''Shuotherium'' is a fossil mammal known from Middle-

Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the nam ...

of the

Forest Marble The Forest Marble is a geological formation in England. Part of the Great Oolite Group, it dates to the late Bathonian stage of the Middle Jurassic.Weishampel, David B; et al. (2004). "Dinosaur distribution (Middle Jurassic, Europe)." In: Weisha ...

Formation of England,Sigogneau−Russell, D. 1998. Discovery of a Late Jurassic Chinese mammal in the upper Bathonian of England. Comptes Rendus de l’Académie des Sciences, Paris 327: 571–576 and the

Shaximiao Formation The Shaximiao Formation () is a Middle to Late Jurassic aged geological formation in Sichuan, China, most notable for the wealth of dinosaurs fossils that have been excavated from its strata. The Shaximiao Formation is exposed in and around the ...

Sichuan Sichuan (; zh, c=, labels=no, ; zh, p=Sìchuān; alternatively romanized as Szechuan or Szechwan; formerly also referred to as "West China" or "Western China" by Protestant missions) is a province in Southwest China occupying most of t ...

, China.M. Chow and T. H. V. Rich. 1982. Shuotherium dongi, n. gen. and sp., a therian with pseudo-tribosphenic molars from the Jurassic of Sichuan, China. Australian Mammalogy 54:127-142Kielan−Jaworowska, Z.; Cifelli, R.L.; Luo, Z.−X. (2002). "Dentition and relationships of the Jurassic mammal Shuotherium" (PDF). Acta Palaeontologica Polonica. 47 (3): 479–86 The original holotype is composed of a partial dentary and seven teeth (two which are incomplete). The holotypes for other species of this genus are solely represented by isolated molars. ''Shuotherium'', along with ''

Pseudotribos ''Pseudotribos'' ("false chewing") is an extinct genus of mammal that lived in Northern China during the Middle Jurassic some , possibly more closely related to monotremes than to theria (placental and marsupial Marsupials are any members of ...

'' has been placed in the family

Shuotheriidae Shuotheriidae is a small family of Jurassic mammals whose remains are found in China, England and possibly Russia. They have been proposed to be close relatives of Australosphenida, the group that contains living monotremes, together forming the ...

as a sister taxon of the

Australosphenida The Australosphenida are a clade of mammals, containing mammals with tribosphenic molars, known from the Jurassic to Mid-Cretaceous of Gondwana. They are thought to have acquired their tribosphenic molars independently from those of Tribospheni ...

(see,

Yinotheria Yinotheria is a proposed basal subclass clade of crown mammals uniting the Shuotheriidae, an extinct group of mammals from the Jurassic of Eurasia, with Australosphenida, a group of mammals known from the Jurassic to Cretaceous of Gondwana, which ...

),Kielan-Jaworowska, Zofia; Cifelli, Richard L.; Luo, Zhe-Xi 2004. Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure. New York: Columbia University Press. making it a relative of modern

monotreme Monotremes () are prototherian mammals of the order Monotremata. They are one of the three groups of living mammals, along with placentals (Eutheria), and marsupials (Metatheria). Monotremes are typified by structural differences in their brains ...

s. However, some studies place it and other shuothereres as closer to

theria Theria (; Greek: , 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. ...

n mammals.Tom Rich, Patricia Vickers Rich, Palaeobiogeography of Mesozoic Mammals – Revisited, Article · January 2012 DOI: 10.1007/978-90-481-3428-1_32

Description

In the lower molars, the

talonid The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...

is situated in front of the

trigonid The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...

, such a unique dental form is distinct from the typical tribosphenic pattern. In this "pseudotribosphenic" trait, the mesial

cingulid A cingulid is a term used when describing teeth, it refers to a ridge that runs around the base of the crown of a lower tooth (the equivalent on the upper teeth is the cingulum). The presence or absence of a cingulid is often a diagnostic featur ...

is expanded to form a pseudotalonid, and its distal talonid is underdeveloped. It shares with Australosphenida a thin, slender lower jaw but differs from the non-monotreme Ausktribosphenida by having more developed postdentary trough. Its dental formula has been reconstructed as: p4, m3 (four premolars, three molars). had this to say regarding the fossil:

Notes

References

* * * * * * {{Taxonbar, from=Q7505192 Jurassic mammals of Europe Jurassic mammals of Asia Prehistoric mammal genera Fossil taxa described in 1982 Taxa named by Zhou Mingzhen Taxa named by Tom Rich