Holotheria

Holotheria is a diverse group of mammals that are descendants of the last common ancestor of Kuehneotherium (now known to be a non-mammalian cynodont) and Theria (the group that includes marsupials and placental mammals). The group is characterized by the beginning of the triangulation of a typical triconodont dentition in morganucodonts, towards a symmetrodonta. This triangulation occurs convergently in Docodontiformes although Shuotheriidae was formerly considered sister to Australosphenida. There are studies that place Docodonta as sister to Monotremata, which would make Docodontiformes fall within Pan-Monotremata instead of being a clade outside Holotheria.

Holotheria fell into disuse and was widely considered invalid by the early 2000s, but Mao et al. in 2024 revived the clade due to them finding Allotheria (the group containing multituberculates and their relatives) outside crown group of mammals.

Classification

According to McKenna/Bell (1997):

• Class Mammalia Subclass Theriiformes Infraclass Holotheria Genus †Chronoperates? Superlegion †Kuehneotheria Genus †Woutersia Family †Kuehneotheriidae Superlegion Trechnotheria Legion †Symmetrodonta* Genus †Casamiquelia? Genus †Thereuodon? Genus †Atlasodon? Genus †Eurylambda? Genus †Peralestes? Genus †Shuotherium? Order †Amphidontoidea Family †Amphidontidae Order †Spalacotherioidea Genus †Gobiotheriodon? Genus †Maotherium Genus †Zhangheotherium Family †Tinodontidae Family †Barbereniidae? Genus †Guirogatherium? Genus †Barberenia? Family †Spalacotheriidae Genus †Microderson Genus †Shalbaatar Genus †Spalacotherium Subfamily †Spalacolestinae Genus †Symmetrolestes Genus †Akidolestes Genus †Heishanlestes Genus †Spalacotheroides Genus †Spalacotheridium Genus †Spalacolestes Genus †Symmetrodontoides Legion Cladotheria Genus †Butlerigale? Family †Ausktribosphenidae? Sublegion †Dryolestoidea Order †Dryolestida Order †Amphitheriida Sublegion Zatheria Infralegion †Peramura Infralegion Tribosphenida Genus †Ambondro? Genus †Hypomylos? Genus †Montanalestes? Genus †Tribactonodon? Supercohort †Aegialodontia Family †Aegialodontidae Genus †Aegialodon Genus †Kielantherium Supercohort Theria Order †Deltatheroida Order †Asiadelphia Cohort Marsupialia Magnorder Australidelphia Superorder Microbiotheria Superorder Eometatheria Order †Yalkaparidontia Order Notoryctemorphia Grandorder Dasyuromorphia Grandorder Syndactyli Order Peramelia Order Diprotodontia Magnorder Ameridelphia Cohort Placentalia Order †Bibymalagasia Magnorder Xenarthra Magnorder Epitheria

According to Wang, Clemens, Hu & Li, 1998

• Class Mammalia Subclass Theriiformes Infraclass Holotheria Genus †Chronoperates? Superlegion †Kuehneotheria Superlegion Trechnotheria Family †Amphidontidae Superfamily †Spalacotheroidea Legion Symmetrodonta Genus †Asfaltomylos? Genus †Atlasodon? Family †Ausktribosphenidae? Genus †Casamiquelia? Genus †Thereuodon? Genus †Eurylambda? Genus †Shuotherium Legion Cladotheria Genus †Butlerigale? Sublegion †Dryolestoidea Order †Dryolestida Order †Amphitheriida Genus †Amphitherium Sublegion Zatheria Genus †Arguitherium? Genus †Arguimus? Genus †Nanolestes? Genus †Vincelestes? Infralegion †Peramura Infralegion Tribosphenida