Tethytheria is a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...

s that includes the

sirenia The Sirenia (), commonly referred to as sea-cows or sirenians, are an order of fully aquatic, herbivorous mammals that inhabit swamps, rivers, estuaries, marine wetlands, and coastal marine waters. The Sirenia currently comprise two distinct ...

ns and

proboscidea The Proboscidea (; , ) are a taxonomic order of afrotherian mammals containing one living family ( Elephantidae) and several extinct families. First described by J. Illiger in 1811, it encompasses the elephants and their close relatives. Fr ...

ns, as well as the extinct order Embrithopoda. Though there is strong anatomical and molecular support for the

monophyly In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic ...

of Tethytheria, the interrelationships between the included taxa remain disputed. The tethytheres are united by several characters, including anteriorly facing orbits and more or less bilophodont cheek teeth (double transverse ridges on the crowns of the teeth). Proboscidea and Sirenia are linked together based on auditory characters in their petrosal bones, but this link may be a homoplasy.

Desmostylia The Desmostylia (from Greek δεσμά ''desma'', "bundle", and στῦλος ''stylos'', "pillar") are an extinct order of aquatic mammals that existed from the early Oligocene (Rupelian) to the late Miocene ( Tortonian) (). Desmostylians are t ...

ns, traditionally considered tethytheres, have been tentatively assigned to Perissodactyla, along with the Early Eocene family Anthracobunidae, which was considered a sister group to Tethytheria.

Systematics

Cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

modified from and .

Classification

Classification modified from . * Clade Tethytheria ** order † Embrithopoda *** † Phenacolophidae *** † Arsinoitheriidae ** order

Sirenia The Sirenia (), commonly referred to as sea-cows or sirenians, are an order of fully aquatic, herbivorous mammals that inhabit swamps, rivers, estuaries, marine wetlands, and coastal marine waters. The Sirenia currently comprise two distinct ...

*** †

Prorastomidae Prorastomidae is a family of extinct sirenians from Jamaica, related to the extant manatees and dugong. The family includes the oldest known fossils of Sirenians, represented in two genera: *''Pezosiren'' ''Pezosiren'' comprises one known species ...

*** †

Protosirenidae Protosirenidae is an extinct primitive family of the order Sirenia. Protosirenids are thought to have been amphibious quadrupeds, meaning that they spent their time both on land and in the water and had four legs. See also *Dugongidae Dugong ...

(Dugongidae?) ***

Dugongidae Dugongidae is a family in the order of Sirenia. The family has one surviving species, the dugong (''Dugong dugon''), one recently extinct species, Steller's sea cow (''Hydrodamalis gigas''), and a number of extinct genera known from fossil reco ...

***

Trichechidae Trichechidae is a family of sirenians that includes all living manatees and several extinct genera. Systematics TRICHECHIDAE *MiosireninaeM. Voss. 2014. On the invalidity of Halitherium schinzii Kaup, 1838 (Mammalia, Sirenia), with comments o ...

** order

Proboscidea The Proboscidea (; , ) are a taxonomic order of afrotherian mammals containing one living family ( Elephantidae) and several extinct families. First described by J. Illiger in 1811, it encompasses the elephants and their close relatives. Fr ...

*** † Phosphatheriidae (Numidotheriidae?) *** † Numidotheriidae *** † Moeritheriidae *** † Barytheriidae *** † Deinotheriidae *** † Palaeomastodontidae *** † Phiomiidae *** †

Hemimastodontidae ''Hemimastodon'' ("half mastodont") is an extinct genus of proboscidean The Proboscidea (; , ) are a taxonomic order of afrotherian mammals containing one living family (Elephantidae) and several extinct families. First described by J. I ...

*** † Mammutidae *** †

Gomphotheriidae Gomphotheres are any members of the diverse, extinct taxonomic family Gomphotheriidae. Gomphotheres were elephant-like proboscideans, but do not belong to the family Elephantidae. They were widespread across Afro-Eurasia and North America dur ...

***

Elephantidae Elephantidae is a family of large, herbivorous proboscidean mammals collectively called elephants and mammoths. These are terrestrial large mammals with a snout modified into a trunk and teeth modified into tusks. Most genera and species in the ...

Notes

References

* * Mammal unranked clades {{afrotheria-stub