''Amphitherium'' is an extinct genus of stem cladotherian

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

that lived during the Middle

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

. It was one of the first

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

mammals ever described. A recent phylogenetic study found it to be the sister taxon of '' Palaeoxonodon''. It is found in the Forest Marble Formation and the Taynton Limestone Formation.

Etymology

''Amphitherium'' comes from the Greek ''amphi'' meaning 'on both sides', and ''therion'' meaning 'wild beast'. This was in reference to de Blainville's incorrect belief that the original fossil jaw of this animal was not a mammal, but something in between mammals and reptiles.

History

The first jaws of mammals from the

- including ''Amphitherium'' - were found in the Stonesfield Slate, part of the Taynton Limestone Formation near Stonesfield in England.Rudwick, M.J.S. 2008
Worlds Before Adam
/ref> These were bought by a student of the British paleontologist

William Buckland William Buckland Doctor of Divinity, DD, Royal Society, FRS (12 March 1784 – 14 August 1856) was an English theologian, geologist and paleontology, palaeontologist. His work in the early 1820s proved that Kirkdale Cave in North Yorkshire h ...

. Although he thought the jaws were mammalian, the anatomist

Georges Cuvier Jean Léopold Nicolas Frédéric, baron Cuvier (23 August 1769 – 13 May 1832), known as Georges Cuvier (; ), was a French natural history, naturalist and zoology, zoologist, sometimes referred to as the "founding father of paleontology". Cuv ...

misidentified them as being from a

marsupial Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a r ...

mammal, '' Didelphis''. Later they were identified as being a new genus, and named ''Amphitherium''. It was first mentioned in the scientific literature alongside ''

Megalosaurus ''Megalosaurus'' (meaning "great lizard", from Ancient Greek, Greek , ', meaning 'big', 'tall' or 'great' and , ', meaning 'lizard') is an extinct genus of large carnivorous theropod dinosaurs of the Middle Jurassic Epoch (Bathonian stage, 166 ...

'', by William Buckland. It came from the Stonesfield Slate of Oxfordshire, England, and Buckland described it in 1824 as "''not less extraordinary''" than the dinosaur, but it was the larger fossil reptile that captured public imagination. Additional remains were recovered in the late 20th century from the Kirtlington Quarry and Watton Cliff, both part of the Forest Marble Formation Other early mammal discoveries included '' Amphilestes'', '' Phascolotherium'', and the mammal relative, '' Stereognathus''.

Classification

''Amphitherium'' is placed as a member of the clade Cladotheria. Some studies have placed it with '' Palaeoxonodon'', also known from the Middle Jurassic of Britain, as part of the clade Amphitheriidae. Cladogram after Panciroli et al. 2018:However, some studies have not found a close relationship with ''Palaeoxonodon''. Cladogram after Lasseron et al. 2022:

References

Cladotheria Bathonian genera Middle Jurassic mammals of Europe Jurassic England Fossils of England Fossil taxa described in 1838 Prehistoric mammal genera {{jurassic-mammal-stub