Gurlin Tsav Skull
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The "Gurlin Tsav" skull is a currently unnamed
carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose nutrition and energy requirements are met by consumption of animal tissues (mainly mu ...
metatheria Metatheria is a mammalian clade that includes all mammals more closely related to marsupials than to placentals. First proposed by Thomas Henry Huxley in 1880, it is a more inclusive group than the marsupials; it contains all marsupials as wel ...
n fossil from the
Nemegt Formation The Nemegt Formation (also known as Nemegtskaya Svita) is a geological formation in the Gobi Desert of Mongolia, dating to the Late Cretaceous. The formation consists of river channel sediments and contains fossils of fish, turtles, crocodilians ...
of
Mongolia Mongolia is a landlocked country in East Asia, bordered by Russia to the north and China to the south and southeast. It covers an area of , with a population of 3.5 million, making it the world's List of countries and dependencies by po ...
. Composed of a single semi-complete skull, this specimen is notable in regards to the evolution and systematics of Metatheria as a whole, and thus nigh-omnipresent in phylogenetic analyses of this group.S. Bi, X. Jin, S. Li and T. Du. 2015. A new Cretaceous metatherian mammal from Henan, China. PeerJ 3:e896Guillermo W. Rougier; Brian M. Davis; Michael J. Novacek (2015). "A deltatheroidan mammal from the Upper Cretaceous Baynshiree Formation, eastern Mongolia". Cretaceous Research. 52, Part A: 167–177. doi:10.1016/j.cretres.2014.09.009.


Fossil location

The Gurlin Tsav skull, as the informal name indicates, comes from the Gurlin Tsav track in the
Nemegt Formation The Nemegt Formation (also known as Nemegtskaya Svita) is a geological formation in the Gobi Desert of Mongolia, dating to the Late Cretaceous. The formation consists of river channel sediments and contains fossils of fish, turtles, crocodilians ...
. This area represents fluvial deposits, and also heralds a few dinosaur specimens, such as a ''
Saurolophus ''Saurolophus'' (; meaning "lizard crest") is a genus of large hadrosaurid dinosaur from the Late Cretaceous period of Asia and North America, that lived in what is now the Horseshoe Canyon and Nemegt formations about 70 million to 66 million ...
'' skeleton.


Classification

The specimen was originally referred to
Deltatheroida Deltatheroida is an extinct group of basal metatherians that were distantly related to modern marsupials. The majority of known members of the group lived in the Cretaceous; one species, '' Gurbanodelta kara'', is known from the late Paleocene ( ...
, a clade of carnivorous metatherians rather common in the Cretaceous of
Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...
.
Zofia Kielan-Jaworowska Zofia Emilia Kielan-Jaworowska (25 April 1925 – 13 March 2015) was a Polish paleobiologist. In the mid-1960s, she led a series of Polish-Mongolian paleontological expeditions to the Gobi Desert. She was the first woman to serve on the executi ...
, Lev A. Nessov, On the metatherian nature of the Deltatheroida, a sister group of the Marsupialia, First published: January 1990Full publication history DOI: 10.1111/j.1502-3931.1990.tb01776.x
However, one study by Guillermo Rougier has found it to lack the group's synapomorphies and instead resemble the American
stagodontids Stagodontidae is an extinct family of carnivorous metatherian mammals that inhabited North America and Europe during the late Cretaceous, and possibly to the Eocene in South America. Description Currently, the family includes four genera, '' E ...
more closely. Posterior phylogenetic studies have indeed recovered this specimen as being closer to the Marsupialiformes line than to Deltatheroida. However, instead of being close to stagodontids, the Gurlin Tsav skull usually groups outside of a clade leading to
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
n metatherians (and, consequently, to
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 ...
s). It is nearly always an immediate outgroup to
sparassodont Sparassodonta (from Greek to tear, rend; and , gen. , ' tooth) is an extinct order of carnivorous metatherian mammals native to South America, related to modern marsupials. They were once considered to be true marsupials, but are now thought ...
s. Most recently, it has been found to group with sparassodonts and other
Paleocene The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...
non-marsupial metatherians from South America. It and these taxa from a group independent from not only Deltatheroida, but also a North American clade where true marsupials are nested as well as stagodontids.


References

{{Metatheria, M. Prehistoric metatherians Maastrichtian life Cretaceous mammals of Asia Cretaceous Mongolia Fossils of Mongolia Nemegt Formation Undescribed vertebrate species