# Were There Any Other Mammals Other Than Present Three Groups? **URL:** \ **Category:** Factual Questions\ **Created:** [March 28, 2011, 10:45pm UTC](https://boards.straightdope.com/t/were-there-any-other-mammals-other-than-present-three-groups/576323 "2011-03-28T22:45:24Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Markxxx](https://avatars.discourse-cdn.com/v4/letter/m/5daacb/32.png) [@Markxxx](https://boards.straightdope.com/u/Markxxx)\ **Post date:** [March 28, 2011, 10:45pm UTC](https://boards.straightdope.com/t/were-there-any-other-mammals-other-than-present-three-groups/576323/1 "2011-03-28T22:45:24Z")
Mammals today can be divided into three groups Monotremes (Platypus and the Echidna) Marsupials (Kangaroos, Opossums, Koalas) The Placentals (Humans, etc) I was wondering in the past, if there have been any other type of mammals that don’t fit into one of these three groups? ---
**Author:** ![Bosda\_Di\_Chi\_of\_Tricor](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bosda_di_chi_of_tricor/32/16845_2.png) [@Bosda\_Di\_Chi\_of\_Tricor](https://boards.straightdope.com/u/Bosda_Di_Chi_of_Tricor)\ **Post date:** [March 28, 2011, 10:58pm UTC](https://boards.straightdope.com/t/were-there-any-other-mammals-other-than-present-three-groups/576323/2 "2011-03-28T22:58:29Z")
There were Reptomammals, long ago. ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [March 28, 2011, 11:03pm UTC](https://boards.straightdope.com/t/were-there-any-other-mammals-other-than-present-three-groups/576323/3 "2011-03-28T23:03:51Z")
> **[Allotheria](https://en.wikipedia.org/wiki/Allotheria)** > > Allotheria (meaning "other beasts", from the Greek αλλός, allos–other and θήριον, therion–wild animal) is an extinct clade of mammals known from the Mesozoic and early Cenozoic. Shared characteristics of the group are the presence of lower molariform teeth equipped with longitudinal rows of cusps and enlarged incisors. Typically, the canine teeth are also lost. Allotheria includes Multituberculata, Gondwanatheria (which may be part of Multituberculata, as the sister group to Cimolodonta) Zofia ... > **[Prototheria](https://en.wikipedia.org/wiki/Prototheria)** > > Prototheria (/ˌproʊtəˈθɪəriə, -toʊ-/; from Greek πρώτος, prōtos, first, + θήρ, thēr, wild animal) is an obsolete subclass of mammals which includes the living Monotremata and to which variety of extinct groups, including Morganucodonta, Docodonta, Triconodonta and Multituberculata have also been assigned. It is today no longer considered a valid grouping, but a paraphyletic evolutionary grade of basal mammals and mammaliaform cynodonts. > Most of the animals in this group are extinct. The egg-layi... > **[Theria](https://en.wikipedia.org/wiki/Theria)** > > Theria (/ˈθɪəriə/; Greek: θηρίον theríon, wild beast) is a subclass of mammals amongst the Theriiformes. Theria includes the eutherians (including the placental mammals) and the metatherians (including the marsupials) but excludes the egg-laying monotremes and various extinct mammals evolving prior to the common ancestor of placentals and marsupials. > Therian mammals give birth (see viviparity) to live young without a shelled egg. This is possible thanks to key proteins called syncytins which a... ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [March 28, 2011, 11:29pm UTC](https://boards.straightdope.com/t/were-there-any-other-mammals-other-than-present-three-groups/576323/4 "2011-03-28T23:29:06Z")
[Triconodonta](http://en.wikipedia.org/wiki/Triconodonta) also. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [March 29, 2011, 1:42am UTC](https://boards.straightdope.com/t/were-there-any-other-mammals-other-than-present-three-groups/576323/5 "2011-03-29T01:42:28Z")
During the Mesozoic, there were a variety of mammalian groups whose relationship to the modern three groups is uncertain. The best known of these groups is the [multituberculates](http://en.wikipedia.org/wiki/Multituberculata), rodent-like animals that originated in the Jurassic and survived to the Oligocene. ---
**Author:** ![El\_Presidente](https://avatars.discourse-cdn.com/v4/letter/e/c2a13f/32.png) [@El\_Presidente](https://boards.straightdope.com/u/El_Presidente)\ **Post date:** [March 29, 2011, 5:54am UTC](https://boards.straightdope.com/t/were-there-any-other-mammals-other-than-present-three-groups/576323/6 "2011-03-29T05:54:19Z")
Russell Brand.