Castorocauda is an extinct, semi-aquatic, superficially otter-like genus of docodont mammaliaforms with one species, C. lutrasimilis. It is part of the Yanliao Biota, found in the Daohugou Beds of Inner Mongolia, China dating to the Middle to Late Jurassic. It was part of an explosive Middle Jurassic radiation of Mammaliaformes moving into diverse habitats and niches. Its discovery in 2006, along with the discovery of other unusual mammaliaforms, disproves the previous hypothesis of Mammaliaformes remaining evolutionarily stagnant until the extinction of the non-avian dinosaurs.
Docodonta is an order of extinct Mesozoic mammaliaforms. They were among the most common mammaliaforms of their time, persisting from the Middle Jurassic to the Early Cretaceous across the continent of Laurasia. They are distinguished from other early mammaliaforms by their relatively complex molar teeth. Docodont teeth have been described as "pseudotribosphenic": a cusp on the inner half of the upper molar grinds into a basin on the front half of the lower molar, like a mortar-and-pestle. This is a case of convergent evolution with the tribosphenic teeth of therian mammals. There is much uncertainty for how docodont teeth developed from their simpler ancestors. Their closest relatives may have been certain Triassic "symmetrodonts", namely Woutersia, Delsatia, and Tikitherium.
Mammaliaformes is a clade that contains the crown group mammals and their closest extinct relatives; the group radiated from earlier probainognathian cynodonts. It is defined as the clade originating from the most recent common ancestor of Morganucodonta and the crown group mammals; the latter is the clade originating with the most recent common ancestor of extant Monotremata, Marsupialia, and Placentalia. Besides Morganucodonta and the crown group mammals, Mammaliaformes includes Docodonta and Hadrocodium as well as the Triassic Tikitherium, the earliest known member of the group.
Docodon is an extinct docodont mammaliaform from the Late Jurassic of western North America. It was the first docodont to be named.
Shuotherium is a fossil mammaliaform known from Middle-Late Jurassic of the Forest Marble Formation of England, and the Shaximiao Formation of Sichuan, China.
Anoualerpeton is an extinct genus of lissamphibian in the family Albanerpetontidae. It is the oldest and most primitive albanerpetontid known. Fossils have been found of two different species, Anoualerpeton priscus from the Middle Jurassic (Bathonian) aged Forest Marble and Kilmaluag formations of England and Scotland, and Anoualerpeton unicus from Late Jurassic-Early Cretaceous (Tithonian-Berriasian) Ksar Metlili Formation of Morocco. A. unicus is the only named albanerpetontid from Gondwana.
Paritatodon is an extinct mammaliaform which existed in Kyrgyzstan and England during the Jurassic period. It was originally the holotype specimen of Shuotherium kermacki, but Martin and Averianov (2010) argued that it resembled the genus Itatodon (Docodonta) and so renamed it Paritatodon.
Several mammals are known from the Mesozoic of Madagascar. The Bathonian Ambondro, known from a piece of jaw with three teeth, is the earliest known mammal with molars showing the modern, tribosphenic pattern that is characteristic of marsupial and placental mammals. Interpretations of its affinities have differed; one proposal places it in a group known as Australosphenida with other Mesozoic tribosphenic mammals from the southern continents (Gondwana) as well as the monotremes, while others favor closer affinities with northern (Laurasian) tribosphenic mammals or specifically with placentals. At least five species are known from the Maastrichtian, including a yet undescribed species known from a nearly complete skeleton that may represent a completely new group of mammals. The gondwanathere Lavanify, known from two teeth, is most closely related to other gondwanatheres found in India and Argentina. Two other teeth may represent another gondwanathere or a different kind of mammal. One molar fragment is one of the few known remains of a multituberculate mammal from Gondwana and another has been interpreted as either a marsupial or a placental.
Haldanodon is an extinct docodont mammaliaform which lived in the Upper Jurassic. Its fossil remains have been found in Portugal, in the well-known fossil locality of Guimarota, which is in the Alcobaça Formation. It may have been a semi-aquatic burrowing insectivore, similar in habits to desmans and the platypus. Several specimens are known, include a partial skeleton and well-preserved skulls.
The Kilmaluag Formation is a Middle Jurassic geologic formation in Scotland. It was formerly known as the Ostracod Limestone for preserving an abundance of fossil freshwater/low salinity ostracods. Gastropods, bivalves, trace fossil burrows, and vertebrate fossil remains have also been recorded from the formation. Vertebrate fossils include fish, crocodylomorphs, mammals, small reptiles, amphibians, theropod and sauropod dinosaurs and pterosaurs.
Tashkumyrodon is an extinct mammaliaform from the Middle Jurassic (Callovian) Balabansai Formation of Kyrgyzstan It is named after the town of Tash-Kömür, near where the original specimen was found. It belongs to the order Docodonta and is closely related to Sibirotherium and Tegotherium. There is only one species currently known, Tashkumyrodon desideratus.
Borealestes is a genus of docodontan from the Middle Jurassic of Britain, first discovered on the Isle of Skye near the village of Elgol. It was the earliest mammaliaform from the Mesozoic found and named in Scotland. A second species and was later found in other Middle Jurassic sites in England, but is now shown to be a different genus. A new species, B. cuillinensis was named in 2021, also from Skye.
Wareolestes rex is a mammaliaform from the Middle Jurassic (Bathonian) rocks of England and Scotland. It was originally known from isolated teeth from England, before a more complete jaw with teeth was found in the Kilmaluag Formation of Skye, Scotland.
Palaeoxonodon is an extinct genus of cladotherian mammal from the Middle Jurassic of England and Scotland.
Peraiocynodon is an extinct mammaliaform from the order Docodonta, found in the Middle Jurassic rocks of the United Kingdom. It is only known from isolated molar teeth found in the mammal bed at Kirtlington cement quarry in Oxfordshire, England.
Cyrtlatherium is a dubious genus of extinct docodontan mammaliaform from the Middle Jurassic rocks of Oxfordshire, England. As it is only known from a few isolated molar teeth, there is disagreement about whether Cyrtlatherium is a separate genus, or whether it is a synonym and the molar teeth are the deciduous teeth of another genus of docodont.
Krusatodon is a genus of extinct docodont mammaliaform from the Middle Jurassic of the United Kingdom. It is known from the Forest Marble Formation, Kirtlington, in England, and also from a single molar tooth in the Kilmaluag Formation on the Isle of Skye, Scotland.
Simpsonodon is an extinct genus of docodontan mammaliaform known from the Middle Jurassic of England, Kyrgyzstan and Russia. The type species S. oxfordensis was described from the Kirtlington Mammal Bed and Watton Cliff in the Forest Marble Formation of England. It was named after George Gaylord Simpson, a pioneering mammalologist and contributor to the Modern Evolutionary Synthesis. A second species S. sibiricus is known from the Itat Formation of Russia, and indeterminate species of the genus are also known from the Balabansai Formation in Kyrgyzstan
Itatodon is an extinct genus of primitive mammaliaforms known from the Bathonian aged Itat Formation of Russia. The genus is named after the formation, with the species being named after Leonid Petrovich Tatarinov who described the first docodont from Asia. It is known from a holotype right lower molar and referred isolated right lower molar and fragment of the left lower molar. When it was first described, it was thought to be a docodontan, but one recent phylogenetic studies have assigned it, along with its close relative Paritatodon to Shuotheriidae, while others continue to consider it a docodont.
Delsatia is an early mammaliaform genus that lived during the Late Triassic and has been found in France. The type species, D. rhupotopi, was named in 1997. It was originally tentatively placed within the Docodonta, but subsequent studies disagree with this; Delsatia is seen by most as a basal mammaliaform. The holotype, MNHN.F.SNP408W, is an incomplete, isolated tooth.
