PBDB Taxon

Basic info	Taxonomic history	Classification	Included Taxa
Morphology	Ecology and taphonomy	External Literature Search	Age range and collections

Helohyus

Mammalia - Helohyidae

Taxonomy

Helohyus was named by Marsh (1872). Its type is Helohyus plicodon.

It was assigned to Helohyinae by Gazin (1955) and Stucky (1998); to Helohyidae by Marsh (1877), Hay (1902), Coombs and Coombs (1977), Carroll (1988), Ferrusquía-Villafranca (2006) and Foss (2007); and to Cetaceamorpha by Spaulding et al. (2009).

Species

H. lentus (syn. Parahyus aberrans), H. milleri (syn. Lophiohyus alticeps), H. plicodon (syn. Thinotherium validum) (type species), Ithygrammodon cameloides, Thinotherium annulatum

Synonyms

Thinotherium was named by Marsh (1872). Its type is Thinotherium validum.

It was synonymized subjectively with Helohyus by Hay (1902).
Ithygrammodon cameloides was named by Osborn et al. (1878) [genotype].

It was considered a nomen dubium by Sinclair (1914) and Stucky (1998).
Lophiohyus was named by Sinclair (1914). It is not extant. Its type is Lophiohyus alticeps.

It was synonymized subjectively with Helohyus by Stucky (1998) and Walsh (2000).

It was assigned to Helohyidae by McKenna and Bell (1997).
Thinotherium was named by Cope (1870) [Marsh used this name for a "new" Eocene artiodactyl genus in 1872; the latter is a junior synonym of Helohyus according to Gazin 1976, Stucky 1998]. Its type is Thinotherium annulatum.

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

It was assigned to Hippopotamidae by Cope (1870); and to Tayassuinae by Hay (1902).

Synonymy list

Year	Name and author
1870	Thinotherium Cope p. 292
1872	Thinotherium Marsh
1872	Helohyus Marsh p. 207
1877	Helohyus Marsh p. 38
1878	Ithygrammodon cameloides Osborn et al. p. 57
1902	Helohyus Hay p. 650
1902	Thinotherium Hay p. 661
1902	Ithygrammodon cameloides Hay p. 674
1914	Lophiohyus Sinclair
1955	Helohyus Gazin p. 37
1977	Helohyus Coombs and Coombs p. 292
1988	Helohyus Carroll p. 639
1997	Lophiohyus McKenna and Bell p. 403
1998	Helohyus Stucky p. 369
2006	Helohyus Ferrusquía-Villafranca p. 995
2007	Helohyus Foss p. 86
2009	Helohyus Spaulding et al.

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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	()

Rank	Name	Author
infraorder	Cynodontia	()
—	Mammaliamorpha
—	Mammaliaformes
class	Mammalia
—	Cladotheria
—	Zatheria
subclass	Tribosphenida	()
subclass	Theria
—	Eutheria	()
—	Placentalia
—	Boreoeutheria
—	Laurasiatheria
—	Scrotifera
—	Euungulata
—	Artiodactylamorpha
—	Artiodactyla	()
superfamily	Dichobunoidea	Gill 1872
family	Helohyidae
genus	Helohyus

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.

G. †Helohyus Marsh 1872

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†Helohyus lentus Marsh 1871

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Invalid names: Parahyus aberrans Marsh 1894 [synonym]

†Helohyus milleri Sinclair 1914

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Invalid names: Lophiohyus alticeps Sinclair 1914 [synonym]

†Helohyus plicodon Marsh 1872

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Invalid names: Thinotherium validum Marsh 1872 [synonym]

Invalid names: Ithygrammodon cameloides Osborn et al. 1878 [nomen dubium], Lophiohyus Sinclair 1914 [synonym], Thinotherium Cope 1870 [synonym], Thinotherium Marsh 1872 [synonym]

Diagnosis

No diagnoses are available