Acristatherium
Encyclopedia
Acristatherium yanensis is an extinct basal eutheria
n from the Early Cretaceous
(early Aptian
, approximately ) Lujiatun Bed of the Yixian Formation
. It was described on the basis of a single specimen (holotype
) from Beipiao
, Liaoning
, China
by Yaoming Hu, Jin Meng, Chuankui Li and Yuanqing Wang in 2010. The specimen comprises a partial skull
, 25 millimetre (0.984251968503937 in) long. It appears to possess a vestige of a septomaxilla, a feature only otherwise seen in non-mammalian therapsids.
Eutheria
Eutheria is a group of mammals consisting of placental mammals plus all extinct mammals that are more closely related to living placentals than to living marsupials . They are distinguished from noneutherians by various features of the feet, ankles, jaws and teeth...
n from the Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
(early Aptian
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...
, approximately ) Lujiatun Bed of the Yixian Formation
Yixian Formation
The Yixian Formation is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans 11 million years during the early Cretaceous period...
. It was described on the basis of a single specimen (holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
) from Beipiao
Beipiao
Beipiao is a city in Chaoyang prefecture, Liaoning province, in Northeast China. It has a population of 202,807. The main industry in the area is coal mining. With vertical shafts of almost 1000m, these are some of the deepest coal mines in China. The coal produced is used for coking...
, Liaoning
Liaoning
' is a province of the People's Republic of China, located in the northeast of the country. Its one-character abbreviation is "辽" , a name taken from the Liao River that flows through the province. "Níng" means "peace"...
, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
by Yaoming Hu, Jin Meng, Chuankui Li and Yuanqing Wang in 2010. The specimen comprises a partial skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
, 25 millimetre (0.984251968503937 in) long. It appears to possess a vestige of a septomaxilla, a feature only otherwise seen in non-mammalian therapsids.