p. 231 figs. Table 1
2002	Dorudontidae Rice p. 231 figs. Table 1
2002	Pontogeneus Sepkoski
2002	Dorudontinae Uhen p. 79
2002	Pontogeneus Uhen p. 79
2002	Pontogeneus brachyspondylus Uhen p. 79
2003	Basilosauridae Fordyce p. 156 figs. Figure 9.1
2003	Basilosauridae Geisler and Sanders p. 27
2004	Basilosauridae Uhen pp. 11-12
2004	Dorudontinae Uhen p. 12
2004	Pontogeneus Uhen p. 12
2004	Pontogeneus brachyspondylus Uhen p. 12
2004	Basilosauridae van Vliet p. 143
2004	Dorudontinae van Vliet p. 143
2004	Pachycetus humilis van Vliet p. 143
2004	Zygorhiza juddi van Vliet p. 143
2005	Basilosauridae Gingerich p. 237 figs. Table 15.1
2006	Basilosauridae Bouetel and Muizon p. 383
2006	Dorudontinae Bouetel and Muizon p. 383
2007	Basilosauridae Bianucci and Landini p. 45 figs. Table 2.1
2007	Dorudontinae Bianucci and Landini p. 45 figs. Table 2.1
2007	Basilosauridae Gingerich p. 366
2008	Basilosauridae McLeod and Barnes p. 93
2008	Dorudontinae McLeod and Barnes p. 93
2008	Zygorhiza juddi McLeod and Barnes p. 93
2008	Zygorhiza wanklyni McLeod and Barnes p. 93
2008	Pontogeneus McLeod and Barnes p. 94
2008	Pontogeneus brachyspondylus McLeod and Barnes p. 94
2008	Basilosauridae Uhen p. 561
2008	Dorudontinae Uhen p. 561
2008	Basilosauridae Uhen p. 592 figs. Figure 4
2009	Basilosauridae Fordyce and Roberts p. 553
2009	Dorudontinae Fordyce and Roberts p. 553
2009	Basilosauridae Rice p. 235 figs. Table 1
2009	Dorudontinae Uhen p. 93
2010	Basilosauridae Fitzgerald p. 370 figs. Table 1
2010	Basilosauridae Uhen p. 206
2011	Basilosauridae Martinez-Cáceres and Muizon
2011	Pontogeneus Schouten p. 18
2011	Pontogeneus brachyspondylus Schouten p. 18
2011	Dorudontinae Uhen et al. p. 960
2011	Basilosauridae Uhen et al. p. 966 figs. Figure 10
2012	Basilosauridae Gingerich p. 313 figs. Figure 4
2012	Basilosaurus wanklyni Kalmykov p. 179
2013	Basilosauridae El-kheir et al. p. 462
2013	Sulaimanitherium Malkani et al. p. 178 figs. Fig. 1
2013	Sulaimanitherium dhanotri Malkani et al. p. 178 figs. Fig. 1
2013	Basilosauridae Uhen
2014	Pontogeneus Cooper et al. p. 91
2014	Basilosauridae Goldin et al.
2015	Basilosauridae Gao and Ni p. 156 figs. Table 1
2015	Dorudontinae Gao and Ni p. 156 figs. Table 1
2015	Basilosauridae Gingerich p. 164
2015	Pontogeneus Gingerich p. 184
2015	Pontogeneus brachyspondylus Gingerich p. 184
2015	Pontogeneus priscus Gingerich p. 184
2015	Basilosauridae Gingerich and Zouhri p. 278
2016	Basilosauridae Buono et al. p. 299
2016	Basilosauridae Marx et al. p. 101
2017	Basilosauridae Berta p. 159
2017	Pontogeneus Berta p. 159
2017	Basilosauridae Martínez-Cáceres et al. p. 11
2019	Basilosauridae Mahdy et al.
2019	Dorudontinae Mahdy et al.
2019	Sulaimanitherium Malkani p. 920
2019	Sulaimanitherium dhanotri Malkani p. 920
2021	Basilosauridae Smith et al.
2022	Basilosauridae Gingerich et al. p. 12
2023	Basilosauridae Antar et al. p. 2
2023	Basilosauridae Bianucci et al.
2023	Basilosauridae van Vliet et al. p. 7
2024	Basilosauridae van Vliet et al. p. 6

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Rank	Name	Author
kingdom	Animalia	()
—	Bilateria
—	Eubilateria	Ax 1987
—	Deuterostomia
phylum	Chordata	Haeckel 1874
subphylum	Vertebrata
superclass	Gnathostomata
—	Osteichthyes	()
subclass	Sarcopterygii	()
subclass	Dipnotetrapodomorpha	(Nelson 2006)
subclass	Tetrapodomorpha	()
—	Tetrapoda
—	Reptiliomorpha
—	Anthracosauria
subclass	Amphibiosauria	Kuhn 1967
—	Cotylosauria	()
—	Amniota
subclass	Synapsida
—	Therapsida	()
infraorder	Cynodontia	()
—	Mammaliamorpha
—	Mammaliaformes

Rank	Name	Author
class	Mammalia
—	Theriamorpha	(Rowe 1993)
—	Theriiformes	()
—	Trechnotheria
—	Cladotheria
—	Zatheria
subclass	Tribosphenida	()
subclass	Theria
—	Eutheria	()
—	Placentalia
—	Boreoeutheria
—	Laurasiatheria
—	Scrotifera
—	Euungulata
—	Artiodactylamorpha
—	Artiodactyla	()
—	Whippomorpha
order	Cetacea
—	Pelagiceti
family	Basilosauridae
family	Basilosauridae

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

Fm. †Basilosauridae Cope 1867

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G. †Ancalecetus Gingerich and Uhen 1996

†Ancalecetus simonsi Gingerich and Uhen 1996

Subfm. †Basilosaurinae Miller 1923

Invalid names: Zeuglodontinae Slijper 1936 [synonym]

G. †Basilosaurus Harlan 1834

†Basilosaurus cetoides Owen 1839

Invalid names: Alabamornis gigantea Abel 1906 [synonym], Hydrarchos sillimani Wyman 1845 [synonym], Hydrargos sillimanii Koch 1845 [synonym], Zeuglodon ceti Wyman 1845 [synonym], Zeuglodon harlani De Kay 1842 [synonym], Zeuglodon macrospondylus Müller 1849 [synonym]

†Basilosaurus isis Andrews 1904

Invalid names: Alabamornis Abel 1906 [synonym], Basilosaurus puschi Brandt 1873 [nomen dubium], Hydrarchos Koch 1845 [synonym], Hydrarchus Muller 1849 [synonym], Hydrargos Koch 1845 [synonym], Zeuglodon Owen 1839 [objective synonym], Zugodon Scudder 1882 [synonym], Zygodon Owen 1839 [synonym]

G. †Basiloterus Gingerich et al. 1997

†Basiloterus hussaini Gingerich et al. 1997

G. †Chrysocetus Uhen and Gingerich 2001

†Chrysocetus fouadassii Gingerich and Zouhri 2015

†Chrysocetus healyorum Uhen and Gingerich 2001

G. †Cynthiacetus Uhen 2005

†Cynthiacetus maxwelli Uhen 2005

†Cynthiacetus peruvianus Martinez-Cáceres and Muizon 2011

G. †Dorudon Gibbes 1845

†Dorudon atrox Andrews 1906

Invalid names: Dorudon intermedius Dart 1923 [synonym], Dorudon stromeri Kellogg 1928 [synonym]

†Dorudon serratus Gibbes 1845

Invalid names: Prozeuglodon Andrews 1906 [synonym]

G. †Masracetus Gingerich 2007

†Masracetus markgrafi Gingerich 2007

G. †Ocucajea Uhen et al. 2011

†Ocucajea picklingi Uhen et al. 2011

Subfm. †Pachycetinae Gingerich et al. 2022

G. †Antaecetus Gingerich et al. 2022

†Platyosphys aithai Gingerich and Zouhri 2015

G. †Pachycetus Van Beneden 1883

†Pachycetus paulsonii Brandt 1873

Invalid names: Basilotritus uheni Goldin and Zvonok 2013 [synonym], Pachycetus robustus Van Beneden 1883 [synonym], Platyosphys einori Gritsenko 2001 [synonym], Zeuglodon rossicus Paulson in Brandt 1873 [synonym]

†Pachycetus wardii Uhen 1999

Invalid names: Basilotritus Goldin and Zvonok 2013 [synonym], Platyosphys Kellogg 1936 [synonym]

G. †Perucetus Bianucci et al. 2023

†Perucetus colossus Bianucci et al. 2023

G. †Saghacetus Gingerich 1992

†Saghacetus osiris Dames 1894

Invalid names: Dorudon elliotsmithii Dart 1923 [synonym], Dorudon sensitivus Dart 1923 [synonym], Dorudon zitteli Stromer 1903 [synonym]

G. †Stromerius Gingerich 2007

†Stromerius nidensis Gingerich 2007

G. †Supayacetus Uhen et al. 2011

†Supayacetus muizoni Uhen et al. 2011

G. †Tutcetus Antar et al. 2023

†Tutcetus rayanensis Antar et al. 2023

G. †Zygorhiza True 1908

†Zygorhiza kochii Carus 1847

Invalid names: Zeuglodon brachyspondylum Abel 1914 [synonym], Zeuglodon hydrarchus Carus 1849 [synonym], Zygorhiza brachyspondylus True 1908 [synonym], Zygorhiza minor True 1908 [synonym]

Invalid names: Balaenoptera juddi Seeley 1881 [nomen dubium], Dorudontinae Miller 1923 [invalid subgroup], Hydrarchidae Bonaparte 1850 [synonym], Hydrarchina Bonaparte 1850 [synonym], Pachycetus humilis Van Beneden 1883 [invalid subgroup], Pontogeneus Leidy 1852 [nomen dubium], Pontogeneus brachyspondylus Müller 1849 [nomen dubium], Prozeuglodontidae Moustafa 1954 [synonym], Stegorhinidae Brandt 1873 [synonym], Stromeriinae Gingerich 2007 [empty], Sulaimanitherium Malkani et al. 2013 [nomen dubium], Zeuglodontidae Bonaparte 1849 [synonym]

Diagnosis

Reference	Diagnosis
M. D. Uhen 2004	Members of the Basilosauridae lack M3 and sacral vertebrae.. Basilosaurids have accessory denticles on their adult premolars and molars and have a very reduced hindlimb. Members of the other families of archaeocetes, Protocetidae, Remingtonocetidae, and Ambulocetidae retain M3, have sacral vertebrae, and have large hind limbs. They also lack accessory denticles on their adult cheek teeth.
M. D. Uhen 2008	Basilosauridae are distinguished from all other archaeocetes by: the loss of M3, the presence of multiple accessory denticles on the cheek teeth, loss of the sacrum, reduction of the hind limb, and rotation of the pelvis (Uhen, 1998a).
M. D. Uhen 2013	Members of the family Basilo- sauridae possess two upper molars rather than the three typical of other archaeocetes, as well as multiple acces- sory denticles on their cheek teeth. Most basilosaurids also have longer bodies than other archaeocetes due to an increased numbers of thoracic and lumbar vertebrae. The thoracic vertebral count is 16 in Basilosaurus (Bebej et al., 2012), 20 in Cynthiacetus (Martínez-Cáceres and de Muizon, 2011), 17 in Dorudon (Uhen, 2004) and Zygorhiza (pers. obs. contra (Kellogg, 1936)). The complete thorac- ic count is unknown for Ancalecetus (probably 17, see Gin- gerich and Uhen, 1996 for discussion), Chrysocetus (at least 13), Masracetus, Ocucajea, Saghacetus (at least 15, pers. obs.). The thoracic vertebral count for Stromerius and Supayace- tus are unknown. The exception to this generalization is Basilotritus wardii, which has a thoracic vertebral count of 12 (Uhen, 2001), more similar to the thoracic count of protocetids than other basilosaurids (Uhen et al., 2011). The lumbar vertebral count is 16 in Cynthiacetus (Martínez-Cáceres and de Muizon, 2011), 20 in Basilosau- rus (Gingerich et al., 1990) and Dorudon, (Uhen, 2004). The lumbar vertebral count is unknown for Basilotritus (Gol’din and Zvonok, 2013). All basilosaurids also have forelimbs modified into flippers. These forelimbs include: a fan shaped scapular blade; robust humerus, radius and ulna; elbow joints with limited rotation (which exclude the ability to pronate and supinate the forearm); and car- pal joints which also limit a wide range of motion. In basi- losaurids for which they are known (Basilosaurus (Lucas, 1900; Gingerich et al., 1990), Chrysocetus (Uhen and Gin- gerich, 2001), and Dorudon (Uhen, 2004)), the hindlimbs are greatly reduced and do not retain a bony connection to the vertebral column. The innominate of Basilotritus is not as reduced as those of other basilosaurids (see Uhen, 1999). See Uhen (1998, 2009) for thorough discussions of basilosaurid characteristics.
M. Martínez-Cáceres et al. 2017	Basilosaurids are medium-to-large sized archaeocetes characterized principally by: 1) a at palate narrowing at the level of P4; 2) absence of M3; 3) anterior edge of the orbit dorsal to the level of P4 or P4/M1 diastema; 4) anterior process of the periotic strongly elliptical in cross-section; 5) triangular expan- sion on the posterolateral corner of the pars cochlearis; and 6) well developed ventrolateral tuberosity of the periotic.
P. D. Gingerich et al. 2022	Basilosaurids are middle and late Eocene cetaceans that differ from earlier Pakicetidae, Ambu- locetidae, and Protocetidae in lacking upper third molars. They also differ in having well- developed pterygoid sinuses that separate left and right middle and inner ears acoustically, short cervical vertebrae, augmented numbers of thoracic and lumbar vertebrae, forelimbs modified into flippers, and hind limbs reduced in size and no longer articulating with the ver- tebral column. Basilosaurids were the first whales to become fully aquatic. Basilosaurids differ from later odontocetes and mysticetes in retaining a dental formula of 3.1.4.2 / 3.1.4.3 with recognizable upper and lower incisor, canine, premolar, and molar teeth. Skulls are not telescoped. There is no evidence of baleen. Basilosaurids retain forelimbs with a moveable elbow, and retain hind limbs with reduced but recognizable innominate, femur, tibia, fibula, ankle, and foot bones. Development of a tail fluke is questionable.