Shuotherium
Encyclopedia
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.
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
. 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
Pseudotribos
Pseudotribos is an extinct genus of mammal from the Middle Jurassic some 165 million years ago of China.-External links:*...
has been placed in the Order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Shuotheridia, Family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Shuotheriidae
Shuotheriidae
Shuotheriidae is the sole family within the order Shuotheridia, it includes Pseudotribos and Shuotherium.-Further reading:Zofia Kielan-Jaworowska, Richard L. Cifelli, and Zhe-Xi Luo, Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure , 214-215....
as a sister taxon of the Australosphenida
Australosphenida
The Australosphenida are a clade of mammals. Today, living specimens exist only in Australia and New Guinea with only five surviving species, but fossils have been found in Madagascar and Argentina...
(see, Yinotheria). Its remains have been found in the Forest Marble
Forest Marble
The Forest Marble is a geological formation in Europe. It dates back to the Middle Jurassic.-Ornithischians:-Saurischians:-References:...
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: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
- AustralosphenidaAustralosphenidaThe Australosphenida are a clade of mammals. Today, living specimens exist only in Australia and New Guinea with only five surviving species, but fossils have been found in Madagascar and Argentina...
- MonotremeMonotremeMonotremes are mammals that lay eggs instead of giving birth to live young like marsupials and placental mammals...
- PseudotribosPseudotribosPseudotribos is an extinct genus of mammal from the Middle Jurassic some 165 million years ago of China.-External links:*...
- ShuotheriidaeShuotheriidaeShuotheriidae is the sole family within the order Shuotheridia, it includes Pseudotribos and Shuotherium.-Further reading:Zofia Kielan-Jaworowska, Richard L. Cifelli, and Zhe-Xi Luo, Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure , 214-215....