Tethytheria is a clade of mammals 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 proboscideans, as well as the extinct order

Embrithopoda Embrithopoda ("heavy-footed") is an order of extinct mammals known from Asia, Africa and Eastern Europe. Most of the embrithopod genera are known exclusively from jaws and teeth dated from the late Paleocene to the late Eocene; however, the orde ...

. 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 gro ...

of Tethytheria, the interrelationships between the included taxa remain disputed. The tethytheres are united by several characters, including anteriorly facing

orbits In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a p ...

and more or less

bilophodont The molars or molar teeth are large, flat tooth, teeth at the back of the mouth. They are more developed in mammal, mammals. They are used primarily to comminution, grind food during mastication, chewing. The name ''molar'' derives from Latin, ...

cheek teeth (double transverse ridges on the crowns of the teeth). Proboscidea and Sirenia are linked together based on auditory characters in their

petrosal bone The petrous part of the temporal bone is pyramid-shaped and is wedged in at the base of the skull between the sphenoid and occipital bones. Directed medially, forward, and a little upward, it presents a base, an apex, three surfaces, and three an ...

s, but this link may be a

homoplasy Homoplasy, in biology and phylogenetics, is the term used to describe a feature that has been gained or lost independently in separate lineages over the course of evolution. This is different from homology, which is the term used to characterize ...

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 Anthracobunidae is an extinct family of stem perissodactyls that lived in the early to middle Eocene period. They were originally considered to be a paraphyletic family of primitive proboscideans possibly ancestral to the Moeritheriidae and the ...

, 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 †

*** † Phenacolophidae *** †

Arsinoitheriidae Arsinoitheriidae is a family of hoofed mammals belonging to the extinct order Embrithopoda. Remains have been found in the Middle East, Africa, Asia and Romania. When alive, they would have borne a strong but superficial resemblance to modern rh ...

** 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 r ...

***

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 *** † Phosphatheriidae (Numidotheriidae?) *** †

Numidotheriidae Numidotheriidae is an extinct family of primitive proboscidean that lived from the late Paleocene to the early Oligocene periods of North Africa. Fragmentary fossils (mainly teeth) of the early Eocene genera, ''Daouitherium'' and ''Phosphatheri ...

*** †

Moeritheriidae ''Moeritherium'' ("the beast from Lake Moeris") is an extinct genus of primitive proboscideans. These prehistoric mammals are related to the elephant and, more distantly, sea cows and hyraxes. They lived during the Eocene epoch. Description ''M ...

*** †

Barytheriidae Barytheriidae (meaning "heavy beasts") is an extinct family of primitive proboscideans that lived during the late Eocene and early Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to ...

*** †

Deinotheriidae Deinotheriidae ("terrible beasts") is a family of prehistoric elephant-like proboscideans that lived during the Cenozoic era, first appearing in Africa, then spreading across southern Asia (Indo-Pakistan) and Europe. During that time, they cha ...

*** † Palaeomastodontidae *** † Phiomiidae *** † Hemimastodontidae *** †

Mammutidae Mammutidae is an extinct family of proboscideans that appeared during the Oligocene epoch and survived until the start of the Holocene. The family was first described in 1922, classifying fossil specimens of the type genus ''Mammut'' ( masto ...

*** †

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