Shuotherium

Shuotherium is a fossil relative of the monotremes from the Jurassic. 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 teeth. Shuotherium, along with Pseudotribos has been placed in the Order Shuotheridia, Family Shuotheriidae as a sister taxon of the Australosphenida (see, Yinotheria). Its remains have been found in the Forest Marble of England as well as the Shaximiao Formation of China.

Tooth and Jaw Structure

In it lower molars, the talonid is situated in front of the trigonid, such a unique dental form is distinct from the typical tribosphenic pattern. In this "pseudotribosphenic" trait, the mesial cingulid is expanded to form a pseudotalonid, and its distal talonid is underdeveloped. It shares with Australosphenida a thin, slender dentary but differs from the nonmonotreme Ausktribosphenida by having more developed postdentary. Its dental formula has been reconstructed as: <p4, m3.

Expert Opinion

Kielan-Jaworowska et al. (2002) had this to say regarding the fossil:

"In our view, the most compelling evidence as to the affinities of Shuotherium lies in the structure of the last premolar, which shares striking similarities to that of Australosphenida."

"Lower molar structure of Shuotherium and Australosphenida is obviously quite different, and for this reason we do not place Shuotherium within this Gondwanan clade. Based on the limited evidence available, however, we suggest that Shuotherium is a viable sister-taxon to Australosphenida."

External links

• http://www.dinodata.org/index.php?option=com_content&task=view&id=8072&Itemid=143
• http://home.arcor.de/ktdykes/australo.htm

Further reading

Zofia Kielan-Jaworowska, Richard L. Cifelli, and Zhe-Xi Luo, Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure (New York: Columbia University Press, 2004), 214-215, 529.

See also

• Yinotheria
• Australosphenida
• Monotreme
• Pseudotribos
• Shuotheriidae