PBDB Taxon

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Pachycetus paulsonii

Osteichthyes - Cetacea - Basilosauridae

Taxonomy

Zeuglodon paulsonii was named by Brandt (1873) [The type specimen is in the Anatomical Museum of the University of Kiev according to Kellogg (1936): no number is available. See Brandt 1873b, plate 34. The holotype of Platyosphys paulsonii is not available for study at present. In 1920s it was probably relocated from the Anatomical Museum of Kiev University (now National Museum of Medicine of Ukraine) to the university itself, and it was never recorded or seen after the World War II. Thus, this type specimen is considered to be lost, and the name Platyosphys paulsonii is considered as nomen dubium (Gol'din & Zvonok 2013). ]. Its type specimen is no number listed, a set of vertebrae, and it is a 3D body fossil. Its type locality is Chigirin, which is in a Priabonian marine claystone in Ukraine.

It was recombined as Basilosaurus paulsoni by Trouessart (1904), Dubrovo and Kapelist (1979); it was recombined as Platyosphys paulsonii by Kellogg (1936), Gingerich and Zouhri (2015), van Vliet et al. (2019); it was recombined as Platyosphys paulsoni by Mchedlidze (1970), van Vliet (2004); it was considered a nomen dubium by Uhen (2013), Goldin and Zvonok (2013); it was recombined as Pachycetus paulsonii by van Vliet et al. (2020), Gingerich et al. (2022), van Vliet et al. (2025).

Sister species lacking formal opinion data

P. paulsoni, P. paulsoni

Synonyms

Zeuglodon rossicus was named by Paulson in Brandt (1873). It is a 3D body fossil.

It was corrected as Zeuglodon rossicum by Abel (1914); it was synonymized subjectively with Platyosphys paulsonii by Kellogg (1936), Mchedlidze (1970); it was synonymized subjectively with Pachycetus paulsonii by Gingerich et al. (2022).
Basilotritus uheni was named by Goldin and Zvonok (2013). Its type specimen is NMNH-P OF-2096, a partial skeleton (left tympanic bulla, three posterior thoracic vertebrae (one sub- complete and two centra) and a rib fragment), and it is a 3D body fossil. Its type locality is Beloskelevatoye, which is in a Bartonian marine siltstone in the Kiev Formation of Ukraine.

It was recombined as Platyosphys uheni by Gingerich and Zouhri (2015), van Vliet et al. (2019); it was recombined as Pachycetus uheni by van Vliet et al. (2020); it was synonymized subjectively with Pachycetus paulsonii by Gingerich et al. (2022).
Pachycetus robustus 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.]. Its type specimen is NsT90, NsT91, NsT93, NsT94, a partial skeleton, and 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 is the type species of Pachycetus.

It was considered a nomen dubium by Kuhn (1935); it was considered a nomen dubium by Uhen and Pyenson (2007); it was synonymized subjectively with Pachycetus paulsonii by Gingerich et al. (2022).
Platyosphys einori was named by Gritsenko (2001). It is a 3D body fossil. Its type locality is Pyrohiv Quarry, which is in a Priabonian marine horizon in the Obukhiv Formation of Ukraine.

It was considered a nomen dubium by Uhen (2013), Goldin and Zvonok (2013); it was synonymized subjectively with Pachycetus paulsonii by Gingerich et al. (2022).

Synonymy list

Year	Name and author
1873	Zeuglodon paulsonii Brandt
1873	Zeuglodon rossicus Paulson in Brandt p. 336
1883	Pachycetus robustus Geinitz p. 105
1883	Pachycetus robustus Van Beneden
1894	Zeuglodon paulsoni Zittel p. 168
1898	Zeuglodon paulsonii Trouessart p. 1010
1898	Pachycetus robustus Trouessart p. 1054
1904	Basilosaurus paulsoni Trouessart p. 753
1904	Pachycetus robustus Trouessart p. 784
1914	Zeuglodon rossicum Abel p. 203
1936	Platyosphys paulsonii Kellogg p. 97
1940	Pachycetus robustus Wetmore p. 72
1970	Platyosphys paulsoni Mchedlidze p. 52
1979	Basilosaurus paulsoni Dubrovo and Kapelist p. 12
1986	Pachycetus robustus Rothausen p. 517
1997	Pachycetus robustus Gingerich et al. p. 68
2001	Platyosphys einori Gritsenko p. 17
2004	Pachycetus robustus van Vliet p. 143
2004	Platyosphys paulsoni van Vliet p. 143
2013	Basilotritus uheni Goldin and Zvonok p. 255 figs. Fig. 3-6
2013	Basilotritus uheni Uhen p. 7
2014	Basilotritus uheni Goldin et al.
2015	Platyosphys einori Gingerich and Zouhri p. 280
2015	Platyosphys paulsonii Gingerich and Zouhri p. 280
2015	Platyosphys uheni Gingerich and Zouhri p. 280
2018	Basilotritus uheni Uhen
2019	Platyosphys paulsonii van Vliet et al. p. 110
2019	Platyosphys uheni van Vliet et al. p. 110
2020	Pachycetus paulsonii van Vliet et al. p. 123
2020	Pachycetus robustus van Vliet et al. p. 124
2020	Pachycetus uheni van Vliet et al. p. 132
2022	Pachycetus paulsonii Gingerich et al. p. 16
2025	Pachycetus paulsonii van Vliet et al. p. 215

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

Rank	Name	Author
—	Mammaliaformes
class	Mammalia
—	Cladotheria
—	Zatheria
subclass	Tribosphenida	()
subclass	Theria
—	Eutheria	()
—	Placentalia
—	Boreoeutheria
—	Laurasiatheria
—	Scrotifera
—	Euungulata
—	Artiodactylamorpha
—	Artiodactyla	()
—	Whippomorpha
order	Cetacea
—	Pelagiceti
family	Basilosauridae
subfamily	Pachycetinae
genus	Pachycetus
species	paulsonii	()

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.

†Pachycetus paulsonii Brandt 1873

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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]

Diagnosis

Reference	Diagnosis
P. D. Gingerich et al. 2022	Pachycetus paulsonii differs from Pachycetus wardii in being significantly larger. Lumbar centra with epiphyses average 266 mm in length for P. paulsonii and average 171 mm in length for P. wardii—a difference of 0.44 units on a natural-log scale, which for a linear measurement is equivalent to a difference of about 8 standard deviations.
H. J. van Vliet et al. 2025	Premolars and molars with a well-developed, crenulated cingulum with multiple tubercles on the distal edge of the crown, forming a ring around the most basal accessory denticle; premolars with four denticles with little ‘second order’ denticles; enamel with coarse striations at the lingual side and somewhat less coarse striations at the labial one. Cervical vertebrae relatively longer than in derived basilosaurids. Post-cervical vertebrae large and having a width larger than the height. In thoracic vertebrae. the posterior width and height exceed the anterior width and height, and neural arches with large post-zygapophyses. Elongated torso vertebrae with elongated transverse rocesses and pedicles of the neural arch, pachyosteoscle- rosis of the pedicles, and centra having a circumferential, compact, multilayered cortex with elongated punctae.

Measurements

No measurements are available

Composition:

hydroxyapatiteo

Form:

roller-shapedo

Ontogeny:

modification of partso

Environment:

marineo

Locomotion:

actively mobileo

Life habit:

aquatico

Depth habitat:

surfaceo

Diet:

carnivoreo

Reproduction:

viviparouso

Created:

2005-03-06 14:19:05

Modified:

2017-04-17 10:41:18

Source: o = order

Reference: Uhen 2004

Age range: base of the Bartonian to the top of the Priabonian or 41.03000 to 33.90000 Ma

Collections (27 total)

Time interval	Ma	Country or state	Original ID and collection number
Eocene	56.0 - 33.9	Russian Federation	Archaeoceti indet. (114208)
Eocene	56.0 - 33.9	Ukraine	Basilosaurus sp. (132383 132385 132389 132391) Zeuglodon sp. (132386)
Lutetian - Bartonian	48.07 - 37.71	Peru (Ica)	Protocetidae indet. (73780)
Middle Eocene - Oligocene	48.07 - 23.04	Netherlands	Archaeoceti indet. (82994)
Bartonian	41.03 - 37.71	Russian Federation	Basilosaurus sp., Eocetus sp. (123876)
Bartonian	41.03 - 37.71	Ukraine (Luhansk)	Basilotritus uheni, Basilosauridae indet. (132393)
Bartonian	41.03 - 37.71	Ukraine	Eocetus sp. (137757)
Bartonian	41.03 - 37.71	Ukraine (Kirovograd)	Basilosauridae indet. (132381)
Bartonian	41.03 - 37.71	Germany (Lower Saxony)	Pachycetus sp. (211071 211080)
Bartonian	41.03 - 37.71	Germany (Bavaria)	Eocetus sp. (71821)
Bartonian	41.03 - 37.71	Netherlands	Archaeoceti indet. (227706) Pachycetus paulsonii (168386)
Bartonian - Priabonian	41.03 - 33.9	Germany	Pachycetus robustus (46086)
Bartonian - Priabonian	41.03 - 33.9	Germany (Lower Saxony)	Pachycetus sp. (211074 211075)
Priabonian	37.71 - 33.9	Ukraine (Kiev)	Zeuglodon paulsonii (type locality: 48026)
Priabonian	37.71 - 33.9	Ukraine	Platyosphys paulsonii (48027) Zeuglodon paulsonii (48028)
Priabonian	37.71 - 33.9	Germany	Pachycetus sp. (211084)
Priabonian	37.71 - 33.9	Germany (Lower Saxony)	Pachycetus sp. (211078)
Priabonian	37.71 - 33.9	Ukraine (Kyiv)	Platyosphys einori (57767)
Priabonian	37.71 - 33.9	Russian Federation	Zeuglodon paulsonii (77227)